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  • 1
    Electronic Resource
    Electronic Resource
    Nickel Chelate Complexes of 2-Alkylphenylphosphanylphenolates: Synthesis, Structural Investigation and Use in Ethylene Polymerization (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 299-305 
    Details
    ISSN: 1434-1948
    Keywords: Phosphanylphenolate ; Cyclopentadienylnickel complexes ; Chelates ; Ethylene polymerization ; Crystal structure ; Polymerizations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2-Diphenylphosphanyl- and 2-alkylphenylphosphanyl-4-methylphenols 1 or their silyl ethers 2 and equimolar amounts of nickelocene react in benzene preferably to give orange-brown diamagnetic cyclopentadienylnickel chelate complexes [η-CpNi(P∩O)] (3). Addition of a second equivalent of 1 or 2 affords (RR) and (SS) diastereoisomers of cis-bis(P∩O-chelates) 4a-c (R = Ph, Me, iPr) or the unsymmetrical cis-bis(P∩O-chelate) 5, whereas with bulkier substituted derivatives 1d or 2d (R = tBu) the second step is hindered or retarded. The reactivity of 1d remains high towards nickel salts in polar solvents, but in contrast to 1a-c, yielding 4, a sparingly soluble green trans-bis(P-O-chelate) nickel complex 6d is formed. Complexes formed in situ from 1 or 2 and Ni(COD)2 in toluene catalyze the polymerization of ethylene. The cyclopentadienyl (P∩O) complexes 3, however, are too stable to be active in this process. The crystal and molecular structure of 3c and 4c are described.Supporting information for this article is available on the WWW under -//_/_http://www.wiley-vch.de/contents/jc_2005/2000/99035_s.pdf or from the author.
    Additional Material: 2 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    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.
    Additional Material: 5 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    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.
    Additional Material: 9 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    λ5-Phosphetes, Benzo-λ5-Phosphetes, Naphtho-λ5-Phosphetes: Four-π-, Eight-π-, and Twelve-π-Electron SystemsDedicated to Professor Manfred Regitz on the occasion of his 60th birthday (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 68-74 
    Details
    ISSN: 0947-6539
    Keywords: ab initio calculations ; cyclic ylides ; heterocycles ; phosphorus ylides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A number of possible strategies for the preparation of λ5-phosphetes were tested as follows: cyclopropenium 6 was treated with the lithium salt of diphenylphosphine to give phosphinocyclopropene 7, but 7 did not undergo ring expansion upon photolysis or thermolysis. P-chloro-C—trimethylsilyl-substituted ylide 8b reacted with two equivalents of dimethyl acetylenedicarboxylate to afford phosphinine 13 via a transient λ5-phosphete 12. Addition of aluminum trichloride to P-halogenated ylides 17a-b led to dihydrophosphetium salts 19a-b, which, upon treatment with pyridine, isomerized into the 1, 2-dihydrophosphet-2-ium salts 20a-b. Hydrolysis of derivatives 20a-b cleanly afforded phosphoniums 21 a-b, which reacted with NaN(SiMe3)2 to give rise to the corresponding λ5-phosphetes 22a-b. The benzo-λ5-phosphete 22a underwent ring expansion reactions with dimethyl acetylenedicarboxylate and acetonitrile, leading to benzo-λ5-phosphinine and benzo-1, 4λ5-azaphosphinine in good yields. Derivative 22b was characterized by X-ray crystal structure analysis. Ab initio SCF calculations, IGLO-13C chemical shifts and Δχ for various benzannulated derivatives and phosphorus heterocycles are presented.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19960020113
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  • 5
    Electronic Resource
    Electronic Resource
    Centropentaindan, a Fenestrane Bearing Five Mutually Fused Indan Units: Syntheses, Molecular Structure, and Bridgehead SubstitutionBenzoannelated Centropolyquinanes, Part 20; for Part 19, see ref. [8a], for Part 21, see ref. [7]. (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 58-67 
    Details
    ISSN: 0947-6539
