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  • General Chemistry  (11,144)
  • Life and Medical Sciences  (5,775)
  • 1995-1999  (10,766)
  • 1975-1979  (6,153)
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  • 1
    Electronic Resource
    Electronic Resource
    “Embroidered” Square Pyramidal Coordination Caps for Nickel(II): Mono-, Di- and Tetrafunctionalisation of a Tetrapodal Pentadentate Ligand with an NN4 Donor Set (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2147-2156 
    Details
    ISSN: 1434-1948
    Keywords: Tetrapodal pentadentate ligand ; Ligand periphery ; Polydentate amine complex ; Nickel ; Podand ; Schiff base ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The tetrapodal pentaamine ligand 2,6-bis(1′,3′-diamino-2′-methylprop-2′-yl)pyridine (1), which contains four equivalent primary amino groups, can be derivatised partly or completely by Schiff base condensation with suitable carbonyl compounds. The new ligands thus obtained are mononucleating, as shown by the X-ray crystal structures of their respective nickel(II) complexes. Reaction of 1 with 1 equiv. of salicylaldehyde and subsequent reduction allows the selective modification of one of the four sidearms. The resulting ligand 2 is hexadentate and uninegative in its nickel(II) complex {[(2)Ni]PF6} (3) with both the secondary amine and the phenoxide functionalities coordinated to the metal centre. The unreduced Schiff base form of the ligand, 4, does not form a complex with nickel(II) as readily, and only a small quantity of the mixed salt {[(4)Ni][(1)Ni(H2O)](Br)2(PF6)} (5)has been obtained. While the overall coordination of 4 resembles that of 2, there is considerably more strain in the appended chelate ring, due to the presence of the C=N double bond. Modification of one arm in 1 can also be achieved by condensation with 1 equiv. of acetylacetone, to give the new ligand 6 which, likewise, is hexadentate in its NiII complex {[(6)Ni](PF6)2} (7). In this case, however, the N/O-functional sidearm is not deprotonated. Rather, it is coordinated as the keto-imine tautomer, making 7 a rare example of a metal complex containing this structural fragment. Two-fold functionalisation of 1 is observed upon reaction with acetone, regardless of whether the ketone is present in stoichiometric amounts or in excess, to give the pentadentate ligand 8with two diagonally juxtaposed isopropylidene-imine units. The complex isolated with this ligand {[(8)Ni](PF6)2} (9) contains pentacoordinate NiII, the sixth coordination site being blocked by the rigidly positioned isopropylidene groups. When reacted with 4 equiv. of trans-cinnamaldehyde, all the primary amino groups in 1 condense to give the four-fold Schiff base 10, which acts as a pentadentate podand towards nickel(II). In this complex, {[(10)Ni(OH2)]Br2} (11), an aqua ligand completes the coordination octahedron. All ligands are stable towards hydrolysis when coordinated to the metal, despite the presence of alkyl-imine groups in some cases.
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  • 2
    Electronic Resource
    Electronic Resource
    Control of Reactivity of Dinuclear Nickel(II) Amine-Thiolate Complexes (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2157-2166 
    Details
    ISSN: 1434-1948
    Keywords: Septadentate N5S2-ligand ; Dinuclear complexes ; Nickel ; Reactivity ; Redox chemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coordination chemistry of a series of dinickel complexes of the new septadentate amine-thiolate ligand N,N′-bis[2-thio-3-aminomethyl-5-tert-butylbenzyl]diethylenetriamine, H29, has been investigated in the context of ligand binding and oxidation state changes. The complexes [Ni2(9)(L)][ClO4]2 (10), [Ni2(9)(Cl)][Cl] (11), [Ni2(9)(L)][BPh4]2 (12), and [Ni2(9)(NCS)][OH·OH2] (13) have central N2Ni(μ-SR)2NiN′3L cores [L = labile solvent molecule (10, 12), Cl- (11), and NCS- (13)] composed of dithiolate bridged planar NiN2S2 and six-coordinate NiN′3S2L units. This is demonstrated for 11 and 13 by crystal structure determinations and for 10 and 12 by UV/Vis spectroscopy and room temperature magnetic susceptibility measurements. Complexes 10, 11, or 12 readily add other co-ligands at the NiN′3S2L fragment by substitution of the solvent molecule L (10, 12) or the chloride substituent (11). The overall structure of the parent complexes is not affected by the substitution reactions. An electrochemical study has shown that complex 10 undergoes two successive one-electron oxidations at +0.88 and +0.41 V vs SCE. The oxidized species are not thermally stable, but electronic absorption spectra and EPR spectra are indicative of the presence of NiIII species.
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  • 3
    Electronic Resource
    Electronic Resource
    Novel Synthesis of Macrocyclic Amine-Thiophenolate Ligands: X-ray Crystal Structure of a Ni4 Complex of an N8S4 Ligand (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2167-2172 
    Details
    ISSN: 1434-1948
    Keywords: Macrocyclic compounds ; Amine-Thiolate Donors ; Polynuclear Complexes ; Nickel ; Condensation reactions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel route to macrocyclic amine-thiophenolate ligands is described. The new, air-stable thiophenolate precursor 1,2-bis(4-tert-butyl-2,6-diformyl-phenylsulfanyl)ethane (4) is readily condensed with two equivalents of 1,2-ethanediamine or 1,3-propanediamine under medium to high dilution conditions to give 2 × 4 condensation products. The smaller 1 × 2 macrocyclic compounds are not produced under these conditions. Subsequent reduction with NaBH4 (reduction of imine groups) and Na/NH3 (reductive cleavage of aryl-alkylsulfides) provides the 36- and 40-membered amine-thiophenolate ligands H46a and H46b. The macrocyclic compounds are versatile ligands for the preparation of polynuclear transition metal complexes. With divalent nickel H46a forms the di- and tetranuclear complexes [Ni2(6a)] (7) and [Ni4(6a)][ClO4]4 (8). Reaction of 8 with four equivalents of NH4SCN yields the novel isothiocyanate complex [Ni4II(6a)(NCS)4]·10MeCN (9). The structure consists of well-separated molecules of the tetranuclear complex [NiII4(6a)(NCS)4] (Ci symmetry). Two symmetry-related binuclear [N2Ni(μ2-SR)2NiN4] fragments composed of thiolate-bridged distorted planar {N2S2Ni}- and distorted cis-octahedral {(SCN)2N2S2Ni} units reside within the cavity of the macrocycle. The intramolecular distance between the two binuclear units is 6.144(1) Å.
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  • 4
    Electronic Resource
    Electronic Resource
    The Mono-, Di-, and Tri([5]trovacenyl)boranes: A Study of Intermetallic Communication Across an sp2-Hybridized Boron Atom (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2173-2185 
    Details
    ISSN: 1434-1948
    Keywords: EPR spectroscopy ; Metallocenylboranes ; Organovanadium radicals ; Redox chemistry (CV) ; X-ray diffraction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The paramagnetic complexes di(mesityl)([5]trovacenyl)borane (5·), (mesityl)di([5]trovacenyl)borane (6··), and tri([5]trovacenyl)borane (7···) were prepared from [5]trovacenyllithium, (η5-C7H7)V(η5-C5H4Li), and (Mes)2BF, (Mes)BF2, and BF3, respectively. The propeller-shaped species 5·, 6··, and 7··· were subjected to X-ray diffraction with the aim of possibly correlating the twist angles with intramolecular intermetallic communication. Cyclic voltammetry points to successive vanadium-centered oxidation processes and boron-centered reduction, a small redox splitting δE1/2[(2+/+), (+/0)] being observed for 6··. According to EPR spectroscopy, performed in fluid solution, the exchange interaction J in the diradical 6·· approaches the fast-exchange region and is attenuated significantly by quaternization at boron in [6··-nBu]-. Although EPR spectroscopy of the triradical 7··· also indicates an extensive exchange interaction, the exchange parameters, derived from spectral simulation, follow the gradation J(7···) ≈ 1/3 J(6··). The magnetic susceptibility of 6·· and 7··· follows the same trend. As expected, compound 7··· exhibits spin frustration because it contains three antiferromagnetically coupled S = 1/2 systems that are arranged in an equilateral triangle.
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  • 5
    Electronic Resource
    Electronic Resource
    Chiral Chelate Ligands Based on a Neopentane Framework; Introducing Indenyl and Fluorenyl Donor Groups (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2187-2199 
    Details
    ISSN: 1434-1948
    Keywords: Ansa compounds ; Cp-derived chelate ligands ; Neopentane chemistry ; Spiro compounds ; Tripodal ligands ; Cyclopentadienyl compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The neopentane-derived functionalized oxetane O(CH2)2C(CH3)(CH2OMs), 1, reacts with indenyllithium (LiInd) or fluorenyllithium (LiFlu) to produce the derivatives O(CH2)2C(CH3)(CH2R) (R = indenyl, fluorenyl), 2. The oxetane ring of 2 undergoes nucleophilic ring-opening by reaction with LiPR′2 to give the chiral chelate ligands (HOCH2)(CH3)C(CH2R)(CH2PR′2) (R = indenyl, fluorenyl), 5. Nucleophilic ring-opening by LiInd or LiFlu is possible too, resulting in the functionalized ansa-Cp ligands (HOCH2)(CH3)C(CH2R)(CH2R′) (R, R′ = indenyl, fluorenyl), 12. Electrophilic ring-opening of 2 with HBr to give (HOCH2)(CH3)C(CH2R)(CH2Br) (R = indenyl, fluorenyl), 3, is also possible. The alcohol function of 3 may be activated directly, whereas activation of this group in 5 is only possible after BH3 protection of the phosphane function. The mesylates (MsOCH2)(CH3)C(CH2R)(CH2Br) (R = indenyl, fluorenyl), 4, undergo, under basic conditions, spiro cyclization to produce spirocyclobutane derivatives 9 with the α-carbons of the five-membered cycles acting as the spiro centres. Substitution of the mesylate group of 4 by PR2 nucleophiles is therefore not possible. Ansa-Cp derivative (MsOCH2)(CH3)C(CH2Ind)(CH2Flu), 12c also reacts with LiPPh2 with spiro cyclization to produce 9d, instead of giving the substitution product. Tripodal ligands (CH3)C(CH2R)(CHPPh2)2 (R = indenyl, fluorenyl), 11, are accessible by the reaction of (MsOCH2)(CH3)C(CH2PPh2)2 with LiInd or LiFlu. All compounds are fully characterized by the usual spectroscopic and analytical techniques including single-crystal X-ray analyses in several cases.
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  • 6
    Electronic Resource
    Electronic Resource
    An Inorganic Helix [Mn(IPG)(MeOH)]n[PF6]n[ (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2201-2207 
    Details
    ISSN: 1434-1948
    Keywords: Carboxylate syn-anti ; N-centered tripodal ligand ; Manganese ; Imidazole ; Helicoïdal inorganic chiral chain ; Magnetism ; π-π interaction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of an infinite inorganic chain consisting of MnII and an N-centered tripodal ligand N,N-(2-pyridylmethyl)[(1-methylimidazol-2-yl)-methyl]glycinate is presented. It exhibits a chiral helical structure with a pitch of two monomeric units (each monomeric unit containing one Mn atom). Each manganese is connected to its neighbor through a carboxylate bridge in a syn-anti geometry. Around each manganese center, two carboxylates bind in a cis geometry. This peculiar bridging geometry (syn-anticis) provides a broken-line chain, running in a zig-zag manner along the b axis of the P21 space group. The magnetic properties have been investigated. They show a pseudo-2D magnetic structure, with one major pathway along the chain and an inter-chain minor one. The intrachain coupling is a weak antiferromagnetic interaction (J/k = -0.25). This low value is entirely consistent with the geometry of the bridge. The interchain coupling is a weaker antiferromagnetic coupling (J′/k = -0.11) and could be mediated through π-π interactions between pyridine and imidazole from two adjacent helixes.
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  • 7
    Electronic Resource
    Electronic Resource
    Syntheses, Molecular Structures, and Bonding of Molybdenum and Tungsten Calix[4]arene Imido Complexes (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2221-2231 
    Details
    ISSN: 1434-1948
    Keywords: Calixarenes ; Inclusion compounds ; Imido Complexes ; Molybdenum ; Tungsten ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses, spectroscopic properties, molecular structures, and bonding of novel calix[4]arene imido compounds are described. Treatment of M(NtBu)2(NHtBu)2Ia (M = Mo), Ib (M = W) or M(NMes)2Cl2(dme) IIa (M = Mo), IIb (M = W) (Mes = 2,4,6-Me3-C6H2) with p-tBu-calix[4]arene LH4 affords calix[4]arene metal complexes LM(NR) 1a, b (M = Mo, W; R = tBu) and 2a, b (M = Mo, W; R = Mes). Analytical and spectroscopic data are consistent with monomeric structures for 1 and 2, retaining a local C4v symmetry for the calix[4]arene metal fragment. These complexes are well-suited to bind small molecules like acetonitrile, tBu-isonitrile, or water within their macrocyclic pockets. The spectroscopic data of some inclusion compounds and the crystal structures of LMo(NtBu)(NCMe) 1a(NCMe), LW(NtBu)(OH2) 1b(OH2), LW(NtBu)(CNtBu) 1b(CNt Bu), LMo(NMes)(NCMe) 2a(NCMe), and LW(NMes)(NCMe) 2b(NCMe) are reported. All complexes contain a group VI metal imido [M=NR] moiety mounted on the phenoxide rim of the calix[4]arene ligand as well as an incorporated guest molecule within the cavity. Some insights into the structures of complexes of the type L′W(NR′) (L′ = p-H-calix[4]arene; R′ = H, Me) and into bonding in these compounds are provided by density functional theory, applying the B-P86 density functional and an all SVP basis set within the RI-J-DFT approximation. At least one π bond is of importance for calix[4]arene-metal bonding in these compounds. The metal-imido bond can be described as a triple bond. A geometrically optimized minimum structure of L′W(NMe) 4 shows a calix[4]arene ligand only slightly distorted from a local C4v symmetry and an almost linear tungsten-imido moiety.
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  • 8
    Electronic Resource
    Electronic Resource
    Synthesis and Characterisation of New Arsonium Salts and Crystal Structures of Trimethylarsonium Undecafluorodiarsenate (CH3)3AsH+As2F11- and Trimethylarsonium Hexafluoroantimonate (CH3)3AsH+SbF6- (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2249-2254 
    Details
    ISSN: 1434-1948
    Keywords: Arsonium salts ; Superacidic systems ; Structure elicidation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of trimethylarsane in the superacidic systems hydrogen/fluoride antimony pentafluoride and hydrogen fluoride/arsenic pentafluoride leads to trimethylarsonium fluorometallates. These salts are stable up to 60 °C and 5 °C, respectively. Structures were successfully elucidated in the cases of trimethylarsonium undecafluorodiarsenate and trimethylarsonium hexafluoroantimonate. (CH3)3AsH+As2F11- crystallizes in the monoclinic space group P21/n with four formula units per unit cell with the dimensions a = 7.362(1), b = 12.589(1), c = 13.598(1) Å and β = 95.37(1)°. (CH3)3AsH+SbF6- crystallizes in the monoclinic space group P21/m with four formula units per unit cell with the dimensions a = 8.313(1), b = 8.855(1), c = 13.285(1) Å and β = 94.358(1)°.
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis and Characterisation of a Dioxo-μ-Oxo Molybdenum Dimer: An Unusual case of a μ-Oxo Conformational Equilibrium (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2255-2259 
    Details
    ISSN: 1434-1948
    Keywords: Molybdenum ; μ-Oxo ; Conformational equilibrium ; X-ray diffraction ; NMR spectroscopy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new thiocyanatomolybdenum(VI) dioxo-μ-oxo complex dimer bearing a 4,4′-di-tert-butyl-2,2′-bipyridine ligand (2) is shown to exist in the crystal cell unit as a meso (Mo-O-Mo angle of 180°) and d,l, pair (Mo-O-Mo angle of 155.7°). These conformers are in equilibrium in solution and have been observed clearly by 1H NMR spectroscopy.
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  • 10
    Electronic Resource
    Electronic Resource
    Selective Lithium Complexation by Photoactive Aza-Cages Bearing the Anthracene Function (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2261-2268 
    Details
    ISSN: 1434-1948
    Keywords: Macrocycles ; Lithium ; Fluorescence ; Cryptands ; Coordination ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three aza-cages with the anthracene-containing photoactive groups L1, L2, and L3 have been synthesized. All compounds are able to selectively encapsulate a lithium ion and solid complexes have been isolated. The formation equilibria have been investigated by UV/Vis and 1H, 13C and 7Li NMR spectroscopic techniques. The fluorescence emission of both free ligands and lithium complexes have been investigated. Results indicate that the CHEF (chelation enhancement of the fluorescence) effect obtained by lithium coordination exits although lower than that occurring upon full protonation.
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  • 11
    Electronic Resource
    Electronic Resource
    Synthesis, Structure, Spectroscopy, and Magnetism of Unique Propeller-Type Linear Trinuclear CuII Complexes with In-situ Prepared Formamidine Ligands (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2269-2275 
    Details
    ISSN: 1434-1948
    Keywords: Copper ; Trinuclear complexes ; Formamidines ; Magnetism ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three new copper(II) linear trinuclear compounds are reported, all of which were synthesized in-situ, with the general formula [Cu3(L)4](CF3SO3)2(Y)x, where L is the dehydronated ligand: N,N′-bis(pyridine-2-yl)formamidine (abbreviated as Hpdf), N,N′-bis(pyrimidine-2-yl)formamidine (abbreviated as Hpmf) and N,N′-bis(5-methylpyridine-2-yl)formamidine (abbreviated as Hmpdf), Y = EtOH or H2O and x = 0.5-1.5. The compounds were characterized by X-ray diffraction, IR, LF, and EPR spectroscopy and by magnetic susceptibility down to 4 K. The structure of the compound [Cu3(pmf)4](CF3SO3)2(H2O)1/2 was determined by X-ray crystallography; it was found to crystallise in the triclinic space group P-1 with a = 8.529(5), b = 15.760(5), c = 19.639(5) Å, α = 101.793(5), β = 101.263(5), γ = 102.389(5)°, Z = 2. The structure [Cu-Cu-Cu angle 174.96(11)°] consists of four nearly flat molecules of the ligand, which contribute to the propeller-type structure around the Cu-Cu-Cu axis. A strong antiferromagnetic interaction between the CuII ions is observed with calculated J values, based on the Hamiltonian H = -2J(S1·S2 + S2·S3) - 2J′·S1·S3, of -174(1) cm-1, -120(1) cm-1, and -167(1) cm-1 for the compounds studied with L = pdf, pmf, and mpdf, respectively. These values are in agreement with an S = 1/2 ground state below temperatures of 120-160 K.
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  • 12
    Electronic Resource
    Electronic Resource
    Synthesis and Structure of Trinuclear Boryloxycarbyne Complexes (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2277-2281 
    Details
    ISSN: 1434-1948
    Keywords: Boron ; Iron ; Nickel ; Carbyne complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The μ3-boryloxycarbyne complexes [{Fe(CO)3}3{μ3-COBCl{NtBu(SiMe3)}}2] (1) and [{(η5-C5H5)Ni}3{μ3-COBX(NR2)}μ3-CO] (2a: NR2 = NtBu(SiMe3), × = Cl; 2b: NR2 = N(SiMe3)2, × = Cl; 2c: NR2 = NMe2, × = BNMe2Cl) were obtained by reaction of the anionic complexes K2[{Fe(CO)3}3{μ3-CO}2] and K[{(η5-C5H5)Ni(CO)] with the corresponding chloroboranes Cl2BNR2 {NR2 = NtBu(SiMe3), N(SiMe3)2}, or 1,2-dichlorodiboranes(4) B2(NMe2)2Cl2, respectively. The products are formed by a nucleophilic attack of the CO oxygen atom at the boron centres with subsequent salt elimination. All compounds were characterized by IR and multinuclear NMR spectroscopy, and the structures of 1 and 2c in the solid state were determined by single-crystal X-ray diffraction studies.
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  • 13
    Electronic Resource
    Electronic Resource
    Predetermined Chirality in Mono- and Dinuclear Cyclometalated Rhodium(III) Complexes (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1271-1279 
    Details
    ISSN: 1434-1948
    Keywords: Chirality ; Dinuclear complexes ; Rhodium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dinuclear and polynuclear metal complexes with octahedral centers coordinated to di- or polydentate ligands are often obtained as complicated mixtures of various stereoisomers. Stereospecific synthesis of such species is therefore of high current interest. Chiral derivatives of pyridine can be used for this purpose. Dinuclear μ-chloro-bridged RhIII complexes with two didentate, cyclometalated thienylpyridine-type ligands at each metal center are formed stereoselectively when pinene groups are fused to the pyridine rings. The two octahedral RhIII centers have homochiral configurations, ΔΔ and ΛΛ. The heterochiral diastereomer ΔΛ is not observed. With (8R,10R)-2-(2′-thienyl)-4,5-pinenopyridine [Hth4,5-(R,R)ppy] the ΔΔ to ΛΛ ratio is 9:1 when the separation eluent contains NaCl. Modeling the ΛΛ and the ΔΛ isomers of the dinuclear species shows crowding of the pinene groups in both cases; however, the strain can be released by relatively small distortions only in the case of the ΛΛ isomer. NO3- cleaves the dichloro bridge, yielding the mononuclear species Δ[Rh(L2)2(NO3)] (2) in a completely stereoselective manner when NaCl is replaced by KNO3 in the eluent mixture. The molecular structure has been determined by X-ray structure analysis for both the ΔΔ and the mononuclear complex Δ[Rh(L2)2(NO3)] (2) in order to confirm the configuration at the metal center. 1H-NMR, 13C-NMR and CD spectra were measured and the latter shows that the CD activity is solely due to the chirality at the metal center.
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  • 14
    Electronic Resource
    Electronic Resource
    A Density Functional Study of the Dimerization of Phosphaalkynes in the Presence of Transition Metal Fragments (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1281-1289 
    Details
    ISSN: 1434-1948
    Keywords: Phosphaalkynes ; Dimerization mechanism ; Diphosphacyclobutenes ; Density functional theory ; Ab initio calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dimerization of phosphaalkynes (R-C≡P, R = H, Me, tBu) without and with the presence of transition metal fragments, including CpCo (Cp = cyclopentadienyl) and COT-Ti (COT = cyclooctatetraene), has been probed using density functional theory calculations (B3LYP with different basis sets). MP2 and CCSD(T) calculations were also performed for the [H2C2P2] systems. In an attempt to address the exciting controversy and uncertainty about phosphaalkyne dimerization, a number of dimer formation mechanisms proposed in the literature have been examined. Some new and plausible intermediates have also been identified.
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  • 15
    Electronic Resource
    Electronic Resource
    Roles of π-Alkyne, Hydride-Alkynyl, and Vinylidene Metal Species in the Conversion of Alkynes into Vinylidene: New Theoretical Insights (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1315-1324 
    Details
    ISSN: 1434-1948
    Keywords: Ab initio calculations ; EHMO ; Vinylidene complexes ; Cobalt ; Rhodium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The transformation of acetylene into vinylidene, as promoted by the metal fragment [(pp3)Co]+ [pp3 = P(CH2CH2PPh2)3], is unimolecular and features the hydride-acetylide species as an intermediate. The paper describes a detailed ab initio study of the reaction, in particular with regard to the step involving 1,3-H shift. The best computational results are obtained by mimicking the pp3 ligand with actual ethylenic chains rather than with single PH3 molecules. The keypoints along the two-step reaction path (π-acetylene, hydride-acetylide, and vinylidene complexes, as well as intermediate transition states) have been optimized for CoI and RhI derivatives at the MP2 level. For the fragment [(pp3)Co]+, the barrier associated with transformation of the hydride-acetylide intermediate to vinylidene (20.6 kcal/mol) is easier to surmount compared to that for reversion to the reactants (28.6 kcal/mol). The situation is reversed for the analogous RhI system, with the initial π-acetylene adduct being slightly more stable. Although higher in energy, the hydride-acetylide species is the experimentally detected product of the reaction of acetylene with the fragment [(pp3)Rh]+. The salient chemical aspects of the 1,3-H shift are discussed in terms of perturbation theory arguments. Parallel EHMO calculations, which have provided a relatively good consistency with the ab initio results, allow the proposal of an orbital rationale for the mode of migration of the hydride ligand along the substantially linear Co-Cα-Cβ grouping.
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    Oxygen Transfer from Chromyl Chloride to Alkynes and Allene - IR-Spectroscopic Identification of η1-Ketene and Cyclopropanone Complexes of O=CrCl2 (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1335-1342 
    Details
    ISSN: 1434-1948
    Keywords: Photolysis ; Alkynes ; Matrix isolation ; DFT ; Oxygenations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photolytically-induced reactions of chromyl chloride with acetylene and but-2-yne (dimethylacetylene) in low-temperature argon matrices yield end-on ketene and dimethylketene complexes of O=CrCl2, respectively. The product formation probably results from an electrophilic attack of a Cr=O linkage on the C≡C triple bonds, leading to radical-like transition states or intermediates, which subsequently rearrange through 1,2-H or 1,2-methyl shifts. Consequently, allene is attacked at its central carbon and the allyl radical thus generated undergoes subsequent ring-closure to give a cyclopropanone complex of O=CrCl2.
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    Synthesis, Crystal Structure, Spectroscopy, and Theoretical Investigations of Tetrahedrally Distorted Copper(II) Chelates with [CuN2S2] Coordination Sphere (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1393-1403 
    Details
    ISSN: 1434-1948
    Keywords: Copper chelates ; EPR spectroscopy ; Electronic structure ; Schiff base ligands ; Structure elucidation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of tetrahedrally distorted copper(II) complexes with thiolate and imine coordination were synthesized. Schiff bases derived from 4-benzoyl-3-methyl-1-phenyl-2-pyrazoline-5-thione and various diamines were used as tetradentate ligands to obtain tetrahedrally distorted metal chelates with [CuN2S2] complex units. Crystal structures of the complexes 1, 2, 5 and 6 and of ligand H25 have been determined by means of single-crystal X-ray structure analysis. The structure data show a strong influence of the diamine building blocks on the tetrahedral distortion of the copper(II) complexes. Results of Extended Hückel LCAO calculations correlate strongly with structural, electrochemical, UV/Vis- and EPR-spectroscopic features obtained experimentally. The calculations confirm for the whole complex series a strong delocalization of the frontier orbitals. The highest fully occupied molecular orbital shows a weak contribution, resulting from thiolate donor atoms, whereas the antibonding singly occupied molecular orbitals (SOMOs) are distributed between the copper(II) centre (ca. 35-40%) and the N2S2 donor set. The SOMO energy significantly lowers with increasing tetrahedral distortion of the coordination sphere. The influence of the tetrahedral distortion of copper(II) complexes on redox potentials, UV/Vis and EPR spectra is discussed.
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    Transition-Metal Complexes of the Optically Active Cyclopentadienyl Ligand PinCp*: Crystal Structure of (SRe)-(η5-PinCp*)Re(NO)(PPh3)[CONHCH(CH3)C10H7] (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1497-1505 
    Details
    ISSN: 1434-1948
    Keywords: Half-sandwich complexes ; Molybdenum ; Optically active complexes ; Rhenium ; Tungsten ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of (η5-PinCp*)Re(CO)3 [PinCp* = tetramethyl(pinanyl)cyclopentadienyl] is described. Successive substitution of two CO ligands by NO+ and PPh3 generates a 1:1 diastereomeric mixture of chiral-at-metal [(SRe)/(RRe)-(PinCp*)Re(CO)(NO)(PPh3)]BF4. The diastereomers are converted with sodium methoxide into the derivative “esters” (SRe)/(RRe)-(PinCp*)Re(COOCH3)(NO)(PPh3), and then with (+)-(R)-(1-naphthylethyl)amine to the “amides” (SRe)/(RRe)-(PinCp*)Re(NO)(PPh3)[CONHCH(CH3)C10H7] [(SRe)/(RRe) = 1:1]. Fractional crystallisation separates the (SRe) isomer with an optical purity of 〉 98%. The latter compound has been characterized by X-ray structure analysis. By treating the (SRe)-amide with CF3CO2H and NaBF4, (SRe)-(PinCp*)Re(CH3)(NO)(PPh3) can be generated. Protolysis of this compound with HBF4/Et2O in CD2Cl2 at -78 °C leads to the solvent-stabilized complex (SRe)-[(PinCp*)Re(NO)(PPh3)(ClCD2Cl)]+BF4-. The thermal and configurational stability of this chiral Lewis acid is investigated at various temperatures. The syntheses of [PinCp*RhCl2]2, PinCp*TiCl3 and PinCp*M(CO)2(NO) (M = Mo, W) are also described. Starting with PinCp*M(CO)2(NO), the relatively stable 16-VE complexes PinCp*MCl2(NO) and PinCp*W(CH2SiMe3)2(NO) are synthesized.
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    Modified Bipyridines: 5,5′-Diamino-2,2′-bipyridine Metal Complexes Assembled into Multidimensional Networks via Hydrogen Bonding and π-π Stacking Interactions (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1507-1521 
    Details
    ISSN: 1434-1948
    Keywords: 2,2′-Bipyridines ; Chelate complexes ; Hydrogen bonding ; π-π stacking ; Crystal structure ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new synthetic route for the synthesis of 5,5′-diamino-2,2-bipyridine (5) based on the coupling of 2-chloro-5-aminopyridine in the presence of NiCl2 × 6 H2O/PPh3/Zn in dimethylformamide is described. The reactions of the potentially ambidentate ligand 5 with salts of the transition metals Mn, Fe, Ni, Cu, Zn, Ag, and Cd gave a variety of 13 metal-ligand complexes depending on the anion, the crystallization conditions and the metal-to-ligand ratio. The complexes obtained were characterized by thermal analyses, NMR including 113Cd-NMR, IR, and for the iron complex 57Fe-Mößbauer spectroscopy. The structure of eight of the compounds was elucidated by X-ray crystallography. All of these metal complexes show a bipyridine-metal coordination. The amino functionality was never involved in metal coordination. The intermolecular arrangement is dictated by hydrogen bonding from the amino functionality and by π-π stacking of the bipyridine rings.Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2005/1999/99078_s.pdf or from the author.
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    Structural and Functional Investigations on Diiron Complexes: Catalase-Like Activity and Mechanistic Studies on the Formation of (μ-Peroxo)diiron(III) Adducts (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1537-1543 
    Details
    ISSN: 1434-1948
    Keywords: Iron(III) ; Peroxo Complexes ; Kinetics ; Hydrogen Peroxide ; Catalase ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The new diiron complex [Fe2(tbpo){O2As(CH3)2}(CH3O)(CH3OH)](ClO4)3 · 5 CH3OH · 2 H2O (1) containing a (μ-alkoxo)(μ-dimethylarsinato)diiron(III) core was synthesized using the heptadentate ligand N,N,N′,N′-Tetrakis(2-benzimidazolylmethyl)-1,3-diamino-2-propanol (Htbpo). The complex was characterized structurally by X-ray crystallography. 1reproduces the coordination mode and the stoichiometry of the proposed purple acid phosphatase-arsenate inhibitor complex. More importantly, 1 is a good functional model for the activation of small molecules, since the solvent molecule in the coordination sphere of each iron ion can be substituted very easily by a small substrate molecule. This is confirmed by the comparatively high pH-dependent catalase-like activity of 1. In order to study the influence of the cacodylate bridge on the formation of the metastable adduct with hydrogen peroxide, the analogous hydroxo-bridged complex [Fe2(tbpo)(OH)(NO3)2](NO3)2 · CH3OH · 2 H2O (2) was employed. The reactions of 1and 2 with H2O2 were studied as a function of [H2O2], pH, temperature, and pressure, and the kinetic results including the activation parameters are reported. In the case of compound 2 the reaction proceeds in one step, and the observed first order rate constant, kobs, shows a linear dependence on the hydrogen peroxide concentration with a zero intercept. For complex 1 the kinetic traces could be fitted to two exponential functions. One of the observed pseudo-first-order rate constants, kobs1, exhibits a linear dependence on the hydrogen peroxide concentration with a zero intercept, whereas the other rate constant, kobs2, was independent of the hydrogen peroxide concentration. A mechanistic interpretation is presented.Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2005/1999/99068_s.pdf or from the author.
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    Synthesis of Tumor-Inhibiting Complex Salts Containing the Anion trans-Tetrachlorobis(indazole)ruthenate(III) and Crystal Structure of the Tetraphenylphosphonium Salt (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1551-1555 
    Details
    ISSN: 1434-1948
    Keywords: Ruthenium ; Coordination chemistry ; Paramagnetic complexes ; Magnetic properties ; Ion exchange ; Antitumor agents ; Colon tumors ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Indazolium trans-tetrachlorobis(indazole)ruthenate(III) exhibits excellent results against different tumor models in vitro and in vivo. To improve the water solubility necessary for the introduction of this tumor-inhibiting compound into clinical trials, we synthesized the corresponding sodium salt in a two-step ion exchange via the tetramethylammonium salt. The sodium salt shows a 35-fold higher solubility in water relative to the indazolium salt. We also synthesized the n-butylammonium, n-octylammonium, and tetraphenylphosphonium salts, all of which showed improved solubility in organic solvents. The X-ray crystal structure of the latter could be solved, proving the trans configuration of the complex anion. In spite of the paramagnetic RuIII center an assignement of the coordinated indazole protons could be made with the help of a COSY experiment.
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    (N-lithioamino)diorganophosphanes and Bis(N-Lithioamino)organophosphanes: Synthesis and Structures (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2355-2368 
    Details
    ISSN: 1434-1948
    Keywords: Phosphane complexes ; Lithium ; Aminophosphanes ; Hydrazides ; (N-lithioamino)diorganophosphanes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Butyllithium (nBuLi) deprotonates Ph2P-NHtBu in ether to give (Ph2P-NLitBu)2·OEt2. There is no Li···P interaction in this molecule. Three compounds of the type R′P(NLiR)2 have been obtained by lithiation of R′P(NHR)2, isolated as [BuP(NLitBu)2·OEt2]2, [PhP(NLiPh)2·OEt2]2 and [PhP(NLiPh)2]2. Reaction of nBuLi with MeP(NHiPr)2 in hexane/THF leads to [MeP{N(Li)iPr]2·THF}4 with an asymmetric cluster structure comprising one LiP3, three LiPN2, three LiP2N and one LiN3 cluster units. The molecular structures of these compounds as determined by X-ray structure analysis show that they are best depicted as N-lithioaminophosphanes and not as the isomeric P-lithioiminophosphoranes.
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    Reactivity of Carbonyl-Functionalized Phosphaalkenes RC(O)P=C(NMe2)2 (R = tBu, Ph) towards Electrophiles (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2369-2381 
    Details
    ISSN: 1434-1948
    Keywords: Alkylation ; Carbonyl complexes ; Lewis acids ; Phosphaalkenes ; Protonation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of the carbonyl-functionalized phosphaalkenes RC(O)P=C(NMe2)2 [R = tBu (2a), Ph (2b)] with protic acids and alkylating reagents occurred at the two-coordinate phosphorus atom to give the phosphanyl-substituted carbocations 3a,b and 4a,b. In contrast, treatment with Me3SiOSO2CF3 resulted in attack at the oxygen atom by the silyl group, and the formation of [RC(OSiMe3)=PC(NMe2)2]SO3CF3 (5a,b). Similarly, the Lewis acids B(C6F5)3, Al(tBu)2Cl and AlMe3 were ligated to the oxygen atom of the carbonyl group. Two equivalents of GaMe3 were added to the oxygen and phosphorus atom of the phosphaalkene to yield the thermolabile complexes [RC(OGaMe3)=P(GaMe3)C(NMe2)2] (10a,b). In contrast, one molecule of InMe3 was bound to the phosphorus center of the phosphorus compound. Reaction of the phosphaalkenes with [Ni(CO)4], [Fe2(CO)9] or [{(Z)-cyclooctene}Cr(CO)5] also took place at the pnictogen atom, resulting in complexes of the type [RC(O)P{M(CO)n}C(NMe2)2] (R = tBu, Ph; M = Ni, n = 3; Fe, n = 4; Cr, n = 5). The chemical transformations reported here underline the versatile chemistry of phosphaalkenes and emphasize a relationship between carbonyl-functionalized phosphaalkenes and the well-investigated class of phosphorus ylides. X-ray structures of compounds 6b, 7b*, 10a, 11a and 12a are reported.