    Keywords: centropolyindans ; cyclodehydrogenation ; fenestranes ; polycycles ; triquinacenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses, properties, and some reactions of a novel centropolycyclic hydrocarbon, centropentaindan (1), are described. The molecular structure of 1 consists of a tetrabenzo[5.5.5.5]fenestrane bearing a fifth centrically fused indan unit. Independent syntheses have been developed employing i) twofold cyclodehydrogenation of tribenzotriquinacene (7) with Pd/C at 500°C, which gives 1 in 50% yield, and ii) a two-step procedure by tetrabromination of di-fuso-centrotriindan (8) followed by condensation with two molecules of benzene, which provides 1 in 88% yield. Some bridgehead-substituted centropentaindans are described, including the highly labile dibromo derivative 19, and the centrohexacyclic, topologically nonplanar endo-peroxide 26 and endo-disulfide 28. The notably rigid ring fusion in the molecular framework of 1 is shown both by X-ray structural analysis and by particular steric interactions of the two mutually compressed bridgehead substituents.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19960020112
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  • 6
    Electronic Resource
    Electronic Resource
    Quantum-Chemical Investigations of Stabilizing Interactions in μ-Diborylcarbene Dicobalt Complexes with a Planar Tetracoordinate Carbon AtomDedicated to Professor Gerhard Herberich on the occasion of his 60th birthday (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 294-299 
    Details
    ISSN: 0947-6539
    Keywords: ab initio calculations ; cobalt ; planar carbon ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Quantum-chemical methods have been employed to study the nature of stabilization in dinuclear cobalt complexes of the general formula [{(C5H5)Co}2(μ-CR12BCBR2R3)] (6) as well as the “antivan't Hoff-Le Bel” configuration of the planar tetracoordinate carbon (ptC) atom of the bridging diborylcarbene ligand 9. Extended Hückel and ab initio Hartree-Fock calculations have been carried out for the model compounds 6b (R1 = R2 = R3 = H) and 6c (R1 = R2 = H; R3 = C6H5). Ab initio electron deformation density maps and natural population analysis calculations show that complexes 6 are stabilized through push-pull effects by which the ptC experiences π electron density delocalization and σ electron density accumulation. The calculated electronic configuration of the ptC in the free ligand 9b is σ2.978π1.501, and in 6b σ3.944π1.356. Electron density donation from one cobalt atom to an aryl group on the bridging ligand further contributes to the stabilization of the complexes 6.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030219
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  • 7
    Electronic Resource
    Electronic Resource
    Electron-poor 2,3-Dihydro-1,3-Diborolyl Complexes of Iron and Ruthenium: Synthesis, Reactivity, and Crystal and Electronic Structures of an Iron Sandwich ComplexDedicated to Professor Herbert Schumann on the occasion of his 60th birthday (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 487-494 
    Details
    ISSN: 0947-6539
    Keywords: boron compounds ; diboroles ; Group 8 complexes ; sandwich complexes ; semi-empirical calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The addition product of sodium hydride and the 2,3-dihydro-1,3-diborole (CiPr)2(BEt)2CHMe (3c) reacted with [{(C5Me5)FeCl}x] to produce the green sandwich complex [(C5Me5)Fe{n5-(CiPr)2(BEt)2CMe}] (2 c), which formally contains 16 valence electrons (VE). Complex 2c has unexpected structural properties in the solid state: the 1,3-diborolyl ring is extremely folded (41°), and the Fe-C2 distance is short (1.90 Å). Analogously, violet Ru complexes 4a,c,d were obtained from 3a,c, NaH or tBuLi, and [{(C5Me5)RuCl}4]. With the less bulky heterocycles 3 b,e the new 30 VE triple-decker complexes [(C5Me5)Ru{μ,n5-(CR1)2(BR2)2CMe}RuH(C5Me5)] (5b,e) were formed, which contain a Ru-H bond. Cyclic voltammetric studies revealed the existence of stable anions 2c- and 4d- formed by reversible one-electron reduction at -1.26 and -1.40 V, respectively (vs. SCE). The red-brown anions were further characterized by ESR spectroscopy following stepwise reduction of the neutral species with potassium in THF. Addition of CO to 4a and 4d led to formation of the monocarbonyl complexes [(C5Me5)Ru(CO){n5-(CR1)2-(BR2)2CMe}] (6a,d), and 6d was characterized by X-ray structure analysis. The heterocycle in 6d is less folded (19°) than in 2 c. Its CO ligand causes a 28.5° tilt of the cyclic ligands. Reaction of CO with 2 c yielded a red product of unknown structure. The electronic structure of 2 was studied by EH-MO theory, which revealed a unique bonding in the sandwich. The s̰ electron density of the B-C bonds participates in the bonding to the iron atom; this demonstrates that the number of bonding electrons is the same as in ferrocene. Thus, the complexes 2 actually have 18 VE.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19960020506
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  • 8
    Electronic Resource
    Electronic Resource
    A Novel Type of Resonance-Stabilised Dicobalt Complex with a Cyclopentadienylidene Bridge - Synthesis, Structure and Electronic Properties of [(C5R5)Co(μ-C5H4)Co(L)(C5R5)'] (L = C2H4, CO, CNtBu, PR3, P(OMe)3; R = H, Me) (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 1453-1465 
    Details
    ISSN: 0947-6539
    Keywords: carbenes ; CH activation ; dinuclear complexes ; sandwich complexes ; spin equilibria ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dinuclear μ-cyclopentadienylidene complexes [(C5R5)Co(μ-C5H4)-Co(C2H4)(C5R'5)] (5) [5aa (R = R' = H), 5ab (R = H, R' = Me), 5ac (R = H, R'5 = H4Me), 5ba (R = Me, R' = H), 5bb (R = R' = Me) and 5da (R5 = Me4Et, R' = H)] were synthesised from [(C5R5)Co(η4-C5H6)] (4) [4a (R = H), 4b (R = Me), 4d (R5 = Me4Et)] and [(C5R'5)Co(C2H4)2] (1) [1a (R' = H), 1b (R' = Me) and 1c (R'5 = H4Me)]. In these reactions, both CH bonds of the methylene group of coordinated cyclopentadiene are activated under mild conditions. Substitution of the ethylene ligand in 5 by L leads to the carbonyl, isocyanide, phosphine, and phosphite derivatives [(C5R5)Co(μ-C5H4)Co(L)-(C5R'5)] [6aa, 6ab, 6ba, 6bb (L = CO), 7aa (L = tBuNC), 8aa, 8ab (L = PMe3), 9aa (L = PMe2Ph), 10aa (L = PMePh2) and 11aa (L = P(OMe)3)]. The crystal structures of 5aa, 5ab, 5ba, 6aa and 8aa have been determined. The experimental geometry is rationalised in terms of two limiting structures with μ-η4:η1 and μ-η5:η1 coordination of the bridging cyclopentadienylidene ligand. On the basis of the 18 valence electron rule, zwitterionic character is assigned to latter. This structure is preferred when L is an acceptor ligand, as in 6. In solution, 5-11 are fluxional with rapid rotation about the very short cobalt-carbene C bond. In addition the hindered rotation of the ethylene ligand in 5ab was studied by DNMR spectroscopy. In solution, a singlet-triplet equilibrium was established by variable-temperature NMR spectroscopy for 8aa. The temperature-dependent 1H NMR line shifts were analysed by means of an isotropic shift model to give 24≤ΔH° ≤ 32 kJ mol-1 and 45≤ΔS° ≤74 J mol-1 K-1 with the triplet state being preferred by entropy at higher temperatures.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19960021119
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  • 9
    Electronic Resource
    Electronic Resource
    Through-Bond Interactions in Silicon-Phosphorus and Silicon-Arsenic Compounds: A Facile Synthesis of Dodecamethyl-2,3,5,6,7,8-hexasila-1λ3,4λ3-diphosphabicyclo[2.2.2]octane, Its Arsenic Analogue, and Related Compounds (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 874-880 
    Details
    ISSN: 0947-6539
    Keywords: ab initio calculations ; arsenic ; silicon ; phosphorus ; photoelectron spectroscopy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dodecamethyl-2,3,5,6,7,8-hexa-sila-lλ3,4λ3-diphosphabicyclo[2.2.2]oc-tane (1) and its arsenic analogue 2 are readily accessible in 69 and 73% yield, respectively, by the cyclocondensation reaction of 1,2-dichloro-1,1,2,2-tetrame-thyldisilane (5) with the lithium pnictides [LiEH2(dme)] (E = P (6), As(7); dme = 1,2-dimethoxyethane). The reactions proceed via 1,4-diphosphaoctamethyltetrasi-lacyclohexane (8) and its arsenic analogue 9, respectively, which were isolated and structurally characterized by X-ray crystallography. The