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    Synthesis and Structures of (N3)2Ga[(CH2)3NMe2], (N3)Ga[(CH2)3NMe2]2 and (N3)3Ga(NR3) (R = CH3, C2H5) (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2127-2134 
    Details
    ISSN: 1434-1948
    Keywords: Gallium ; Azides ; Chemical vapour deposition ; Gallium nitride ; Single source precursors ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis, properties and X-ray single crystal structure analysis of the intramolecularly adduct-stabilised organogallium bisazide (N3)2Ga[(CH2)3NMe2] (1), the mono azide (N3)Ga[(CH2)3NMe2]2 (2) and the trialkylamine adducts of triazidogallium of the type (N3)3Ga(NR3) (3a-d; R = alkyl) are reported. An unusual isomer 1b of compound 1 is described, which was obtained by slow cooling of the analytically pure neat liquid compound 1 to 0 °C. The new and unusual structure 1b can be regarded as a weak associate of dimers linked together by head-to-tail azide bridges. In contrast, compounds 2 and 3a-b (R = CH3, C2H5) are monomeric in the solid state. The suitability of the volatile compounds 1 and 2 as single source precursors to grow GaN thin films by chemical vapour deposition is compared, showing that preferentially oriented crystalline films can be obtained from compound 2 on sapphire substrates at 600-700 °C in vacuo (0.1 Pa). However the films have a grey rather than a transparent appearance, which is presumably due to N-deficiency owing to the lower N-content of the single molecule precursor 2 relative to 1.
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    Activity of Peroxo and Hydroperoxo Complexes of TiIV in Olefin Epoxidation: A Density Functional Model Study of Energetics and Mechanism (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2135-2145 
    Details
    ISSN: 1434-1948
    Keywords: Density functional calculations ; Epoxidation ; Peroxo complexes ; Titanium ; Transition states ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Epoxidation of olefins by TiIV peroxo and hydroperoxo (alkylperoxo) complexes was investigated using a hybrid DFT method (B3LYP). Reaction energies and activation barriers for direct oxygen transfer to ethylene as a model olefin were computed for various model complexes to compare the epoxidation activity of Ti(η2-O2) and TiOOR (R = H, CH3) moieties. The activity of complexes with a Ti(O2) peroxo group is shown to be essentially quenched when the coordination sphere of the complex is saturated by strongly basic (σ-donor) ligands. In contrast, the activity of a TiOOH functional group depends only weakly on the saturation of the coordination sphere of the Ti center. Substitution of methyl for hydrogen in a TiOOH group is found to slightly increase the activation barrier of epoxidation. The computational results give preference to reaction paths that involve TiOOR species. The factors governing the activity of Ti(O2) and TiOOR groups, in particular the effects of donor ligands, are discussed on the basis of a molecular orbital analysis.
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    Water/Ethanol Displacement Reactions in Vanadyl Phosphate (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2289-2294 
    Details
    ISSN: 1434-1948
    Keywords: Intercalations ; Vanadyl phosphate ; Ethanol ; Hydration ; Kinetics ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The course of the replacement of ethanol by water molecules in the VOPO4·2C2H5OH intercalate, and of water by ethanol in VOPO4·2H2O has been studied by X-ray diffraction and infrared and Raman spectroscopy. Formation of mixed phase VOPO4·C2H5OH·H2O was not observed. The shape of the kinetics curves indicates a transition of at least one reaction zone through the crystal. A delay in formation of the product in comparison with the decrease in the amount of starting material can be explained by the existence of non-diffracting advancing phase boundary. In a VOPO4/ethanol/water system, VOPO4·2C2H5OH is formed as the only product when the system contained more than 96 vol% of ethanol, whereas in the system with less than 94 vol% of ethanol only VOPO4·2H2O is present.
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    The Dramatic Influence of Diamidoamine Ligands on the Structure and Reactivity of Low-Valent Tin and Bismuth Derivatives (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2295-2299 
    Details
    ISSN: 1434-1948
    Keywords: Lewis acids ; Bismuth ; Aluminum ; Phosphorus ; Tin ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dilithium salts of N-methyl-N′,N′′-bis(diisopropyl)- and -(trimethylsilyl)-diethylenetriamine 1a,b react with SnCl2 affording the corresponding stannylenes 2a,b in 60 and 80% yield, respectively. Compound 1b also reacts with BiCl3 to give the bismuth chloride 5 (90% yield). Derivatives 2b and 5 have a symmetrical bicyclic structure and are monomeric both in solution and in the solid state. When 2b is treated with BiCl3 or PCl3, an oxidation reaction leads to the hypercoordinated tin(IV) dichloride 3 (58% yield), or a transmetallation gives rise to the oniophosphane 4 (95% yield), respectively. Transmetalation reactions also occurred when 5 was treated with AlCl3, GaCl3 or SnCl2 affording the corresponding aluminum chloride 6 (81% yield), gallium chloride 7 (38% yield) or tin dichloride 3 (38% yield). The observed reactivity for 2 and 5 is compared to that reported for Veith's stannylene or bismuth chloride.
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    Synthesis, Spectroscopy and Photophysical Properties of Ruthenium Triazole Complexes and Their Application as Dye-Molecules in Regenerative Solar Cells (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2309-2317 
    Details
    ISSN: 1434-1948
    Keywords: Ruthenium ; Triazole ; Titanium ; Electron Transfer ; Sensitizers ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The complexes [Ru(dcb)2(L)] {L = 3-(2-hydroxyphenyl)-5-(pyridin-2-yl)-1,2,4-triazole (2-ppt), 3-(4-hydroxyphenyl)-5-(pyridin-2-yl)-1,2,4-triazole (4-ppt), 3,5-bis(pyrazin-2-yl)-1,2,4-triazole (bpzt), 3-(2-hydroxyphenyl)-5-(pyrazin-2-yl)-1,2,4-triazole (2-ppzt) and dcb = 4,4′-(CO2H)2-2,2′-bipyridine} have been synthesized, spectroscopically characterized and anchored to nanocrystalline TiO2 electrodes for the conversion of light into electricity in regenerative solar cells. The different efficiencies observed have been rationalized on the basis of an analytical expression relating the incident photon-to-current conversion efficiency (IPCE) to the kinetic parameters of the relevant electron transfer processes involved in the solar cell.
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    Directed Syntheses of New Quaternary Niobium Oxysulfides: Crystal Structures and Properties of K4Nb2S10O and Rb4Nb2S10O Compared to K4Nb2S11 (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1295-1299 
    Details
    ISSN: 1434-1948
    Keywords: Solid-state chemistry ; Structure elucidation ; Reactive flux syntheses ; Oxysulfides ; Niobium chalcogenides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The new compounds K4Nb2S10O and Rb4Nb2S10O have been synthesized by the reaction of potassium or rubidium alkaline polychalcogenides with NbO2, Nb2O5, or mixtures of Nb and NbO. Their structures consist of discrete [Nb2Q11]4- anions (Q = O, S) built up of two face-sharing pentagonal bipyramids, which are connected via the alkali metal cations.
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    Pyrazolato Metal Complexes - Synthesis, Characterization, and X-ray Crystal Structures of Heterotrimetallic Re-M2 Derivatives (M = Cu, Ag, Au) (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1301-1307 
    Details
    ISSN: 1434-1948
    Keywords: Pyrazolato ligands ; Rhenium ; Group-11 metals ; Heterometallic complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By treating [(CO)3Re(Hpz)2(pz)] (Hpz = pyrazole) with [Cu(CH3CN)4]BF4, AgNO3, or [Au(tht)Cl] (tht = tetrahydrothiophene) in acetonitrile in the presence of Et3N, the corresponding trinuclear complexes {(CO)3Re(pz)3[M(CH3CN)]2} (1a-c) have been obtained. Treatment of complexes 1a-c with cyclohexyl isocyanide (c-C6H11NC) afforded the derivatives {(CO)3Re(pz)3[M(c-C6H11NC)]2} (2a-c). Complexes 2a-c have been characterized in solution by 1H-NMR spectroscopy and in the solid state by single-crystal X-ray diffraction analysis.
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    Synthesis and Investigations on Nitrido(phthalocyaninato)rhenium Complexes (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1309-1313 
    Details
    ISSN: 1434-1948
    Keywords: Phthalocyanines ; Rhenium ; Nitrido(octa-n-alkylphthalocyaninato)rhenium compounds ; Nucleophilic additions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of nitrido(tetra-tert-butylphthalocyaninato)rhenium (1) with boron tribromide leading to (tBu4Pc)ReNBBr3 (4) and with acetone to give the imido complex (tBu4Pc)Re[NC(CH3)2CH2C(O)CH3]OH (2b) and its μ-oxo dimer 3 are reported. Starting from the corresponding 4,5-di-n-alkylphthalonitriles and ammonium perrhenate four soluble nitrido(octa-n-alkylphthalocyaninato)rhenium complexes 5-8 were synthesized. Nitrido(octa-n-pentylphthalocyaninato)rhenium (6) was treated with boron tribromide to afford [(C5H11)8Pc]ReNBBr3 (9).
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    Di- and Tripalladium(II) and -platinum(II) Complexes Containing 7-Amino-1,8-naphthyridin-2-one as a Bridging Ligand - Oxidation of a [Pt3]6+ Core to [Pt3]8+ (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1325-1333 
    Details
    ISSN: 1434-1948
    Keywords: Platinum ; Palladium ; Platinum blues ; Naphthyridine complexes ; Trinuclear complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: All three dinuclear complexes [Pd2(donp)2(bpy)2] (1) (H2donp = 1,8-naphthyridin-2,7-dione), [Pd2(H2nonp)2(bpy)2](ClO4)2 (2), and [Pt2(H2nonp)2(bpy)2](PF6)2 (3) (H3nonp = 7-amino-1,8-naphthyridin-2-one) exhibit the μ-1ĸN1:2ĸN8 bridging mode for their head/tail orientated naphthyridine ligands. Whereas 1 and 3 may be prepared by direct reaction of the dinucleating ligand with [MCl2(bpy)], formation of competing tripalladium(II) complexes must be avoided for 2 by employment of the precursor H2acnonp (7-acetamido-1,8-naphthyridin-2-one), which affords [H2nonp]- on cleavage of its original acetyl group. A mixture of the head/tail (4a) and head/head (4b) isomers of [Pd3(Hnonp)2(bpy)3](ClO4)2 is obtained when H3nonp is treated with [PdCl2(bpy)] and LiOH at room temperature for 2 d, followed by precipitation with LiClO4. Contrastingly exclusive formation of 4a is observed upon refluxing this reaction mixture for 3 d in aqueous solution. The [Hnonp]2- ligands exhibit a μ3-1ĸN1:2ĸN8:3ĸN7 bridging mode that leads to short Pd···Pd interactions of 2.781(2) and 2.775(2) Å. Similar metal-metal distances of 2.771(3) and 2.816(3) Å are observed in head/head-[Pt3(acnonp)(Hnonp)(bpy)3]Cl2 (5). An in situ 2e--oxidation (Ag+/Ag) of the [Pt3]6+ core in triplatinum(II) species such as 5 formed by the reaction of [PtCl2(bpy)] with H2acnonp allows the isolation of diamagnetic dark-brown head/head-[Pt3(Hnonp)2(NO3)(bpy)3](ClO4)2(NO3) (6) with an average oxidation state of Pt (2.67+). The Pt-Pt distances of 2.723(2) and 2.670(2) Å are markedly shorter than in 5.
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    Synthesis and Single-Crystal X-ray Diffraction Studies on New Methylindium(III) Alkoxides (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1343-1350 
    Details
    ISSN: 1434-1948
    Keywords: Indium ; O ligands ; N ligands ; C ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New heteroleptic indium compounds have been synthesized starting from indium(III) halides and hexamethyldisilazyllithium to form MeXInN(SiMe3)2 [X = Cl (1), Br (2)], and then subsequent alcoholysis to afford the molecules [ClMeIn(OtBu)]2 (3), [BrMeIn(OtBu)]2 (4), {ClMeIn[O(C6H4)OMe]}2 (5), {[(SiMe3)2N]MeIn(OtBu)}2 (6) and [MeIn(OtBu)2]2 (7). The molecular structures of molecules 3-7 have been obtained by single crystal X-ray diffraction studies. The structures of the compounds 3-7 are almost identical: 3-5 crystallize in the monoclinic crystal system with two dimeric molecules per unit cell in the space group P21/c, 6 crystallizes in the monoclinic space group C2/c with four molecules per unit cell, and compound 7 crystallizes in the triclinic crystal system with one dimeric molecule per unit cell in the space group P-1. The central centrosymmetric In2O2 ring, common to all the compounds, is achieved by two bridging oxygen atoms. Due to the additional coordination by an oxygen atom of the methoxy group, the coordination number of the metal center rises from 4 to “4+1” if the OtBu ligand (compounds 3, 4, 6, and 7) is exchanged for a methoxyphenol ligand (compound 5). In addition to the In2O2 ring the compound 5 possesses two annealed five-membered InO2C2 rings. The common indium methyl group of all compounds, which is transfered by an original route from the silicon to the indium atom, is used to compare structural and spectroscopic properties of the molecules, as there is a correlation between the In-C bond length and the chemical shift of the methyl group which depends on the ligand system used.
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    Synthesis, Chemistry, and Characterization of Perfluoroaromatic Selenium Derivatives (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1359-1366 
    Details
    ISSN: 1434-1948
    Keywords: Selenium ; Fluorine ; Multinuclear NMR ; Raman spectroscopy ; X-ray crystallography ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of perfluoroaryllithium RC6F4Li, where R = F or 4-CF3C6F4O, respectively, with selenium gives the known diselanes (RC6F4Se)2 (1a, 1b). Redox reactions of 1 with hydrogen peroxide result in the formation of the seleninic acids RC6F4SeOOH which crystallize as hydrates (2a, 2b); with mercury give the bis(arylseleno)mercuries (RC6F4Se)2Hg (3a, 3b); with sulfuryl chloride or bromine give the selenenyl chlorides (4a, 4b) or selenenyl bromides (5a, 5b). Selenenyl chlorides (4a, 4b) react with a variety of trimethylsilyl reagents Me3SiX (X = Br, CN, NMe2, NEt2) to form 5a, 5b; selenocyanates RC6F4SeCN (6a, 6b); selenenyl amides RC6F4SeNMe2 (7a, 7b) and RC6F4SeNEt2 (8a, 8b). A new synthetic route to diorgano selanes is developed by reaction of 4a, 4b with perfluoroaryllithium to give the symmetric (RC6F4)2Se (9a, 9b). All derivatives are thoroughly characterized and in addition the molecular structures of 2a, 6a, and 9a are established by X-ray crystallography.
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    Synthesis, Mesomorphism, and Spectroscopic Characterization of Bis[4-(n-alkoxy)-5-(p-n-tetradecylphenylazo)]-Substituted (N,N′-Salicylidenediaminato)nickel(II) Complexes (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1367-1372 
    Details
    ISSN: 1434-1948
    Keywords: Metallomesogens ; Nickel ; Salicylidenediamines ; Azo compounds ; (E)/(Z) photoisomerization ; Isomerizations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The bis[4-(n-CmH2m+1O)-5-(p-C14H29C6H4N=N)]-substituted N,N′-salicylidenediamines H2[LN(m,14)] (N = 1: 1,2-diaminoethane; N = 2: 1,3-diaminopropane; N = 3: 1,3-diamino-2,2-dimethylpropane; m = 6 or 18) have been synthesized. Both the N = 2 and 3 series of compounds display a smectic C (SmC) mesophase, with clearing points well below 100 °C. By treating the H2[LN(m,14)] ligands with an NiII salt, liquid crystalline mononuclear complexes with “unconventional” (lateral-tailed) molecular shape form. These Ni[LN(m,14)] complexes, showing nematic and smectic disordered phases, are stable over a quite large temperature range and have been characterized by different spectroscopic techniques. The newly synthesized mesogens exhibit lower transition temperatures and higher thermal stability than homologous complexes Ni[LN(14)] with a “conventional” rod-like molecular geometry.
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    Mechanism of the Catalytic Oxidation of Tertiary Alcohols by the Water-Soluble Mn-TMPyP/KHSO5 System: β-Fragmentation versus O-Neophyl Rearrangement (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1467-1477 
    Details
    ISSN: 1434-1948
    Keywords: Oxidations ; Tertiary alcohol ; Porphyrins ; Neophyl rearrangement ; Cleavage reactions ; β-Scission ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxidation of 4-(1-hydroxy-1-phenylethyl)benzoic acid HPEBA with a water-soluble metalloporphyrin as catalyst and KHSO5 as oxygen atom donor gives the major products, acetophenone AC and acetylbenzoic acid ABA, by a Caliph-CAr bond cleavage, but a minor product, benzoyloxybenzoic acid BOBA, requires the insertion of an oxygen atom to form the ester. This compound becomes the main oxidation product on increasing the amount of acetonitrile in the reaction medium, and its formation is oxygen-dependent. The conversion is drastically lowered by using D2O instead of H2O, suggesting that an alkoxyl radical is formed in the rate-determining step. Labeling experiments using 18O2 or H218O under different reaction conditions show that the carbonyl oxygen atoms of AC and ABA originate either from substrate, water or dioxygen. However, the carbonyl oxygen atom in the ester group of BOBA originates from dioxygen while the other oxygen atom of the ester remains unlabeled. These results can be explained by an O-neophyl rearrangement of the initial alkoxyl radical to afford a carbon-based radical which then reacts with dioxygen or MnIV-OH/water. In a competitive reaction pathway, direct β-scission of the alkoxyl radical leads to unlabeled products. The oxidation of other tertiary diaryl alcohols is also discussed.
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    Histidine-Containing Bisperoxovanadium(V) Compounds: Insight Into the Solution Structure by an ESI-MS and 51V-NMR Comparative Study (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1489-1495 
    Details
    ISSN: 1434-1948
    Keywords: Peroxo complexes ; Vanadium ; Mass spectrometry ; 51V-NMR spectroscopy ; Vanadium dependent bromoperoxidases ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ESI mass spectrometry and 51V-NMR spectroscopy have been used to study the reactions occurring between bisperoxo vanadates and a number of histidine and histidine-like ligands, in aqueous alcoholic solutions. Coordination of one and two molecules of ligand is observed with all the compounds investigated affording [VO5L]- and [VO52L]-, respectively. Characterization of these species has been achieved by MSn experiments, which have allowed specific fragmentations of the peroxidic moiety to be distinguished. In particular, with [VO52L]-, two distinct modes of decomposition were observed, depending on the presence in the ligand of a free carboxylic function. - Possible biochemical implications related to vanadium haloperoxidase enzymes are discussed.
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    Tungsten Carbonyl Complexes of 1H-Diphosphirenes and Diphosphirenylium Salts (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1479-1488 
    Details
    ISSN: 1434-1948
    Keywords: Phosphorus heterocycles ; Cations ; Tungsten complexes ; Coordination modes ; Phosphaalkenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1,1,3-tris(diisopropylamino)diphosphirenium salt 1 reacts with lithium aluminium hydride leading to the P-hydrogeno-C-phosphinophosphaalkenes 2, which on treatment with a catalytic amount of BF3·OEt2 afford the 1,3-bis(diisopropylamino)-1H-diphosphirene 3. The corresponding η1-coordinated 1H-diphosphirene 6 can be prepared by treatment of 2 or 3 with one equivalent of [W(CO)5(thf)]. Alternatively, the diphosphirenium salt 1 reacts with an excess of [W(CO)5(thf)], affording the corresponding η1-coordinated diphosphirenium salt complex 4, which is converted into the P-hydrogenophosphaalkene complex 5 with lithium aluminium hydride. The dinuclear tungsten complexes 7 and 8 are obtained by treatment of the free 1H-diphosphirene 3 with two equivalents of [W(CO)5(thf)] or one equivalent of [W(CO)4(thf)2], respectively. Compound 6 reacts with two equivalents of hydrogen chloride, giving the 1-chloro-3-diisopropylamino-1H-diphosphirene 9, which can be subsequently converted into the 1-diisopropylamino-, 1-azido, or 1-phenyl-3-diisopropylamino-1H-diphosphirenes 6, 10 and 11 by nucleophilic substitution with diisopropylamine, azidotrimethylsilane or sodium tetraphenylborate, respectively. The [η2-(3-diisopropylaminodiphosphirenylium salt)·W(CO)5] complexes 12a-c can be prepared by reaction of 9 with silver trifluoromethanesulfonate, aluminium or gallium trichloride or, alternatively, by treatment of 6 with two equivalents of trifluoromethanesulfonic acid. Reaction of 12a with diisopropylamine, water, bis(triphenylphosphoranylidene)ammonium chloride or tetrabutylammonium fluoride gives the corresponding 1H-diphosphirene complexes 6, 13, 9, or 14, respectively. Compound 12a also reacts with one or two equivalents of [W(CO)5(thf)], leading to the di- and tri-nuclear complexes 15and 16, respectively.
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    Syntheses and Characterization of New Tertiary Phosphane Ligands Prepared from p-Anisyl- and p-Thioanisyldichlorophosphanes (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1253-1258 
    Details
    ISSN: 1434-1948
    Keywords: Phosphane ligands ; 31P-NMR spectrometry ; Substituent increments ; Electronic and steric properties ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The syntheses and spectroscopic parameters of the new tertiary phosphane ligands (p-MeOC6H4)(o-MeOC6H4)2P (1), (p-MeOC6H4)(o-MeSC6H4)2P (2), (p-MeSC6H4)(o-MeSC6H4)2P (3), (p-MeSC6H4)(o-MeOC6H4)2P (4), (p-MeOC6H4)(o-NC5H4)2P (5), and (p-MeSC6H4)(o-NC5H4)2P (6) are reported. Single-crystal X-ray structures of all the compounds (1-6) have been determined. The dependence of the 31P-NMR chemical shifts on the substituent groups of the phosphanes is discussed.
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    Solvates of Sodium Bis(borane)dimethylamide (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1373-1379 
    Details
    ISSN: 1434-1948
    Keywords: Sodium bis(borane)dimethylamide solvates ; X-ray structure ; Reduction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of sodium metal with dimethylamine-borane in THF yields Na[(H3B)2NMe2] (1) which can be isolated as {Na[(H3B)2NMe2]}5·THF or as Na[(H3B)2NMe2]·15-crown-5 (2) and Na[(H3B)2NMe2]·benzo-15-crown-5 (3) after addition of the appropriate crown ether to the THF solution of 1. Reaction of 1 with ZrCl4 yields Me2HN-BH2-NMe2-BH3 (4), the structure of which has been determined. In THF solution, 1 reduces aldehydes, ketones, acyl chlorides, and esters to the corresponding alcohols. It also reacts slowly with nitriles and allylbenzene. Compound (1)5·THF crystallizes in an extended three-dimensional lattice, in which the Na atoms are coordinated by 6-9 hydridic H atoms, while 3 is a molecular compound in the solid state. Only one hydrogen atom of each BH3 group coordinates to the sodium center. On the other hand, 4 forms dimeric associates in the solid state through N-H···H-B interactions.
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    Halogenation of Alkenes in Five-Coordinate Platinum(II) Complexes - A Route to Stable (β-Haloalkyl)platinum(IV) Species (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1351-1358 
    Details
    ISSN: 1434-1948
    Keywords: Haloalkyl complexes ; Five-coordinate platinum complexes ; Alkene complexes ; Olefin halogenation ; Oxidative addition ; Platinum ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Five-coordinate complexes [PtX2(olefin)(2,9-Me2-phen)] (1; 2,9-Me2-phen = 2,9-dimethyl-1,10-phenanthroline; olefin = ethene denoted by a, propene by b, 1-butene by c; × = Cl denoted by x, Br by y) undergo photoactivated reactions with Cl2 and Br2 to give the (β-haloalkyl)platinum(IV) complexes [Pt(CH2CHRX)(2,9-Me2-phen)X3] (2). Bromination of the chloro species 1ax leads to the formation of the PtIV species 2axy containing the bromide, the bromoalkyl, and the phenanthroline ligands in the equatorial plane and two chloride ions in axial positions. The iodo complexes 1(a-c)z are not oxidized by iodine even under UV irradiation but react readily with Cl2 or Br2 to give 2(a-c)x and 2(a-c)y. The structure of 2ay, the first structurally characterized (β-haloalkyl)platinum complex, has been determined by X-ray diffraction methods. The stereochemistry of the (β-haloalkyl)platinum(IV) complexes is in accord with a simultaneous addition of two halogen atoms to the coordinated olefin and to the metal center.
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    Intermediates and Products of the Hexachlorodisilane Cleavage of Group 14 Element Phosphanes and Amines - Molecular Structure of Di-tert-butyl(trichlorosilyl)phosphane in the Gas Phase Determined by Electron Diffraction and ab Initio Calculations (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1381-1392 
    Details
    ISSN: 1434-1948
    Keywords: Phosphanes ; Disilanes ; Disilanylamines ; Germanes ; Stannanes ; Stannanes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of dialkyl(trimethylsilyl)phosphanes RR′PSiMe3 (1:R, R′ = tBu; 3: R, R′ = iPr; 5: R = iPr, R′ = tBu) with Si2Cl6 provide stable trichlorosilylphosphanes RR′PSiCl3 (2, 4, 6); the reactions of silyl- and stannylamines of iPr2NMMe3 (M = Si: 11; M = Sn: 12) with Si2Cl6, however, provide the stable pentachlorodisilanylamine iPr2NSi2Cl5 (13). Heating of 1 with the technical mixture Me2(Cl)SiSiCl2Me/(MeCl2Si)2 yields the stable silylphosphane tBu2PSiMe2Cl (8) and the disilanylphosphane tBu2PSi(Me)(Cl)Si(Me)Cl2 (9). Methylation of 9 with MeLi gave tBu2PSi2Me510, which was isolated in a pure state. Reactions of tBu(iPr)PSiMe3 (5) and of organometal phosphanes tBu(iPr)PMR3 (14: M = Ge, R = Me; 17a-c: M = Sn; R = Me, Et, nBu) with Si2Cl6 were monitored by 31P, 29Si, and 119Sn NMR. - In the first step of these reactions, new tBu(iPr)PSi2Cl5 (7) is formed. 7 is accompanied by increasing amounts of tBu(iPr)PSiCl3 (6) and Me3GeSiCl3 (15)/(Me3Ge)2Si(SiCl3)2 (16) or traces of compounds R3SnSiCl3 (19a-c) that decompose providing (R3Sn)2Si(SiCl3)2 (18a-c) and nBu3SnSi(SiCl3)3 (20c). Subsequently, compounds 19a-c decompose providing increasing amounts of 18a-c. Stannylphosphane 17bis also cleaved by SiCl4 leading to 6 with liberation of Et3SnCl, whereas 17bis formedfrom the reaction of 5 with Et3SnCl under liberation of Me3SiCl. The suggestion of an extra stabilisation of P-Si bonds of trichlorosilylphosphanes was subjected to direct evidence through the structure determination of the trichlorosilylphosphane tBu2PSiCl3 (2) in the gas phase by electron diffraction. This crowded molecule has a “normal” P-Si bond length of 225.0(12) pm; its C1 symmetric conformation with both tBu groups and the SiCl3 group twisted about 17° from the perfectly staggered positions, and with each of the three groups tilted about 6° away from each other, allows to reduce steric strain.
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    Self-Assembly, Structure, and Physical Properties of Tetranuclear ZnII and CoII Complexes of [2 × 2] Grid-Type (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1421-1428 
    Details
    ISSN: 1434-1948
    Keywords: Grid complexes ; Self-assembly ; Co ; Zn ; Coordination chemistry ; Bis(tridentate) ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The tretrametallic [2 × 2] grid-type complexes 1-4 are formed by self-assembly of the bis(tridentate) ligands 5 and 6 with ZnII and CoII cations. They have been characterized by spectroscopic studies in solution as well as by crystal structure determination. The substituents in the central pyrimidine ring play an important role in terms of geometry and physical properties of the complexes. They induce an orthogonal orientation of the ligand in the complexes which is critical for the formation of ordered monolayers and extended self-organized arrays of grids. The physical properties of the complexes such as metal-metal interaction and π-π* stacking between the ligands may be modulated by changing these substituents.
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    A Tetranuclear Platinum Compound Designed to Overcome Cisplatin Resistance (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1429-1433 
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    ISSN: 1434-1948
    Keywords: Antitumor drugs ; Platinum ; DNA ; Dendrimers ; L1210 Mouse leukemia ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and characterisation of the first generation of a poly(propyleneimine) dendrimer DAB(PA)4, substituted with four trans-diamminechloroplatinum moieties is reported. The compound DAB(PA-tPt-Cl)4 was designed to overcome two problems often associated with cisplatin resistance in cancer cells: (i) deactivation of the platinum species by intracellular thiolates and (ii) improved repair of crosslinks with DNA. The four-armed molecule can be expected to form crosslinks with DNA that are very different from the adducts formed by cisplatin. Also, the tetranuclear compound has four leaving groups, while cisplatin has only two. Therefore, DAB(PA-tPt-Cl)4 would be less susceptible towards inactivation by reaction with intracellular thiolates. A reaction with an excess of the model nucleobase guanosine 5′-monophosphate (GMP) confirmed that the tetranuclear compound is capable of binding a maximum of four nucleobases. Therefore, the inactivation of one or two arms would still leave the molecule with enough reactivity to form crosslinks with DNA. Cytotoxicity tests were performed on two mouse leukemia L1210 cell lines, both sensitive and resistant towards cisplatin, and in seven human tumor cell lines. In all cell lines, the tetranuclear compound showed a low cytotoxicity. It is suggested that the low activity is related to the structure of the compound. Probably the high charge (+6) at physiological pH and its branched structure hamper the molecule in crossing the cell membranes.
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    Formation of the [(s-trans-η4-Butadiene)TaCp*Cp]+ Cation and Its Reaction with Organic Carbonyl Derivatives (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1453-1459 
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    ISSN: 1434-1948
    Keywords: Group-5 bent metallocene cation complexes ; (Butadiene)tantalocene cation ; (s-trans-η4-Butadiene)metal complex ; Ethene polymerization ; Metallocenes ; Homogeneous catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (Butadiene)TaCp*Cl2 (6) was treated with CpNa to yield (η2-butadiene)TaCp*CpCl (7). Subsequent reaction with [Cp2ZrCH3+][CH3B(C6F5)3-] resulted in transfer of the chloride ligand from tantalum to zirconium with formation of the [(s-trans-η4-butadiene)TaCp*Cp]+ cation [8, with CH3B(C6F5)3- anion]. Complex 8 was characterized spectroscopically and by an X-ray crystal structure analysis. The group-5 [(s-trans-η4-C4H6)TaCp*Cp]+ bent metallocene cation complex 8 reacts with ketones (acetone, adamantanone) to yield the corresponding seven-membered 2-tantalatetrahydrooxepine cation complexes (9, 10). 1-Cyanoadamantane reacts with 8 to yield the 2-tantala-3,6-dihydro-2H-azepine cation system 11. Activation of 8 with methylalumoxane gives an active ethene polymerization catalyst.
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    New Inorganic Metallacycles and the First Six-Membered Covalent “True” Heterocycle - Oxidation of RC(E)NHPPh2 (E = O or S; R = H2N, Ph, or Py) with O, S, or Se to Give RC(E)NHP(E′)Ph2 (E′ = O, S, Se) and Their Coordination Chemistry (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1445-1452 
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    ISSN: 1434-1948
    Keywords: Metallacycles ; Solid-state structures ; Heterocycles ; Oxidations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Direct oxidation of PhC(O)NHPPh2, H2NC(S)NHPPh2, (C5H4N)C(S)NHPPh2 with O2, S8, or Se gives [PhC(O)NHP(O)Ph2] (1), [H2NC(S)NHP(S)Ph2] (2), [H2NC(O)NHP-(S)Ph2] (3), [PhC(O)NHP(S)Ph2] (4), [(C5H4N)C(S)NHP(S)Ph2] (5), and [H2NC(S)NHP(Se)Ph2] (6). Deprotonation of 1, 2, 4-6 with potassium tert-butoxide gives K[PhC(O)NP(O)Ph2] (7), K[H2NC(S)NP(S)Ph2] (8), K[PhC(O)NP(S)Ph2] (9), K[(C5H4N)C(S)NP(S)Ph2] (10), and K[H2NC(S)NP(Se)Ph2] (11). Reaction of 4with KOBu and [Cu(Ph3P)2][NO3] gives [Cu(Ph3P)(PhC(O)NP(S)Ph2)] (12) which is the first crystallographically characterised example of a non-ionic six-membered “true” heterocycle (i.e. a ring in which every heterocatom is different). 9 and 10 were treated with [PdCl2(COD)] to give [Pd{PhC(O)NP(S)Ph2}2] (13) and [Pd{(C5H4N)C(O)NP(S)Ph2}2] (14), respectively The anion of 8 coordinates to zinc forming [Zn{H2NC(S)NP(S)Ph2}2] (15). Treatment of 2 or 8 with [PtCl2(COD)] gives [Pt{H2NC(S)NP(S)Ph2}{H2NC(S)NHP(S)Ph2}]+Cl- (16) and [Pt{H2NC(S)NP(S)Ph2}2] (17), respectively. The X-ray structures of 12, 15-17are reported.
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    Boryl and Bridged Borylene Complexes of Iron and Ruthenium (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1523-1529 
    Details
    ISSN: 1434-1948
    Keywords: Boron ; Iron ; Ruthenium ; Boryl Complexes ; Borylene Complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactivity of aminodihaloboranes R2NBX2 (R = Me, SiMe3; × = Cl, Br) towards transition metal complexes of the type Na[(η5-C5R′5)M(CO)2)] (M = Fe, Ru; R′ = H, Me) was investigated. In the case of Me2NBBr2 and M = Fe the borylcomplexes [(η5-C5R′5)(CO)2Fe{BBr(NMe2)}] (C5R′5 = C5H59a; C5R′5 = C5H4Me 9b; C5R′5 = C5Me510) were obtained. The compounds 9aand 9bwere formed together with the corresponding bridged borylene complexes [μ-BNMe2(μ-CO){(η5-C5R′5)Fe(CO)}2] (C5R′5 = C5H511a; C5R′5 = C5H4Me 11b) in a 1:1 ratio, the latter, however, could be isolated from these mixtures as pure materials. In addition the novel boryl and borylene ruthenium complexes [(η5-C5H5)(CO)2Ru{BX(NMe2)}] (X = Cl 12a; × = Br 12b), [(η5-C5H5)(CO)2Ru{BCl{NSiMe3{BClN(SiMe3)2}}}] (13) and [μ-BN(SiMe3)2(μ-CO){(η5-C5H5)Ru(CO)}2] (14) were obtained by similar methods. All compounds were characterized by multinuclear NMR and IR spectroscopy. The structure of 13 in the solid state was determined by a single-crystal X-ray diffraction study.
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    The Detection of O=SiCl2 as an Intermediate During the Combustion Process of SiCl4 with O2 (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1531-1535 
    Details
    ISSN: 1434-1948
    Keywords: SiCl4 Combustion ; OSiCl2 ; Matrix isolation ; Thermodynamic data ; DFT calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: During the technical important combustion of SiCl4 with oxygen [SiCl4(g) + O2(g) = SiO2(s) + 2·Cl2(g)] many intermediates have been detected in the past. However, the presence of the primary species O=SiCl2 has been discussed controversially until today. With the help of matrix isolation technique we have now been successful to monitor O=SiCl2 via its IR spectrum. With the help of quantum chemical calculations the thermodynamic data have been calculated first. On this basis it was possible to find the optimal conditions to trap OSiCl2 from the high-temperature equilibrium. Furthermore it could be shown via IR spectroscopy and quantum chemical calculations, that the radical OSiCl does not play a significant role within this combustion process.
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    Crystal Structure, Infrared, and Polarized Raman Spectra of K3Sm(PO4)2 (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1545-1550 
    Details
    ISSN: 1434-1948
    Keywords: Phosphates ; Structure ; IR spectroscopy ; Raman spectroscopy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The low-temperature form of K3Sm(PO4)2 crystallizes in the monoclinic system [a = 7.4347(5) Å, b = 5.6270(5) Å, c = 9.4919(5) Å, β = 90.870(6)°, Z = 2, space group P21/m]. The structure has been determined using 1263 independent reflections (R = 0.045, Rw = 0.11) and is found to be of the glaserite type. The Raman and infrared spectra have been investigated: they are consistent with the proposed space group and an assignment of the observed frequencies is given.