molecular structures of 1 and 2, which are isotypic, were also established by single-crystal X-ray analysis: they possess D3 point symmetry with the expected Si-E bond lengths (E = P, As) but unusually long Si-Si bonds. The latter are 0.02-0.03 Å longer than those in 8 and 9, mainly due to through-bond interactions (TB) between donating n orbitals of the E atoms and the σ* acceptor orbitals of the Si-Si bond. The first expanded analogues of 1, namely, 12 and 14, with hexamethyltrisilane and dodecamethyl-hexasilane chains bridging the two phosphorus atoms, were synthesized in a onepot cyclocondensation reaction of the corresponding 1,3- and 1,6-dichloro-oligosilanes 11 and 13, respectively, with [LiPH2(dme)]6. Ab initio calculations on the parent compounds 1a, 12a, and the second-row analogue 1,4-diazabicyclo-[2.2.2]octane (B) were carried out in order to analyze the different coupling constants and magnitudes of intramolecular interactions (through-space/through-bond coupling). TS and TB coupling in B were found to be about two times stronger than in the congener 1a, due to the compactness of the N2C6 skeleton and the greater extent of s, p hybridization at nitrogen. Evidence for TB interactions in 1 was obtained by photoelectron spectroscopy and by comparison of the two first vertical ionization potentials with calculated values for 1a. The best agreement with experimental data was achieved when 1a was calculated at the MP2 level. Compound 1a preferentially adopts D3 point symmetry; the higher-symmetry D3h form possesses one imaginary frequency and is slightly less stable (0.46 kcal mol-1 at HF/6-31 G*//HF/6-31 G* and 1.58 kcal mol-1 at MP2/ 6-31 G*//HF/6-31 G* level), suggesting that this structure corresponds to a transition state on the potential energy surface. The structures corresponding to the global minimum of B and 12a have D3h and C3h symmetry, respectively. At the HF/6-31 G*//HF/6-31 G* level the D3h form of 12a is 17.61 kcal mol-1 less stable than the C3h minimum.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030607
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  • 10
    Electronic Resource
    Electronic Resource
    Carbon Monoxide and Isonitrile Insertion into the B-B Bond of Five-Membered Cyclic Organo-1,2-diboranes (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 459-463 
    Details
    ISSN: 1434-1948
    Keywords: 1,2-Diboraheterocycles ; Carbon monoxide insertion ; Isonitrile insertion ; Dimerisation ; Spiro insertion products ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The insertion of CO into the B-B bond of 1,2-bis(diisopropylamino)-2,5-dihydro-1H-1,2-diborole (1b) and 1,2-bis(diisopropylamino)-3-methylidene-1,2-diborolane (1c) leads to the dimeric spiro products 1,7,9,14-tetrakis(diisopropylamino)-6,13-dioxa-1,7,9,14-tetraboradispiro[4.2.4.2]tetradeca-2,10-diene (4b) and 1,7,9,14-tetrakis(diisopropylamino)bismethylidene-6,13-dioxa-1,7,9,14-tetraboradispiro[4.2.4.2]tetradecane (4c). Insertions of CO into the B-B bonds of the cyclic organo-1,2-diborane compounds 5, 6, and 7 are not observed. The reaction of 1b with tert-butyl isocyanide and 2,6-dimethylphenyl isocyanide in THF leads to the formation of the monomeric insertion products 1,3-bis(diisopropylamino)-2-tert-butylimino-1,3-diboracyclohex-4-ene (10b) and 1,3-bis-(diisopropylamino)-2-(2′,6′-dimethylphenylimino)-1,3-diboracyclohex-4-ene (11b). The treatment of 1cwith the isonitriles yields 2-tert-butylimino-1,3-bis(diisopropylamino)-4-methylidene-1,3-diboracyclohexane (10c) and 1,3-bis(diisopropylamino)-2-(2′,6′-dimethylphenylimino)-4-methylidene-1,3-diboracyclohexane (11c). The steric requirements of the isonitrile insertion products 10b, c and 11b, c prevent their dimerisation and rearrangement. 11b rearranges to 1-(diisopropylamino)-2-(diisopropylaminohydroxyboryl)-2-(2′,6′-dimethylphenylamino)-1-boracyclopent-3-ene (12b) upon reaction with water from sodium sulfate decahydrate. The compositions of the compounds are derived from the 1H-, 11B-, 13C-NMR data as well as from mass-spectral and C, H, N analyses. In the cases of of 4b and 12b they have been proven by X-ray structure analyses.
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