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    On the Influence of the Bite Angle of Bidentate Phosphane Ligands on theRegioselectivity in Allylic Alkylation (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1237-1241 
    Details
    ISSN: 1434-1948
    Keywords: Palladium ; Phosphane ligands ; Bite angle ; Allylic alkylation ; Molecular modelling ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The natural bite angle of bidentate phosphane ligands influences the isomer distribution (syn and anti) in (1-methylallyl)(bisphosphane)Pd OTf complexes. It was found (31P- and 1H-NMR studies) that the syn/anti ratio changes from 12 (dppp) to 1.3 (sixantphos). Molecular orbital calculations [PM3(tm) level] indicate that for ligands inducing a large bite angle, the phenyl rings of the ligand embrace the allyl moiety, thus influencing the syn/anti ratio. This bite-angle effect on the syn/anti ratio is transferred to the regioselectivity in stoichiometric allylic alkylation. Ligands inducing large bite angles direct the regioselectivity towards the formation of the branched product 2. Catalytic alkylation of (E)-2-butenyl acetate showed that for ligands with a small bite angle the regioselectivity of the catalytic and stoichiometric alkylation are in good agreement. This correspondence is worse for ligands with a larger bite angle, which is rationalised in terms of the relative rates of syn/anti isomerisation and alkylation. The ligand with the largest bite angle (sixantphos) gives the most active catalytic species.
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    Linear Five-Centred Chromium Multiple Bonds Bridged by Four tpda2- Ligands [tpda2- = tripyridyldiamido dianion] - Synthesis and Structural Studies (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1243-1251 
    Details
    ISSN: 1434-1948
    Keywords: Metal string complexes ; Multicentered metal-metal multiple bond ; Quadruple bonds ; Metal-metal interactions ; Chromium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The linear pentanuclear chromium complexes [CrII5(μ5-tpda)4Cl2] (1), [CrII5(μ5-tpda)4(NCS)2] (2), [CrIIICrII4(μ5-tpda)4F2](BF4) (3), and [CrIIICrII4(μ5-tpda)4F(OTf)](OTf) (4), with four all-syn tri(α-pyridyl)diamido dianion (tpda2-) ligands, have been prepared and structurally characterized. Compounds 1 and 2 possess a delocalized Cr(II)-Cr(II)-Cr(II)-Cr(II)-Cr(II) five-centred metal-metal bond of order 1.5. In both 1 and 2 two values for CrII-CrII bond lengths are found both; the outer ones connected with axial ligands are 2.284(1) and 2.285(2) Å, and the inner ones are 2.2405(8) and 2.246(1) Å, for 1 and 2, respectively. When compound 1 reacts with 2 equiv. of AgBF4 or Ag(OTf), a oxidation reaction takes place and one of the terminal chromium(II) ions is oxidized to produce [CrIIICrII4(μ5-tpda)4F2]BF4 (3) or [CrIIICrII4(μ5-tpda)4F(OTf)](OTf) (4). Two short Cr-Cr distances [1.969(2) and 2.138(2) Å for 3, 1.846(1) and 1.922(1) Å for 4] are found, with the presence of two quadruple bonds among four adjacent CrII ions. The fifth CrIII ion, which is separated from the neighboring CrII ion by 2.487(2) Å for 3 and 2.610(1) Å for 4, is simply a square pyramidal unit with no metal-metal bonding interaction.
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    Formation of Calcium-Carbon Bonds From a Lewis Acid-Base Reaction of Calcium Bis[bis(trimethylsilyl)amide] and Tris(trimethylsilylmethyl)alane (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2209-2214 
    Details
    ISSN: 1434-1948
    Keywords: Aluminium ; Amides ; Calcium ; Metallacycles ; Phosphorus ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of calcium bis[bis(trimethylsilyl)amide] with two equivalents of tris(trimethylsilylmethyl)alane yields (Me3SiCH2)2Al-N(SiMe3)2 (1) and the dimer [(Me3Si)2N-Ca(μ-CH2SiMe3)2Al(CH2SiMe3)2]2 (2). The five-coordinate bridging carbon atoms show Ca-C bond lengths of 264 and 268 pm. A similar reaction with calcium bis[bis(trimethylsilyl)phosphanide] gives the dimer [(Me3SiCH2)2Al-P(SiMe3)2]2 (3) with crystallographic C2 symmetry. A calcium-containing species is not isolable, however, in the presence of DME - ether cleavage reactions and the formation of the centrosymmetric dimer [(Me3SiCH2)2Al-OCH2CH2OMe]2 (4) are observed. The central moiety is an Al2O2 cycle with fivefold coordinated aluminium centers.
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    Magnesiation of Triisopropylsilylphosphane: Synthesis and Structures of New Mg2nP2m Polyhedra (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2215-2220 
    Details
    ISSN: 1434-1948
    Keywords: Magnesium ; Metalation ; Phosphorus ; Polyhedra ; X-ray structures ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The magnesiation of triisopropylsilylphosphane with dibutylmagnesium in toluene yields the octanuclear complex [Mg8(PSiiPr3)6{P(H)SiiPr3}4] (1) which consists of MgPSiiPr3 units forming a hexagonal Mg6P6 prism, with two opposite Mg2P2 moieties capped by additional Mg[P(H)SiiPr3]2 groups. If a small amount of THF is present during the metalation reaction [(THF)4Mg6(PSiiPr3)6] (2) also containing a hexagonal Mg6P6 prism can be isolated. The magnesiation of H2P-SiiPr3 in tetrahydrofuran leads to the formation of the tetrameric complex [(THF)MgPSiiPr3]4(3) with a slightly distorted Mg4P4 cubane-like structure.The structures depend strongly on the steric strain caused by the trialkylsilyl substituents and the neutral coligands at the magnesium center. The highest steric strain, which is induced by coordination to every magnesium atom, leads to the smallest MgnPn polyhedron - the central Mg4P4 heterocubane moiety. In compounds 1 and 2 the hexagonal Mg6P6 prism is formed, however, with reduced steric strain as observed for 2 where the Mg-P bond lengths become more similar.
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    Synthesis, X-ray Crystal Structures and Reactivity Towards Alkynes of Gold(I)-Phosphinine Complexes (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2233-2241 
    Details
    ISSN: 1434-1948
    Keywords: Phosphorus ; Heterocycles ; Phosphinines ; Gold ; Cycloadditions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coordination behaviour of 2,6-disilyl-substituted phosphinines towards gold(I) has been examined. The reaction of the bis(trimethylsilyl)phosphinine 1 with [AuCl(SMe2)] gives the corresponding AuCl derivative 2. X-ray crystal structure analysis reveals that the aromaticity of the phosphinine ring is slightly reduced as a result of the poor π-back bonding ability of the AuCl fragment. The same phenomenon is observed in the cationic complex [Au(1)2][GaCl4] (3) which was readily prepared by reaction of two equivalents of 1 with [AuCl(SMe2)] followed by treatment with GaCl3 at low temperature. Reaction of 2,6-bis(phenylethynyldimethylsilyl)phosphinine (4) with the same precursor leads similarly to the complex [AuCl(4)] (5). Interestingly, this complex dimerizes upon crystallization to give the bis(phosphabarrelene) complex 6, also structurally characterized. The formation of 6 results from a [4 + 2] cycloaddition between one alkynyl group of each phosphinine with the other phosphinine subunit. The formation of the cationic complex [Au(4)][GaCl4] (8) occurs under classical conditions but it disproportionates to give the cationic complex [Au(4)2][GaCl4] (9) and colloidal gold deposition. The formation of 9 has been ascertained by treating 8 with one equivalent of ligand 4. Additionally, 9 can also be obtained in a straightforward fashion by treating two equivalents of 4 with [AuCl(SMe2)] followed by treatment with GaCl3 at low temperature. The structure of 9 has been elucidated. Despite a particular arrangement of the alkyne groups which encapsulate the gold coordination sphere, no gold-alkyne interactions are visible.
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    Borane Insertion into Group-4 Metal-to-Carbon Bonds: The Reaction of HB(C6F5)2 with (η2-Formaldehyde)zirconocene Dimer and with (Butadiene)zirconocene (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2243-2247 
    Details
    ISSN: 1434-1948
    Keywords: Metallaoxirane ; HBR2 addition ; (Formaldehyde)zirconocene ; (Butadiene)zirconocene ; Heterocycles ; Boron ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (η2-Formaldehyde)zirconocene dimer (8) cleanly adds one or two molar equivalents of the borane HB(C6F5)2 by insertion of the H-[B] unit into the zirconium-carbon bond of the metallaoxirane moieties to form the mono- and bis-insertion products 16 and 17, respectively. These systems contain five-membered heterocyclic rings that are built up by connecting five different elements, namely H, B, C, O, and Zr. The bis(borane) insertion product 17 was characterized by an X-ray crystal structure analysis. (Butadiene)zirconocene reacts with HB(C6F5)2 in a similar way by insertion of the H-[B] unit into the (butadiene)C4-Zr linkage to form the metallacycle 18.
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    Complexes of Group 3 Metals and Lanthanides That Contain Siloxane-Bridged Bisaminopyridinato Ligands: Synthesis, Structure, and Application in the Ring-Opening Polymerization of Lactones (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2283-2288 
    Details
    ISSN: 1434-1948
    Keywords: N-ligands ; Yttrium ; Samarium ; Ring-opening polymerization ; Lactones ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of one equivalent of dilithiated O(SiMe2-Ap-H)2 [Ap-H = -N(2-amino-4-methylpyridine)] (1), generated in situ, with LnCl3 (Ln = Y, Sm) in THF affords O(SiMe2-Ap)2YCl(THF)2 (2) or O(SiMe2-Ap)2SmCl(THF)3 (3). In contrast, the reaction of one or two equivalents of dilithiated 1, again generated in situ, with LaBr3 in THF affords O(SiMe2-Ap)2)2LaLi(THF)3 (4). An X-ray structural analysis of 2 and 3 reveal the O(SiMe2-Ap)2- ligand to bind in a planar tetradentate manner. Equivalent Sm-N distances in 3 indicate a delocalized binding mode. Compound 2 reacts with Bu4NBH4, NaBH4 or LiCH(SiMe3)2 to give the corresponding “ate” complexes O(SiMe2-Ap)2Y(BH4)Cl(THF) Bu4N (5), O(SiMe2-Ap)2Y(BH4)2Na(THF)2 (6) and O(SiMe2-Ap)2Y(CH(TMS)2)2Li(THF)3 (7), respectively. The steric demand of the O(SiMe2-Ap)2- ligand is not large enough to stabilize monoalkyl or monoborohydride complexes. Complex 4 has been used as an initiator for the ring-opening polymerization of ε-caprolactone or δ-valerolactone. In both cases an almost linear relation between the monomer-to-initiator ratio and the molecular weight of the obtained polyester is observed. By conducting the polymerization in neat ε-caprolactone at room temperature a solid polyester block is formed after 3 min (300000 g·mol-1, Mw/Mn 2.3).
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    Silylene Reactions with Buta-1,3-diynes: Cycloadditions, Insertions, and Rearrangements (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2301-2307 
    Details
    ISSN: 1434-1948
    Keywords: Multiple bonds ; Silicon ; Silylene ; Cycloadditions ; Insertions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Di-tert-butylsilylene, generated by photolysis of hexa-tert-butylcyclotrisilane 1 or 1,1-di-tert-butyl-trans-2,3-dimethyl-silirane (2), reacts with the 1,3-diyne (tBu-C≡C-)29 to furnish the dialkynylsilane 11 via the isolable alkynylsilirene 10. Photolysis of excess 1 in the presence of 9 furnishes the C-C linked 2,2′-disilirene 12 which, upon prolonged irradiation, rearranges to the 2,5-disilabicyclo[2.2.0]hexa-1(6),3-diene (13). Treatment of 9 with diarylsilylenes, formed by irradiation of hexamethyl-2,2-dimesityltrisilane (3) or hexamethyl-2,2-bis(2,4,6-triisopropylphenyl)trisilane (4), gives the corresponding alkynylsilirenes 14 and 15, respectively. Photolysis of 1 or 2 in the presence of (Me3Si-C≡C-)216 yields the dialkynylsilane 17 which, on further reaction with 2, yields the 2,5-disilabicyclo[2.2.0]hexa-1(6),3-diene (18). Irradiation of 3 in the presence of 16 affords the cis- and trans-isomeric 1,3-dimethylene-2,4-disila-cyclobutane derivatives cis-21 and trans-21, presumably via a 1-silaallene intermediate. The structures of 12, 15, 18, cis-21, and trans-21 have been determined by X-ray crystallography.
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    Oxidation of Dichloroanilines and Related Anilides Catalyzed by Iron(III) Tetrasulfonatophthalocyanine (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2319-2325 
    Details
    ISSN: 1434-1948
    Keywords: Dichloroanilines ; Propanil ; Iron(III) tetrasulfonatophthalocyanine ; Oxidations ; Catalysts ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We investigated the degradation of polychlorinated pollutants, such as dichloroanilines and related anilides, catalyzed by iron(III) tetrasulfonatophthalocyanine (FePcS) with potassium monopersulfate or hydrogen peroxide as oxidant. The reaction is influenced by the positions of the two chloro-substituents and by the nature of the oxidant. The FePcS-catalyzed oxidation of 3,5-dichloroaniline with potassium monopersulfate leads to the formation of more biodegradable products (carboxylic acids) and to potentially toxic dimers (azo and azoxy compounds). The oxidation of 3,4-dichloroaniline by FePcS/H2O2 converts this pollutant into coupling products. The formation of dimers in the catalytic oxidation of dichloroanilines can be avoided by acylation of the amine function.
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    Amino Alcohol Coordination in Ruthenium(II)-Catalysed Asymmetric Transfer Hydrogenation of Ketones (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2335-2341 
    Details
    ISSN: 1434-1948
    Keywords: Asymmetric catalysis ; Transfer hydrogenation ; Ruthenium ; Amino alcohol ligands ; X-ray structure ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nature of ruthenium-amino alcohol precursors in the catalytic cycle of asymmetric hydrogen transfer reactions was studied using two C2-symmetrical tetradentate ligands (1 and 2) that were synthesised from (nor)ephedrine. The structure of the catalyst precursor was examined through catalysis and NMR experiments. It was shown that the active catalyst contains one ligand per metal, which coordinates in a didentate N,O fashion (9). In addition, a RuIICl2 complex, in which N,N′-bis(2-hydroxy-1-methyl-2-phenylethyl)-1,2-diaminoethane (1) coordinates through two nitrogen atoms, was structurally characterised by X-ray diffraction (8). - Based on the results of this study a series of new amino alcohol ligands was synthesised from easily available starting materials. Optimisation of the amino alcohol ligand structure resulted in the most effective chiral amino alcohol ligand (5) so far that is capable of reducing acetophenone at 0 °C with up to 97% ee in the RuII-catalysed transfer hydrogenation.
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    Novel Condensed Thionated Bis(phosphonic) Acid Salts with a Rigid Naphthalene-1,8-diyl Backbone (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2327-2333 
    Details
    ISSN: 1434-1948
    Keywords: Heterocycles ; Organo-phosphorus compounds ; Dithiadiphosphetane disulfides ; Phosphonates ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New salts of thionated (naphthalene-1,8-diyl)bis(phosphonic) acid monoanhydrides [PPh4+]2[C10H6PS2(μ-S)PS22-] (2) and [K+]2[C10H6PS2(μ-S)POS2-]·H2O (3) both containing the C3P2S ring, were prepared in high yields by the reaction of 2,4-(naphthalene-1,8-diyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide (1) with NaHS and PPh4Cl, or KOH, respectively, in water. The derivative 3, containing a P=O terminal bond as well as P-S-P bridge, undergoes, in acid conditions, a rearrangement reaction leading to the O,S-symmetrically substituted derivative [K+]2[C10H6PS2(μ-O)PS22-] (4) containing a C3P2O heterocycle. Dipotassium salt 4 was converted into the bis(tetraphenylphosphonium) salt 5 by the treating with PPh4Cl. Hydrolysis of [PyH+][C10H6P(S)(NHMe)(μ-S)PS22-] (15) led to [CH3NH3+][PyH+][C10H6POS(μ-O)POS2-]·1.5 Py (6). New compounds were characterised by 31P{1H}-, 1H- and 13C{1H}-NMR, FT-IR, ES-MS and in the cases 2-6 by X-ray structure determination. The 31P{1H}-NMR spectra of these mixed O,S-derivatives are briefly discussed.
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    Pairing Energy Effects in Cyanide Complexes of CpCrIII (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2343-2346 
    Details
    ISSN: 1434-1948
    Keywords: Chromium ; Cyanides ; Density-functional calculation ; Electronic structure ; Spin state ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The steric and electronic factors responsible for the reactivity differences between CN and Cl complexes of CpCrIII were examined by DFT/B3LYP computational techniques. The energy difference between quadruplet and doublet [CpCr(CN)2(PH3)], ΔED-Q, was calculated to be 21.2 kcal mol-1 with the LanL2DZ basis set. Although the high-spin configuration is still the ground state for the cyanide complex, the energy gap is 8.7 kcal mol-1 less than that found for the corresponding chloride species. The difference between quadruplet [CpCr(CN)2(PH3)] and doublet [CpCr(CN)2(PH3)2] less free PH3, ΔECr-P, is also smaller than for the Cl system. The components of ΔECr-P for CN and Cl were analyzed by calculating energies at fixed geometries in both spin states, which indicated that the influence of the cyanide group on the pairing energy was more important than changes in Cr-PH3 bond strength or steric effects.
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    Homogeneous and Supported Copper Complexes of Cyclic and Open-Chain Polynitrogenated Ligands as Catalysts of Cyclopropanation Reactions (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2347-2354 
    Details
    ISSN: 1434-1948
    Keywords: Cyclopropanation ; Copper ; N ligands ; Macrocycles ; Supported catalysts ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: CuI and CuII complexes of cyclic and open-chain polyaza compounds have been tested as catalysts in the benchmark cyclopropanation reaction of styrene with ethyl diazoacetate. In general, only small amounts of copper are needed to promote the reaction. The catalytic activity depends on the structure of the ligand, e.g. amine-amides are more efficient than polyamines, and on the oxidation state of copper, CuII being more active than CuI. Given that CuI is the active species, these changes of behavior must be related to the stabilities of the complexes. The nature of the counterion also has a noticeable influence on the catalytic activity, the role of which is discussed. XAS measurements suggest the formation of oligomeric species. Some of the chiral ligands lead to small enantiomeric excesses. Open-chain ligands can easily be supported on organic polymers and their complexes can be used as catalysts. Furthermore, cyclic and acyclic complexes can be supported on clays by cation exchange and the solids obtained tend to promote the reaction with a decrease in the trans/cis ratio.
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    Tetraazido Complexes of Aluminium, Gallium, and Indium (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (1999), S. 455-461 
    Details
    ISSN: 1434-1948
    Keywords: Aluminium ; Gallium ; Indium ; Azide ; Rietveld ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The new tetraazido complexes of aluminium, gallium, and indium [thf2Na][thf2Al(N3)4] (1), [py2Na][py2In(N3)4] (2), and Na[Ga(N3)4] (3) have been synthesized from MCl3 and NaN3 by salt metatheses and characterized by X-ray diffraction analysis. In compounds 1 and 2, the Group 13 metal atom and the sodium atom are each hexacoordinated by four azido groups and two additional solvent molecules. The azido groups act as μ(1,3)-bridging ligands between the Group 13 metal and sodium, thereby forming network structures. In contrast, complex 3 is solvent-free and exhibits a tetracoordinated gallium centre and a heptacoordinated sodium atom. The structure of 3 has also been investigated by means of X-ray powder data and the Rietveld method and the results are compared with the single-crystal data.
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    Azobipyridinium Dications and Radical Monocations as Acceptors (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1259-1269 
    Details
    ISSN: 1434-1948
    Keywords: Metal dithiolenes ; Charge-transfer complexes ; Azo compounds ; Electrical conductivity ; High-resolution X-ray powder diffractometry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Combination of the planar redox-active ions [ML2]2- (L = mnt2- = maleonitrile-1,2- dithiolate; M = Ni (1), Pd (2), Pt (3); dmit2- = 2-thioxo-1,3-dithiol-4,5-dithiolate: M = Ni (4), Pd (5) and trans-4,4′-azobis(1-methyl-pyridinium), (a2+) affords 1:1 ion pairs exhibiting partial and complete electron transfer as evidenced by UV-Vis and EPR spectra. Replacement of planar a2+ by a non-planar dipyridinium ketone b2+ leads to the complexes 1b and 4b. 1a, 2a, and 3a are predominantly composed of dications and dianions while 4a, 5a, and 4b are rare examples of ion pairs consisting of two radical ions. Single crystal X-ray structural analyses was performed on 4a, a(PF6)2, and a(MeSO4)2 while the structure of 1a was resolved by powder X-ray diffractometry. The latter consists of mixed stacks of planar dianions and dications forming a slipped arrangement with the centers of the two ions displaced relative to each other by 250 pm. The short interplanar distances of 340 pm are in agreement with the presence of a weak charge-transfer interaction as indicated by the corresponding absorption band at about 1400 nm. A mean reorganization energy of 0.85 ±0.04 eV is calculated from the Hush equation for complexes 1a, 2a, and 3a. No ion pair charge-transfer band is observable for 4a, 5a, and 4b. Surprisingly, in the solid state structure of 4a the [Ni(dmit)2]- monoanions do not form segregated columns as found in the many ion pairs with redox inert counterions, but prefer a mixed stack arrangement as observed also for 1a.The specific electrical conductivity of pressed powder pellets of complexes exhibiting a charge-transfer band is in the range of 2 × 10-7 to 1 × 10-5 Ω-1cm-1, increasing with increasing driving force of electron transfer in accordance with previous results. Different to that, the conductivity of the other complexes does not depend on driving force and is much higher (2 × 10-4 to 4 × 10-4 Ω-1cm-1).
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    Synthesis and Characterization of the Heterometallic Aggregate Pb2Al5(μ3-O)(μ4-O)(μ-OiPr)9(OiPr)3(μ-OAc)3 (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1291-1293 
    Details
    ISSN: 1434-1948
    Keywords: Aluminum ; Lead ; O ligands ; Alkoxy carboxylates ; Structure elucidation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel heterometallic aggregate Pb2Al5(μ3-O)(μ4-O)(μ-OiPr)9(OiPr)3(μ-OAc)3 obtained from the interaction of Pb(OAc)2 and Al(O-iPr)3 is the first structurally characterized example based on lead and aluminum. This compound has been isolated in high yield and examined by 1H-, 13C-, and 27Al NMR, and in the solid state by X-ray crystallography.
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    The First Oligomeric Samarium(II) Silylamide: Coordinative Saturation through Agostic Sm···SiH Interactions (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1405-1407 
    Details
    ISSN: 1434-1948
    Keywords: Agostic interactions ; Samarium ; Silylamide ; Transsilylamination ; Trinuclear complex ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sm[N(SiMe3)2]2(thf)2 reacts with 1,1,3,3-tetramethyldisilazane by a transsilylamination reaction to form the hexane-soluble Sm[N(SiHMe2)2]2(thf)x in high yield. An X-ray diffraction study reveals a novel trinuclear complex of composition Sm{[μ-N(SiHMe2)2]2Sm[N(SiHMe2)2](thf)}2 featuring a bent array of metal centers. Multiple metal···SiH β-agostic interactions sterically and electronically saturate the samarium(II) centers implying a new coordination mode of the bridging amide ligands.
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    Absorption and Emission Properties of Di- and Trinuclear Ruthenium(II) Rack-Type Complexes (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1409-1414 
    Details
    ISSN: 1434-1948
    Keywords: Ruthenium complexes ; Luminescence ; Bridging ligands ; Terpyridine ligands ; Polynuclear metal complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The absorption spectra and the luminescence properties of three dinuclear RuII complexes and one trinuclear RuII complex have been investigated. All the complexes have rack-type structures. The dinuclear complexes 1, 2, and 3 incorporate a bis-tridentate bridging ligand made up of a pyrimidine and four pyridine moieties, as well as two 2,2′:6′,2′-terpyridyl (tpy) ligands. The trinuclear complex 4 incorporates a tris-tridentate bridging ligand made up of two pyrimidine and five pyridine moieties, as well as three tpy ligands. The absorption spectra of the complexes show a large number of ligand-centered (LC) and metal-to-ligand charge-transfer (MLCT) bands. All the complexes exhibit emission from a triplet MLCT state, with maxima in the spectral range 840-950 nm (lifetimes between 40 and 80 ns) at 298 K in fluid solution, and in the spectral range 760-810 nm (lifetimes between 2 and 3 μs) at 77 K in rigid matrices. A fine tuning of the absorption and luminescence properties of complexes 1-3can be achieved by changing the substituents on the pyrimidine ring of the bridging ligand. Efficient energy transfer within the rack structure 4 occurs from the (upper-lying) central metal-based chromophore to the (lower-lying) peripheral ones.
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    Dynamic Combinatorial Chemistry: Substrate H-Bonding Directed Assembly of Receptors Based on Bipyridine-Metal Complexes (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1415-1420 
    Details
    ISSN: 1434-1948
    Keywords: Combinatorial chemistry ; Molecular recognition ; Functionalized bipyridine metal complexes ; Janus molecules ; Hydrogen bonding ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The functionalized ligands 1 and 2 bearing hydrogen-bonding recognition groups have been synthesized. Their assembly by metal ions such as CuI and PdII having different coordination geometries generates different receptor architectures for the binding of suitable substrates. Addition of the complementary bis(imide) Janus molecules (4-7) to [1a, 2a, CuTf] or to [1b, 2b, Pd(BF4)2] mixtures leads to a moderate selective increase of the fraction of the [(1a)2Cu]+ or [(1b)2Pd]2+ complex depending on the Janus substrate used. Largest enhancements are observed for those Janus substrates that may be expected to display highest geometrical complementarity with the two complexes. These results represent a process directed by target binding based on dynamic combinatorial chemistry.
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    Chiral Rhenium Complexes of Functionalized Thioaldehydes (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1435-1443 
    Details
    ISSN: 1434-1948
    Keywords: Captopril ; Cysteine ; Rhenium ; S ligands ; Thioaldehydes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiral racemic rhenium thioaldehyde complexes [CpRe(NO)(PPh3)(η2-S=CHR)]PF6 (2a-g) bearing functionalized aliphatic groups R [R = CH2Ph (a), COOEt (b), CH2COOMe (c), CH2C(O)NHCH2Ph (d), (R)-CH(NC8H4O2)COOMe (e), (S,S)-CH(Me)C(O)NC4H7COOMe (f), C4H3O (g)] have been obtained by hydride abstraction from the corresponding thiolate complexes [CpRe(NO)(PPh3)(SCH2R)] (1a-g). With the exception of 2b, only single stereoisomers with like configurations at rhenium and the thioaldehyde carbon atom were obtained. In some cases, the corresponding sulfinate complexes [CpRe(NO)(PPh3)(SO2CH2R)] (3d-f) were formed as by-products. The analogous toluenesulfinate complex [CpRe(NO)(PPh3){SO2(4-C6H4CH3)}] (3a) has been prepared from [CpRe(NO)(PPh3)(THF)]BF4 (8), and the structure of 3e has been determined by X-ray crystallography. The use of phosphorus ligands other than PPh3 was briefly explored with the synthesis of [CpRe(NO)(PR′3)(η2-S=CHR)]PF6 (5a-d) [R′ = OPh, R = Ph (a), 4-C6H4Cl (b), R′ = iPr, R = Ph (c), H (d)]. Nucleophilic addition of NaSMe to [CpRe(NO)(PPh3){η2-S=CH(4-C6H4OMe)}]PF6 (5e) gave the dithioacetal complex [CpRe(NO)(PPh3){SCH(SMe)(4-C6H4OMe)}] (9) in high yield and with low diastereoselectivity. Diels-Alder additions of 5a, e with 2,3-dimethylbutadiene and 2,3-dimethoxy-butadiene gave complexes of cyclic thioethers (10a-c). From the relative rates of reaction (5a 〉〉 5e) and the low diastereoselectivity, it was concluded that the cycloadditions as well as the nucleophilic addition proceed via the linkage isomers [CpRe(NO)(PR′3)(η1-S=CHR)]PF6.
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    Group 5 Metal Complexes with Cyclooctatetraene: Formation and Characterization of (Butadiene)(cyclooctatetraene)(cyclopentadienyl)tantalum Systems (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1461-1466 
    Details
    ISSN: 1434-1948
    Keywords: Diene complexes ; η3-Cyclooctatetraene metal complex ; B(C6F5)3 addition ; Tantalum ; Bicyclo[5.1.0]octadienyl metal complex ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The [(η4-diene)(η5-RCp)TaCl2] complexes 6a-e (diene = butadiene, isoprene or 2,3-dimethylbutadiene; RCp = pentamethylcyclopentadienyl, methylcyclopentadienyl or cyclopentadienyl) react with cyclooctatetraene dianion (employed as [(cot)Li2]) to yield the (η4-diene)(η3-cyclooctatetraene)(η5-RCp)tantalum complexes 7. The η3-cot coordination was confirmed by an X-ray crystal structure analysis of the compound [(supine-s-cis-η4-C4H6)(η3-cot)(η5-Cp*)Ta] 7a. In solution, the cot ligand of all the complexes 7 is fluxional. Two isomers [supine and proneorientation of the (diene)CpTa subunit] were found for the (η4-butadiene)(η3-cot)CpTa system (7e/7e′ = 95:5). Complex 7e cleanly adds the organometallic Lewis acid B(C6F5)3 to yield the betaine system [(η4-C4H6){C8H8B(C6F5)3}Cp*Ta] 8, which contains a substituted bicyclo[5.1.0]octadienyl ligand.
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    Synthesis and Metal-Ion Extraction Properties of para-tert-Butylcalixareneglycine Ester Acetamides (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1557-1562 
    Details
    ISSN: 1434-1948
    Keywords: Calixarenes ; Macrocycles ; Silver ; Radiotracer technique ; Metal-ion extraction ; Radiochemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Calixareneglycine ester acetamides 4a-c have been synthesized from calixareneacetyl chlorides 5a-c and glycine ethyl ester (6). Their ion-binding properties have been investigated by liquid-liquid extraction with radiotracer techniques. The experiments reveal a moderate affinity towards silver(I) ions, which increases with calixarene ring size.
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    Extrusion of rotating microtubules on the dynein-track from a microtubule-dynein γ-complex (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 30 (1995), S. 17-25 
    Details
    ISSN: 0886-1544
    Keywords: rotation ; twisting ; microtubule-dynein complex ; 22S dynein ; dynein-track ; ATP ; sliding ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Applying a new in vitro motility assay system for microtubules and 22S dynein, we recently reported on an ATP-induced extrusion of microtubules from microtubule-dynein α- and β-complexes [Mimori and Miki-Noumura, 1994:Cell Motil. Cytoskeleton 27:180-191]. In the present study, we prepared a γ-complex by copolymerizing porcine brain tubulin and Tetrahymena ciliary 22S dynein, and examined the ATP-induced microtubule movement from the γ-complex. The extrusion process appeared quite similar to that of the β-complex. The sliding velocity was 18.39 ± 2.20 m̈m/sec, which was a value comparable to that of trypsin-digested flagellar axonemes [Yano and Miki-Noumura, 1980:J. Cell Sci. 44:169-186]. Higher velocity may be due to a densely arranged dynein-track with the same polarity, which was detached from the γ-complex and absorbed in rows on a glass surface of the slide. Sometimes a free-floating microtubule in the perfusion chamber was observed riding and sliding on the dynein-track remaining on the slide after extrusion.Unexpectedly, we found that when the front part of the microtubule was fixed to a glass surface, a continuous sliding microtubule at the rear part on the dyneintrack often transformed into a left-handed helix, and subsequently a twisted helix with several turns. The helix formation may be due to some rigidity in the microtubule and a right-handed torque component in the sliding force of 22S dynein. The addition of ATP may release some distortion accumulated in the complex structure during copolymerization of tubulin and 22S dynein, inducing reverse rotation of the microtubule. © 1995 Wiley-Liss, Inc.
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    cAMP/ATP relationship in the activation of trout sperm motility: Their interaction in membrane-deprived models and in live spermatozoa (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 31 (1995), S. 159-176 
    Details
    ISSN: 0886-1544
    Keywords: trout ; spermatozoa ; ATP ; cAMP ; axoneme ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Live trout spermatozoa initiate flagellar motility for only a short period (30 sec at 18°C) during which their mean beat frequency decreases steadily from 60 to 20 Hz. Motility then stops abruptly. Investigations of the activation of movement in demembranated sperm points to cyclic-AMP being necessary for reactivation (half effect at 0.5μm) in some conditions. cAMP acts mainly by increasing the percentage of motile cells and not the beat frequency (BF) of the flagellar axoneme. Dibutyryl cAMP does not initiate movement or prolong motility of live sperm.The initiation of movement of demembranted trout sperm was investigated in various incubation conditions relative to previous phases of in vivo movement and to ATP concentration. In the absence of cAMP and in the presence of ATP lower than 25 μM, all sperm celi models were active with BF up to 15-20 Hz whatever their previous physiological condition. In contrast, at ATP concentrations above 100 μM, the fraction of active spermatozoa decreased proportionally but the BF of the active ones increased so that, at 1 mM ATP up to 20 μM restored activity to 100% sperm models with a similar BF of 65 Hz.At ATP concentrations higher than 25 μM, cAMP was necessary in a concentration dependent manner in the reactivation, but not in the demembranation meduim. This dependence was found to be unrelated to a previous in vivo phase of movement. The antagonistic effects of ATP vs. cAMP were tested at various concentrations of both nucleotides: the apparent affinity for cAMP, measured as the concentration restoring movement of 50% cell models, was decreased from 15 nM at 0.1 mM ATP to 0.5 μM at 1 mM ATP; conversely, the affinity for ATP, measured as the concentration giving rise to the half maximal beat frequency, was not significautly affected when the concentration of cAMP was raised to 0.5 mM. Preincubation with phosphodiesterase (PDE) resulted in motility of 100% of sperm models even at low ATP concentration. This tends to show that cAMP must be constantly present to sustain motility.
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    Role of the cytoskeleton in the reaction of fibroblasts to multiple grooved substrata (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 31 (1995), S. 147-158 
    Details
    ISSN: 0886-1544
    Keywords: actin ; contact guidance ; microfilaments ; microtubules ; orientation ; cytochalasin ; colcemid ; taxol ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The role of the cytoskeleton and cell attachments in the alignment of baby hamster kidney fibroblasts to ridge and groove substratum topography was investigated using confocal scanning microscopy. This was carried out with normal cells and cells treated with the cytoskeleton modifiers cytochalasin D, colcemid, and taxol. Actin was localised with fluorescent phalloidin. Tubulin, Vinculin, and intracellular adhesion molecule-1 were visualised by indirect immunofluoresence. The spreading, elongation, and orientation of the cells after 24 h of culture in these conditions were measured on grooves of 5, 10, and 25 μm width and 0.5, 1, 2, and 5 μm depth. We have also observed events over the first 30 min of cell attachment. Five minutes after cell attachment, F-actin condensations were seen close to the intersection of groove wall and ridge top, that is, at a topographic discontinuity. The condensations were often at right angles to the groove edge and showed a periodicity of 0.6 μm. Vinculin arrangement at the early stages of cell spreading was similar to that of actin. Organisation of the microtubule system followed later, becoming obvious at about 30 min after cell plating. The Curtis and Clark theory (that cell react to topography primarily at lines of discontinuity in the substratum by actin nucleation) is supported by these results. The use of cytoskeletal poisons did not entirely abolish cell reaction to grooves. Colocemid increased cell spreading and reduced cell orientation and elongation. Cytochalasin D reduced cell spreading, orientation, and elongation. Taxol reduced cell elongation but did not affect cell spreading and orientation. We conclude that the aggregation of actin along groove/ridge boundaries is a primary driving event in determining fibroblast orientation on microgrooved substrata.
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    Masthead (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 30 (1995) 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1002/cm.970300201
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    Desmosome assembly and disassembly are regulated by reversible protein phosphorylation in cultured epithelial cells (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 30 (1995), S. 108-121 
    Details
    ISSN: 0886-1544
    Keywords: intercellular junctions ; desmosome ; assembly ; kinase ; phosphatase ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Desmosomes are one component of the intercellular junctional complex in epithelia. In cultures of epithelial cells, desmosome assembly can be regulated by modulating the calcium concentrations of the growth media. At present, very little is known about the intracellular signal transduction mechanisms that regulate desmosome assembly and disassembly in response to changing extracellular calcium concentrations. We have used inhibitors of protein kinases and phosphatases in a combined biochemical and morphological approach to analyze the role of protein phosphorylation in the assembly and disassembly of desmosomes in Madin-Darby canine kidney epithelial cells. Our results suggest that desmosomal proteins (desmoplakins I/II and desmoglein 1) are primarily phosphorylared on serine residues. Electron microscopic analyses of desmosome assembly upon induction of cell-cell contact, in the presence of protein kinase inhibitor, H-7, revealed an apparently normal assembly of desmosomes. However, complete disassembly of desmosomes was inhibited by H-7 upon removal of extracellular calcium. Under these conditions, although desmosomes split, desmosomal plaques and their associated cytokeratin filaments can not be internalized. In contrast, treatment of the cultures with okadaic acid (OA), an inhibitor of protein phosphatases, inhibited desmosome assembly but had no effect on disassembly. In addition, the inhibitory effect of okadaic acid on desmosome assembly was specific to this junction since we observed apparently normal tight junction and adherens junction in okadaic acid-treated cultures. These results suggest that via reversible protein phosphorylation involving both protein kinase and protein phosphatases. © 1995 Wiley-Liss, Inc.
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    Exogenous gelsolin binds to sarcomeric thin filaments without severing (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 31 (1995), S. 196-206 
    Details
    ISSN: 0886-1544
    Keywords: gelsolin ; actin ; myofibrils ; immunofluorescence ; nebulin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have investigated the binding of gelsolin to thin myofilaments in situ and their stability against severing. Differentiated myotubes from chicken skeletal muscle containing cross-striated myofibrils were permeabilized with Triton X-100 and incubated with gelsolin. Immunoflurorescence microcopy localized both endogenous and exogenous gelsolin in the I-Z-I-regions of the sarcomers. The staining pattern suggested a binding of the exogenous gelsolin along the entire length of the thin filaments. This binding was Ca2+ dependent, but gelsolin was not removed after subsequent addition of EGTA. The fluorescence staining for actin remained unchanged after gelsolin incubation, indicating that thin filaments in cross-striated myofibrils were resistant to the severing action of gelsolin, in contrast to the microfilaments in stress fibers. After extraction of the permeabilized cells with high ionic strength to remove tropomyosin and myosin, gelsolin stell bound along the entire thin filament and the actin pattern also remained unchanged. After Triton X-100 permeabilization and high ionic strength extraction, the giant protein nebulin was found to be still present as a myofibrillar component. Gelsolin treatment after high salt extraction affected neither actin nor nebulin in the thin filaments. We therefore conclude that nebulin confers the gelsolin resistance to the sarcomeric actin filaments.
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    URL: http://dx.doi.org/10.1002/cm.970310303
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    Novel mode of hyper-oscillation in the paralyzed axoneme of a chlamydomonas mutant lacking the central-pair microtubules (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 31 (1995), S. 207-214 
    Details
    ISSN: 0886-1544
    Keywords: flagella ; Chlamydomonas ; mutant ; high-frequency vibration ; nanometer-scale measurement ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The flageliar axoneme of the mutant pf18 lacking the central pair does not beat, but undergoes a nanometer-scale, high-frequency oscillation (hyper-oscillation) in the presence of ATP [Yagi et al., 1994: Cell Motil, Cytoskeleton 29:177-185]. The present study demonstrates that the amplitude of the hyper-oscillation increases significantly in the simultaneous presence of ATP and ADP. In addition, the hyper-oscillation under these conditions sometimes takes on an exceptionally simple asymmetric pattern, in which the maximal shearing velocity exceeds 50 μm/sec, much higher than the maximal velocity of ordinary dynein-microtubule sliding. The asymmetric oscillation thus appears to be at least partly driven by an internal elastic force. Its amplitude suggests that the axoneme has an elastic component that can be stretched by as long as 0.1 μm. Analyses of the asymmetric pattern further suggests that the axonemal dyneins have a tendency to attach to and detach from the doublets cooperatively and that the mechanochemical cycle of dynein has an inherent refractory period of about 2 msec, during which dynein cannot interact with microtubules.
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    Traction forces in locomoting cells (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 31 (1995), S. 225-240 
    Details
    ISSN: 0886-1544
    Keywords: cell-substratum adhesion ; lamellar contractility ; locomotion ; silicone rubber ; traction forces ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A means of determining quantitative maps of the tractions exerted by locomoting cells on a substratum has been developed. This method is similar to the Harris silicone substratum assay [Harris et al., 1980: Science 208:177-179], but uses an improved non-wrinkling film that deforms more predictably in response to traction forces. The method also utilizes a mathematical analysis of rubber deformation to produce the final map of the distribution of tractions. The resulting maps consistently showed that fish keratocytes exert a steady-state “pinching” on the substratum, perpendicular to the cell's direction of locomotion. No significant rearward tractions were detected at or near the front edge of the cell. Likewise, no significant forward tractions associated with peeling of adhesions were found at the back of the cell. A second assay uses deflection of a lightly attached glass microneedle to measure the total force exerted by locomoting cells. Forces of approximately 4.5 × 10-3 dyn were required to “stall” locomoting keratocytes. The implications of these findings for cell movement are discussed.
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    Dynamics of triton-insoluble and triton-soluble F-actin pools in calcium-activated human polymorphonuclear leukocytes: Evidence for regulation by gelsolin (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 30 (1995), S. 136-145 
    Details
    ISSN: 0886-1544
    Keywords: microfilamentous cytoskeleton ; actin binding proteins ; actin polymerization ; annealing ; non-muscle cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Gelsolin, a Ca++ activated, 90 kd actin binding protein, can regulate actin polymerization in polymorphonuclear leukocytes (PMNs) via severing of filaments to dissolve gels or by capping of filament ends to limit polymerization. In Triton-lysed PMNs, 30% of gelsolin is bound to the Triton-soluble F-actin (TSF) pool and none is bound to the Triton-insoluble F-actin (TIF) pool. Calcium-activated PMNs exhibit concurrent temporal and quantitative TIF growth and TSF and total F-actin loss. To determine if gelsolin plays a role in regulating TSF pool size, we monitored gelsolin-actin interactions and TIF, TSF and G-actin content at 5 second intervals in PMNs activated with the calcium ionophore, ionomycin. Actin pools were measured by NBDphallacidin binding and by gel scans and expressed relative to basal; gelsolin-actin interactions were measured as change in the amount of EGTA-resistant gelsolin:actin (G:A) complexes and by immunoblot quantification of gelsolin in actin pools. In basal PMNs, 33% of PMN gelsolin is bound in 1:1 EGTA-resistant G:A complexes and TSF and TIF retain 30% and 0% of PMN gelsolin, respectively. By 20 seconds after ionomycin addition, TSF decreases, TIF increases and a fraction of gelsolin repartitions from the TSF to the TIF pool. At maximum change (60 seconds), total F-actin (TIF + TSF) and TSF decrease and TIF increases by 25%; gelsolin is bound to both TSF and TIF (35% of total gelsolin in each pool), and 1:1 EGTA-resistant G:A complexes increase from 33% to 70%. No changes occur in cells activated by ionomycin in the absence of Ca++. The data show Ca++ activated TIF growth and TSF loss are temporally and quantitatively associated with an increase in the percent of gelsolin bound to actin and the translocation of gelsolin from TSF to TIF. This is unique, since no other PMN activator is known to repartition gelsolin into TIF actin. Further, the Ca++ activated initial increase in TIF concurrent with a fall in TSF without a change in total F-actin or G-actin content suggest that TIF grows initially only by TSF annealing/cross-linking to TIF. Gelsolin may regulate these events. © 1995 Wiley-Liss, Inc.
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    Kinesin does not support the motility of zinc-macrotubes (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 30 (1995), S. 146-152 
    Details
    ISSN: 0886-1544
    Keywords: zinc-sheets ; macrotubes ; kinesin ; electron microscopy ; microtubules ; tubulin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Moving along a microtubule, kinesin follows a course parallel to the protofilaments; but it is not known whether kinesin binds exclusively on a single protofilament. The presence of zinc during tubulin polymerization induces sheets where neighboring protofilaments are antiparallel. If kinesin could support the motility of these zinc-sheets, then the binding site for a kinesin molecule would be limited to a single protofilament.Kamimura and Mandelkow [1992: J. Cell Biol. 118:865-75] reported that kinesin moves along zinc-sheets. We found that zinc-sheets grown under their conditions often had a microtubule-like structure along one edge. We confirmed the possibility that the motility observed by Kamimura and Mandelkow [1992: J. Cell Biol. 118:865-75] is attributed to the microtubule-like structure rather than the zinc-sheet.To resolve the question of whether kinesin can recognize an antiparallel protofilament lattice, we investigated the kinesin-mediated motility of zinc-macrotubes. At higher free zinc concentrations, zinc-sheets roll up as macrotubes, free of edges. In the presence of 10 m̈M taxol and 100 nM free Zn2+ at pH 6.8, the samples were shown by electron microscopy to contain only macrotubes. Under these buffer conditions, kinesin could bind strongly to axonemal doublets in the presence of AMP-PNP, and generate motility in the presence of ATP, but kinesin did not bind to nor move the macrotubes. This shows that kinesin cannot bind efficiently to nor move on the anti-parallel lattice; it is possible (though not necessary) that the groove between two parallel protofilaments is required for kinesin's motility. © 1995 Wiley-Liss, Inc.
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    Masthead (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 30 (1995) 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1002/cm.970300301
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    Comparative study of the colchicine binding site and the assembly of fish and mammalian microtubule proteins (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 30 (1995), S. 153-163 
    Details
    ISSN: 0886-1544
    Keywords: colchicine binding site ; MTC ; cod microtubules ; bovine microtubules ; MAPs ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Isolated microtubules from cod (Gadus morhua) are apparently more stable to colchicine than bovine microtubules. In order to further characterize this difference, the effect of the colchicine analogue 2-methoxy-5-(2,3,4-trimethoxyphenyl)-2,4,6-cyclo heptatrien-1-one (MTC) was studied on assembly, as measured by turbidity and sedimentation analysis, and on polymer morphology. MTC has the advantage to bind fast and reversible to the colchicine binding site of tubulin even at low temperatures. It was found to bind to one site in cod brain tubulin, with affinity (6.5 ± 1.5) × 105M 1at both low or high temperature, similarly to bovine brain tubulin. However, the effect of the binding differed. At substoichiometric concentrations of MTC bovine brain microtubule assembly was almost completely inhibited, while less effect was seen on the mass of polymerized cod microtubule proteins. A preformed bovine tubulin-colchicine complex inhibited the assembly of both cod and bovine microtubules at substoichiometric concentrations, but the effect on the assembly of cod microtubules was less. At higher concentrations (5 × 10-5 to 1 × 10-3M), MTC induced a large amount of cold-stable spirals of cod proteins, whereas abnormal polymers without any defined structure were formed from bovine proteins. Spirals of cod microtubule proteins were only formed in the presence of microtubule associated proteins (MAPs), indicating that the morphological effect of MTC can be modulated by MAPs. The effects of colchicine and MTC differed. At 10-5M colchicine no spirals were formed, while at 10-4M and 10-3M, a mixture of spirals and aggregates was found. The morphology of the spirals differed both from vinblastine spirals and from the spirals previously found when cod microtubule proteins polymerize in the presence of high Ca2concentrations. The present data show that even if the colchicine binding site is conserved between many different species, the bindings have different effects which seem to depend on intrinsic properties of the different tubulins. © 1995 Wiley-Liss, Inc.
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    Cytoskeleton of the Drosophila egg chamber: New observations on microfilament distribution during oocyte growth (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 31 (1995), S. 298-306 
    Details
    ISSN: 0886-1544
    Keywords: Drosophila ; nurse cells ; oocyte ; microfilaments ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The distribution of microfilaments in Drosophila egg chambers stained with rhodamine (Rh)-conjugated phallcidin was studied by laser scanning confocal microscopy and transmission electron microscopy. These techniques revealed new details in the pattern of microfilament localization. We observed in stage 1-3 egg chambers accumulation of filamentous actin in the oocyte cytoplasm between the ring canals connecting the oocyte with adjacent nurse cells. Starting from stages 6-7 short microfilament bundles arranged in basket-like structures were associated with the side of the ring canals facing the nurse cell cytoplasm. We also observed a dramatic decrease in the actin network associated with the cortex of the oocyte in stage 10. During stage 10B the nurse cell cytoplasm was crossed by radial actin bundles that showed a sarcomeric-like cross striation after Rh-phalloidin staining. The ring canals also did not uniformly stain but showed a punctate labeling. The implications of the actin cytoskeleton during oocyte growth are discussed. © 1995 Wiley-Liss, Inc.
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    Porcine brain neurofilament-H tail domain kinase: Its identification as cdk5/p26 complex and comparison with cdc2/cyclin B kinase (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 31 (1995), S. 283-297 
    Details
    ISSN: 0886-1544
    Keywords: neurofilament ; phosphorylation ; cdk5 ; cdc2 ; cyclin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Using dephosphorylated neurofilament (NF) proteins as substrates, the kinase with a higher activity for in the dephosphorylated NF-H than the phosphorylated form of NF-H was searched for in the porcine brain extract. Most NF-H kinase activity in the brain extract pelleted with microtubules. The NF-H kinase purified from a high salt extract of the microtubule pellets was composed of cdk5 and a 26 kDa protein, a fragment of the 35 kDa regulatory subunit of cdk5. In contrast to the association of the active kinase with microtubules, each of uncomplexed cdk5 and the 35 kDa regulatory subunit was differently distributed in the supernatant fraction and the pellet, respectively, by ultracentrifugation of the brain extract. Dephosphorylated forms of NF-H and NF-M became reactive to antibodies recoginizing in vivo phosphorylation sites (SM131, 34, and 36, JJ31 and 51) by phosphorylation with cdk5/p26. cdk5/p26 showed similar enzymatic properties to p34cdc2/cyclin B kinase; the substrate specificity and inhibition by a p34cdc2 kinase specific inhibitor, butyrolactone I. However, p34cdc2/cyclin B kinase was distinguished from cdk5/p26 by its binding to p13suc1 protein and by its reactivity to anti-p34cdc2 antibodies. In spite of similar enzymatic properties of cdk5/p26 and p34cdc2/cyclin B kinase, cdk5/26 did not display M-phase promoting activity when assayed with a cell-free system of Xenopus egg extract. © 1995 Wiley-Liss, Inc.
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    Functional dissection of the dynein motor domain (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 32 (1995), S. 133-135 
    Details
    ISSN: 0886-1544
    Keywords: cytoplasmic dynein ; motor domain ; mutational analysis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The highly conserved lysine residue in the putative hydrolytic ATP-binding motif of the yeast cytoplasmic dynein heavy chain was replaced with leucine. The mutation was generated by a two-stage transformation method designed for genomic site-directed mutagenesis. Preliminary observations show that the effects of this alteration on the cellular roles of dynein are indistinguishable from those of a disruption mutation in which the entire motor domain is not expressed. © 1995 Wiley-Liss, Inc.
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    Masthead (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 32 (1995) 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    Over-expression of smooth muscle caldesmon in mouse fibroblasts (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 32 (1995), S. 233-243 
    Details
    ISSN: 0886-1544
    Keywords: caldesmon ; over-expression ; cell cycle ; motility ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Caldesmon is an actin, calmodulin, tropomyosin, and myosin binding protein implicated in the regulation of actomyosin interactions. We have invesigated the effect of overexpression of the higher molecular weight smooth muscle isoform of caldesmon on mouse L cell physiology. Mouse L(TK-) cell were transfected stably with plasmids carrying the TK+ gene and a full length human smooth muscle caldesmon cDNA under control of the adenovirus major late promoter. Two clones displaying four and eight times the level of the endogenous mouse high molecular weight caldesmon were isolated. These cells acquire a distinct phenotype characterized by an altered morphology, including an increased number of processes and larger area due to enhanced cell spreading, and a significantly slower growth rate than that of untransfected control cells, or cells transfected with the TK+ gene alone. The majority of the overexpressed caldesmon appears to be active and localized on cytoskeleton structures as determined by detergent lysis. Immuno-fluorescence analysis of the clones revealed that the caldesmon is localized as punctate staining on stress-fibers and in membrane ruffles. The immunofluores-cence images suggest that caldesmon overexpressing cells have more total filaments than control cells. The effects of excess caldesmon on cell mobility are ambiguous: one clone displayed increased motility compared to the control, while the motility of the second clone was decreased relative to the control. © 1995 Wiley-Liss, Inc.
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    Plakoglobin: Kinetics of synthesis, phosphorylation, stability, and interactions with desmoglein and E-cadherin (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 32 (1995), S. 258-272 
    Details
    ISSN: 0886-1544
    Keywords: adhering junctions ; desmosome ; assembly ; phosphorylation ; protein interaction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have analyzed the kinetics of synthesis, phosphorylation, and stability of the soluble and insoluble plakoglobin (PG) and their interactions with Dsg1 and E-cadherin in Madin-Darby canine kidney (MDCK) epithelial cells in the absence of cell adhesion and after the induction of cell-cell contact. Using a combination of biochemical and morphological approaches, we show that newly synthesized PG enters a soluble:insoluble pool of proteins in a 60:40 ratio regardles of cell-cell contact. Following synthesis, PG is increasingly found in the insoluble pool. Although cell-cell contact does not effect either the size of each pool or the rate or efficiency of the transfer from the soluble into the insoluble pool, it results in a significant increase in the metabolic stability of the newly synthesized insoluble PG. The soluble PG initially forms separate complexes with E-cadherin and Dsg1. PG-Dsg1 complexes become insoluble and localize to the desmosome. PG-E-cadherin complexes remain soluble and are distributed intracellularly. The insoluble PG and E-cadherin detected at the cell periphery remain distinctly separate, as demonstrated previously [Hinck et al., 1994: J. Cell Biol. 125:1327-1340; Nathke et al., 1994: J. Cell Biol. 125:1341-1352]. In addition, we detected a separate pool of PG which is not associated with either Dsg1 or E-cadherin and after the induction of cell-cell contact becomes primarily insoluble and is distributed along the lateral membrane. Phoshorylation analysis showed that there is a significantly greater amount of phosphorylated PG in the soluble pool than in the insoluble pool. In addition the soluble pool is both serine and theronine phosphorylated, whereas the insoluble PG is primarily phosphorylated on serine residues. © 1995 Wiley-Liss, Inc.
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    Polarity and nucleation of microtubules in polarized epithelial cells (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 32 (1995), S. 273-288 
    Details
    ISSN: 0886-1544
    Keywords: microtubules ; γ-tubulin ; polarized epithelia ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Microtubules oriented in the apicobasal axis of columnar epithelial cells arranged with a uniform polarity with minus ends toward the apical surface, suggesting that these cytoskeletal filaments might serve as a substrate for polarized movement of membrane vesicles within the cell. It is not known whether hepatocytes, a cuboidal epithelium in which transcellular transport is a requisite step in normal apical membrane biogenesis, contain microtubules arranged with a similar polarity. In the present study, we explore the question of microtubule polarity and possible mechanisms for nucleation in the epithelial cell lines WIF-B (hepatocyte), Caco-2 (intestine), and Madin-Darby canine kidney (MDCK). Caco-2 microtubules in the apicobasal axis had uniform polarity with minus ends nearest the apical surface. After cold and nocodazole-induced depolymerization, microtubule regrowth initiated in the apical region in all three cell types. The apex of WIF-B and Caco-2 cells contained two pools of γ-tubulin: one associated with centrosomes and the other delocalized under the apical membrane. Non-centrosomal γ-tubulin was present in complexes that sedimented between 10S and 29S; both forms could bind microtubules. The presence of both centrosomal and noncentrosomal γ-tubulin in apical cytoplasm suggests multiple mechanisms by which microtubule nucleation might occur in epithelial cells. © 1995 Wiley-Liss, Inc.
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    Cytochalasin J affects chromosome congression and spindle microtubule organization in PtK1 cells (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 32 (1995), S. 245-257 
    Details
    ISSN: 0886-1544
    Keywords: actin ; cytochalasin ; microfilaments ; microtubules ; mitosis ; mitotic apparatus ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: PtK1 cells were treated with 10 μg/ml cytochalasin J (CJ) for 15 min at various stages of mitosis. When applied at nuclear envelope breakdown (NEB) chromosome congression was blocked or substantially slowed, and chromosomes failed to show organization patterns typical of prometaphase. Spindle microtubule (MT) numbers appeared unaffected as judged by the pattern of birefringent retardation. However, ultrastructural analysis showed MTs to be reorganized within the spindle domain with some exhibiting fragmentation and others failing to interact with poorly defined kinetochore laminae. The spindle domain took on a curved, almost banana-like shape, as related to the position of the centrosomes and lack of orientation of chromosomes. Serial section analysis of kinetochore regions showed reduced contour length and maturation of the kinetochore plate with few MTs associated with this structure. Cells similarly treated with 10 μg/ml CJ at NEB for 15 min and then released into conditioned medium for 15 min showed that most chromosomes resumed congression to the metaphase plate. Ultrastructural analysis revelaed a more normal organization of spindle MTs, but kinetochore structure remained affected. CJ treatment of cells in prometaphase slightly affected chromosome congression with most chromosomes aligning at the metaphase plate after 10-15 min of treatment. Ultrastructural analysis showed that astral MTs were disrupted and spindle MTs were fragmented; few MTs coursed from kinetochore to pole. Kinetochore structure was also affected with only small numbers of short MTs seen associated with kinetochores. Application of CJ at anaphase onset had little effect on anaphase A and B, but cytokinesis failed to occur. Anti-tubulin staining of a monolayer of cells treated with 10 μg/ml CJ for 15 min showed that over 60% of mitotic figures exhibited changes in MT organization. Cells showing the greatest effect of treatment had several foci of bundles of MTs, as if the spindle were multipolar. Chromosomes were arranged near the periphery of the spindle which could be a result of abnormalities of kinetochore structure. Improper association of spindle MTs with kinetochores and, thus, changes in kinetochore position could account for these changes in spindle architecture. © 1995 Wiley-Liss, Inc.
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    Analysis of the interdependent localization of vimentin and microtubules in neoplastic myoepithelial cells (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 32 (1995), S. 289-298 
    Details
    ISSN: 0886-1544
    Keywords: cytoskeleton ; intermediate filaments ; vimentin ; microtubules ; myoepithelial cells ; immunofluorescence ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Salivary gland neoplastic myoepithelial cells in culture form very thin cytoplasmic processes in which the vimentin network is well dispersed. These vimentin filaments can be individually visualized by immunofluorescence. In this study, we have analyzed the role of microtubules in the distension and organization of the vimentin filament network found in these cells. We find that vimentin filaments colocalize along microtubules; however, a significant number of filaments can also be found in microtubule-free domains. Additionally, vimentin filaments are absent from large domains of microtubule inhibitor nocodazole did not cause any retraction of the distended vimentin network. This observation suggests that the structural integrity of microtubules is not important for the stability of the vimentin network. Combining procedures for transient disruption of vimentin filaments and microtubules we observed that, in the absence of microtubules, the vimentin network could reassemble in the perinuclear region but was unable to extend toward the cell periphery. The dispersion of vimentin filaments to the peripheral regions of the cytoplasm could only be observed upon microtubule reassembly. This indicates that microtubules are not required for the stability of the vimentin network, but the dispersion of vimentin filaments to the peripheral cytoplasm depends on active interactions with microtubules. © 1995 Wiley-Liss, Inc.
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    Changes of cell behavior by near-infrared signals (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 32 (1995), S. 299-304 
    Details
    ISSN: 0886-1544
    Keywords: 3T3 cells ; CV1 cells ; cell motility ; infrared ; photobiology ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: 3T3 mouse fibroblasts responded differently to specific near-infered signals than epithelial CV1 cell. Furthermore, signals with the same wavelength and energy changed the percentages of attracted and repelled 3T3 cells if their intensity modulation was altered. I found this result in a 22 month long study which established a spectrum of motile responses of 781 individual 3T3 cells and 148 CV1 cells to the near-infrared emissions of microscopic, pulsating light sources using the infrared spot-irradiation phase-contrast (IRSIP) microscopic [Albrecht-Buehler, 1991: J. Cell Biol. 114:493-502]. Thus the response of cultured, mammalian cells to near-infrared light signals is not merely a matter of total energy absorption by cirtain cytoplasmic componets. Since it seems to depend on the cell type and the temporal pattern in which the light energy is emitted, it appears to imply the existence of a new kind of cellular information. © 1995 Wiley-Liss, Inc.
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    Microtubule-associated movement of mitochondria and small particles in Acanthamoeba castellanii (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 32 (1995), S. 305-317 
    Details
    ISSN: 0886-1544
    Keywords: organelle transport ; cytoskeleton ; amoeba ; video microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Using video-enhanced differential interference microscopy and digital image processing, we have observed organelle motility in Acanthamoeba castellanii. In amoebae taken from cultures in rapid growth phase, mitochondria and small particles moved over distances of several microns and at an average velocity of ∼2 μ/s. Mitochondrial motility was verified by intensified fluorescence microscopy of cells that were labeled in vivo with the DNA-binding dye DAPI or the mitochondria-specific dye Mito Tracker. We further studied the role of microtubules (MTs) in the translocation of cell organelles. Double-labelling of fixed cells bules with mitochondrial markers (anti-F1β antibody, Mito Tracker) and cytoskeletal markers (anti-tubulin antibody, rhodamine-phalloidin) demonstrate that the mitochondria colocalize with MTs in the subcortical cell area and are excluded from the F-actin-rich cell cortex. Colchicine treatment resluted in an almost complete depolymerization of MTs and an inhibition of organelle motility. Moreover, we have directly visualized MTs in vivo in flattened amoebae. Mitochondria and small particles moved along the MTs in a bidirectional mode at an average velocity of ∼1 μm/s. We conclude that the observed movement of mitochondria and small particles in Acanthamoeba castellanii mainly occurs via microtubules and associated motor proteins. © 1995 Wiley-Liss, Inc.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970320407
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    Phospholipid membrane-associated brush border myosin-I activity (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 30 (1995), S. 26-37 
    Details
    ISSN: 0886-1544
    Keywords: myosin ; myosin-I ; unconventional myosin ; brush border ; epithelia ; membrane ; phospholipid ; fluorescence microscopy ; actin ; calmodulin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Brush border myosin-I (BBMI) is associated with the membrane of intestinal epithelial cells where it probably plays a structural role. BBMI also has been identified on Golgi-derived vesicles in intestinal epithelial cells where it may translocate vesicles into the brush border. However, the mechanochemical activity of BBMI bound to a phospholipid membrane has not been described. This study reports that phospholipid membrane-associated BBMI displays ATPase activity when bound to phospholipids, but does not move actin filaments when associated with a phospholipid bilayer. BBMI does not bind significantly to brush border membrane lipids, which contain about 16% phosphatidylserine (PS), in either a pelleting or planar membrane assay. Similarly, planar membranes containing 20% PS do not bind a significant amount of BBMI. Increasing the concentration of PS to 40% does result in the binding of BBMI to both vesicles and planar membranes. This binding is enhanced with increased Ca2+ concentrations. BBMI retains its ATPase activity when bound to phospholipid vesicles containing 40% PS. However, BBMI attached to a phospholipid bilayer surface does not move actin filaments, even though the amount of BBMI bound to the lipid surface, as reflected by the number of actin filaments associated with bilayer-bound BBMI, is sufficient to observe motility in control experiments. When membrane fluidity is reduced by adding cholesterol to the membrane lipids containing 40% PS, BBMI still binds to the membrane, but again no actin filament motility is observed. The lack of binding by BBMI to brush border membrane lipids and the absence of membrane-associated BBMI mechanical activity suggest that factors in addition to membrane lipids are necessary for membrane-associated myosin-I motility. © 1995 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970300105
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  • 96
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    Monoclonal anti-dipeptide antibodies cross-react with detyrosinated and glutamylated forms of tubulins (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 30 (1995), S. 171-182 
    Details
    ISSN: 0886-1544
    Keywords: tubulin ; post-translational modification ; glutamylation ; tyrosination ; dipeptide antibodies ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Two monoclonal antibodies, GLU-1 and A1.6, raised against γ-L-glutamyl-L-glutamic acid dipeptide (Glu-Glu) and Ca2+ -dependent ATPase from Paramecium, respectively, recognized the dipeptide Glu-Glu sequence. Whereas the antibodies immunofluorescently stained very few, if any, cytoskeletal fibers in cultured mammalian cells, almost all interphase as well as mitotic spindle microtubules became visible after treatment of cells with carboxypeptidase A. Immunoblot analysis demonstrated intense cross-reaction of the antibodies to the α-tubulin subunit. α-Tubulin isotypes produced as fusion proteins in bacteria were labeled by both the antibodies only when the proteins did not contain a tyrosine residue at the C terminus, indicating that GLU-1 and A1.6 specifically recognize the detyrosinated from of α-tubulin. When microtubule protein purified from brain was probed, not only α-but also, to a lesser extent, β-tubulin were revealed by the dipeptide antibodies. A synthetic tripeptide YED containing one glutamyl group linked to the second residue of the peptide via the γ position was also recognized by the antibodies. Since this peptide sequence corresponds to the amino acid sequence of polyglutamyated class IIIβ isotype at amino acid position 437 to 439, it is suggested that GLU-1 and A1.6 are able to recognize the glutamylated form of β-tubulin. These results indicate that the C-terminal Glu-Glu sequence displays strong antigenicity, and the antibodies recognize the sequence present in the C terminus of the detyrosinated form of α-tubulin and the glutamyl side chain of β-tubulin. Particularly strong immunoreaction was detected with ciliary and flagellar microtubules; thus, stable axonemal microtubules appear to be rich in post-translationally modified tubulin subunits. © 1995 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970300302
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  • 97
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    Myosin heavy chain isoform expression in human myometrium: Presence of an embryonic nonmuscle isoform in leiomyomas and in cultured cells (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 30 (1995), S. 183-193 
    Details
    ISSN: 0886-1544
    Keywords: uterus ; leiomyomas ; cultured smooth muscle cells ; α-smooth muscle actin ; desmin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We had previously found no myosin heavy chain (MHC) changes in expression during pregnancy in human myometrium. In the present work, we compared the MHC pattern of expression in normal human myometrium, pregnant and non-pregnant, to that in benign tumors of the uterine musculature and in cultured myometrial cells. We used a high-resolution gel electrophoretic system and monoclonal antibodies directed against smooth muscle and nonmuscle MHCs. Smooth muscle MHCs (SM1, 204 kDa, and SM2, 200 kDa, MHCs) and a nonmuscle MHC of 196 kDa (NM MHC) were detected in pregnant and nonpregnant human myometrium. Pregnant myometrium was found to differ from nonpregnant myometrium by its slightly lower content in NM MHC, whereas the ration of SM1/SM2 was equivalent. In leiomyomas and in cultured cells grown from human myometrium explants, SM1, SM2, and NM MHCs were also expressed. In addition, a nonmuscle MHC of 198/200 kDa (SMemb MHC), which was present in a fetal human uterus but not in adult normal tissue, was observed in leiomyomas and in cultured cells. Expression of SM1 and SM2 MHCs was variable in the different leiomyomas studied. In cultured cells, SM1 and SM2 MHC content was low, but it was enhanced by suppression of serum after cell confluency. Present results confirm that pregnancy-associated smooth muscle cell hypertrophy is not accompanied by major changes in MHCs. In contrast, cell culturing and cell hyperplasia leading to leiomyoma formation induce substantial modifications in MHCs, including the occurrence of a second type of nonmuscle MHC. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970300303
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  • 98
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    Buckling of a single microtubule by optical trapping forces: Direct measurement of microtubule rigidity (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 30 (1995), S. 221-228 
    Details
    ISSN: 0886-1544
    Keywords: Key words: microtubules, flexural rigidity, optical trapping, microtubule-associated proteins, taxol ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: As major determinants of cell shape and polarity, microtubules are required to have suitable rigidity. However, our knowledge of the mechanical properties of microtubules is far from satisfactory. We report here a new method of measuring the flexural rigidity of a single microtubule by direct buckling using the optical trapping technique. Microtubule buckling was induced by applying a small longitudinal compressing force through an optically trapped microsphere that was firmly attached to the microtubule. Three ways of estimating the flexural rigidity of a continuous slender rod, one from the observed critical load of buckling and two from deflected lengths and angles of bending, yielded values which agreed well when applied to the analysis of buckling microtubules. Unexpectedly, we found that the rigidity was not constant as expected but was dependent on microtubule length. This length dependency explains the discrepancies among reported values of microtubule flexural rigidity measured by different methods. Comparing microtubules of identical lengths, microtubules assembled with brain-derived associated proteins (4 × 10-23 Nm2 at around 10 m̈m in length) were four times more rigid than those assembled from purified tubulin and stabilized with taxol (1 × 10-23 Nm2). © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970300306
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  • 99
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    Identification and molecular characterization of a yeast myosin I (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 30 (1995), S. 73-84 
    Details
    ISSN: 0886-1544
    Keywords: myosin I ; yeast ; SH3 ; proline-rich ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The family of myosin motors is comprised of numerous classes distributed among a diverse set of organisms and cell types. We have identified an unconventional myosin gene (MYO3) in the yeast Saccharomyces cerevisiae and show that it is member of a subclass of unconventional myosin proteins originally found only in the amoeboid organisms Dictyostelium and Acanthamoeba. Identification of this protein in these genetically and morphologically divergent organisms suggests that it will be ubiquitous in eukaryotes and that it has a role in the basic functions of the eukaryotic cell. We have constructed a strain of yeast missing 99% of the MYO3 coding sequence. This mutation has no observable phenotypic effect, placing MYO3 into a growing class of yeast genes which are dispensable under laboratory conditions, perhaps due to genetic redundancy. Alignment of MYO3 with other unconventional myosins shows that it shares with a subset of them a previously unrecognized region of homology in the tail; this region falls within a domain identified as important for mediating nonspecific electrostatic interactions with membranes. The existence of this region suggests that it may be involved in mediating specific protein-protein interactions, possibly helping to localize this myosin to specific membranes or membrane regions. In addition, we show that “classic” myosin I proteins share a region of hyper-proline-richness 10 amino acids before the SH3 domain. Proline-rich regions have recently been implicated as SH3 binding sites, which suggests that this region might be involved with regulating or in other ways interacting with SH3 domains. © 1995 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970300109
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  • 100
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    Focal adhesion proteins associated with apical stress fibers of human fibroblasts (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 31 (1995), S. 177-195 
    Details
    ISSN: 0886-1544
    Keywords: focal adhesion ; stress fiber ; vinculin ; talin ; integrin ; focal adhesion kinase ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Human fibroblasts stained with fluorescently labeled phalloidin revealed many stress fibers within the apical cytoplasm in addition to those located along the basal plasma membrane and associated with focal adhesions. The staining patterns of these apical stress fibers with fluorescent phalloidin, anti-α-actinin, and anti-myosin were identical to those of the basal stress fibers, suggesting the same macromolecular organization for both types f stress fibers. There were two types of apical stress fibers that clearly interacted with the apical plasma membrane, those extending between the basal and the apical plasma membrane and those having both ends on the basal membrane forming arches whose top interacted with the apical plasma membrane. By electron microscopy, we observed that apical stress fibers were associated with the apical plasma membrane via electron-dense plaques reminiscent of the focal adhesion. Since several proteins have been specifically localized to the focal adhesion site, we examined whether they were also present at the apical stress fiber-membrane association site by using immunocy-tochemical methods and image reconstruction techniques. We found that vinculin, talin, paxillin, a fibronectin receptor protein, several integrin subunits including β1, fibronectin, and proteins with phosphorylated tyrosine were also components of the apical plaque. These observations indicate that apical stress fibers are attached to the plasma membrane by using principally the same molecular assembly as the focal adhesion associated with the basal stress fiber. We suggest that the complex molecular organization of the focal adhesion is not demanded by cell adhesion, but rather it is needed for anchoring stress fibers to the plasma membrane. Apical plaques did not stain with the anti-integrin αv subunit or anti-focal adhesion associated kinase (FAK), although these antibodies stained focal adhesions. These results suggest that the apical stress fiber-membrane contact has some important functions different from those of the focal adhesion.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970310302
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