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  • Wiley-Blackwell  (38)
  • 1990-1994  (38)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 171-181 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conversion of the conformation of cyclosporin A (CsA) observed in CHCl3 to the receptor-bound state is investigated by two molecular-mechanics methods, template forcing and dynamic forcing. The conformations of CsA in CHCl3 and complexed with LiCl in THF as determined by NMR are used as starting structures. The transition starting from the CsA/CHCl3-derived conformation is hindered by steric interactions of two side chains (MeBmt1 and Val5). While starting with the CsA/LiCl-derived conformation, the conversion is facile. It is illustrated that these calculations, which are of artificial character, using only the starting and final structures of the observed conformational transition during the receptor-binding event, allow an insight into the interactions between the substrates and receptor in terms of an induced fit.
    Additional Material: 6 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 1001-1004 
    ISSN: 0009-2940
    Keywords: Amino acid complexes ; L-Glutamate complexes ; Hydrogen L-glutamate complexes ; Potassium hydrogen L-glutamate ; Hydrogen bonding ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compound is obtained by neutralization of aqueous solutions of L-glutamic acid with potassium hydroxide, and crystallization from aqueous methanol. The compound shows a pH of 7 in water at ambient temperature and an optical rotation [α]20D of -4.30 (c = 3.0). In the crystal (orthorhombic, space group P212121) the potassium ion is in a distorted trigonal-prismatic environment of six oxygen atoms of four different amino acids and of the water molecule. No nitrogen coordination is observed. Through the bridging function of some of the α-carboxylate oxygen atoms (O1, O2) and through complexation of the metal through the γ-carboxylate groups (O3), a layer-coordination polymer, with strings of potassium ions running parallel, is formed. The layers are cross-linked by hydrogen bonds involving the ammonium and γ-carboxylate functions as well as the water molecule.
    Additional Material: 3 Ill.
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  • 3
    ISSN: 0009-2940
    Keywords: Gold(I) complex ; Phosphine (selenide) complexes ; Aus···Au interactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [(CO)AuCl] reacts with equimolar amounts of Ph2PCH2P(Se)Ph2 (dpmSe) to afford ClAuPh2PCH2P(Se)Ph2, in which dpmSe is bound to gold in a monodentate fashion by phosphorus. Subsequent reaction of this 1:1 complex with AgClO4 results in the formation of the 10-membered ring complex 4 which crystallizes in the monoclinic space group P21/n with approximately centrosymmetric dicationic units, in which two gold (I) atoms are doubly bridged by two dpmSe ligands coordinated by phosphorus and selenium. The coordination at the gold atoms deviates from linearity and implies an Au···Au interaction with the gold(I) atoms separated by a distance of 3.020(1) Å.
    Additional Material: 2 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 1017-1023 
    ISSN: 0009-2940
    Keywords: Borates, triorgano-oxy, potassium salts ; N-Lewis base - diorgano(silyloxy)boranes ; Bicyclo[2.2.1]heptanes, heteroatom-containing, diastereomeric ; P-Lewis base - triorganoboranes, monocyclic, unsaturated ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: OrganosubstitutedBicyclic and Monocyclic Compounds from 2,5-Dihydro-1,2,5-oxasilaboratolates1a)The potassium salts of the cyclic anions of (A: R, R′ = CH3; B: R = C2H5, R′ = CH3; C: R = C6H5, R′ = CH3 react with [(CH3)2NCH2]Br in THF to yield the bicyclic compounds 1a (X-ray crystal structure analysis), 1b/1b' (endo/exo-C2H5), and 1c/1c' (endo/exo-C6H5). D (R=CH3, R'=C6H5) reacts with [(CH)32NCH2]Br to form a 1:4 mixture of 1d together with the heterocycle (3d) with elimination of (CH3)2N-C3H7. - From A - D and CIP(C6H5)2 the six-membered heterocycles (2a-d) are obtained in yields of ca. 90%.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 285-287 
    ISSN: 0009-2940
    Keywords: Phosphanes, primary / Gold complexes / Gold-gold interactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (CO)AuCl reacts with (2,4,6-trialkylphenyl)phosphanes 1a-d (alkyl = Me, Et, iPr, tBu) to give the 1:1 complexes 2a-d. The crystal structure of 2d shows pairs of molecules with Au…Au contacts of 3.440(1) Å.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 1525-1530 
    ISSN: 0009-2940
    Keywords: 1,3-Diphosphabenzene derivatives ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses, NMR spectra, and X-ray molecular structures of three (2-hetero-)1,3-diphosphabenzenes are reported which constitute an isoelectronic triade of compounds with BH2, CH, and N bridging units between the two phosphorus atoms. The remaining three carbon atoms of the rings are part of a 2-methallylic system. The 2-borataheterocycle 3 has been prepared by the reaction of CH2 = C(CH2)PPh2)2 (1) with Me2S—BH2Br to give an intermediate 2 still containing the exocyclic olefinic bond. Treatment of 2 with a base, deprotonation of one ring CH2 group, and proton migration from the other one to the olefinic CH2 group afford the 5-methyl-1λ5-phospha-3-phosphonia-2-boratabenzene 3. The PBP unit is tilted by 144.0(2)° against the planar C3P2 part of the ring. A heterocyclic precursor 4 for the carbon analog is generated from 1 and CH2I2, which on reaction with a strong base yields the diphosphabenzene 5 with a fully planar ring skeleton. For the synthesis of the aza analog 7, CH2=C(CH2Cl)2 is treated with HN(PPh2)2 to give the precursor 6, which can be deprotonatad at nitrogen and carbon with a base. In the crystals of 7, two independent molecules of very similar structure are present. The molecules show planar heterocycles.
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  • 7
    ISSN: 0009-2940
    Keywords: Ferrocenes ; Cyclopentadienes, disilyl- ; Silatropic rearrangement ; Lithium cyclopentadienides ; Metallocene, trinuclear, mixed-metal ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The tetrahydro-4,4,8,8-tetramethyl-4,8-disila-s-indacenyl anion (LH) reacts with or without cyclopentadienyl anion (Cp-) and Fe2Cl4(THF)3 to give the mixed ferrocenes CpFe(LH) and (LH)2Fe in 50 and 63% yield, respectively. Near room temperature and in solution CpFe(LH) exists as a pair of enantiomers (syn-3a/b). According to an X-ray analysis both enantiomers are present in a single crystal. Compound 3 consists of a ferrocene linked to a cyclopentadiene by two Me2Si groups such that the acidic Cp proton points towards the iron. Temperature-dependent NMR spectra show that syn-3a and syn-3b are non-rigid molecules which are interconverted by 1,2-silatropic bond shifts (Ea = 49.2 ± 2.9 kJmol-1). Three more isomers (anti-3a, anti-3b, and the spiro derivative 3c), though present only in low concentration, are engaged in the rearrangement. (LH)2Fe is also non-rigid and exists as a pair of diastereomers (4a and 4b). The isomers of 3 and 4 undergo hydrolysis (e.g., syn-3a/3b gives [(Me2SiOSiMe2)Cp]FeCp (5) among others) and deprotonation. The latter yields CpFe(L-) (7) and (L-)2Fe (8), which are characterized by NMR spectroscopy. 7 forms crystals with [Li(TMEDA)]+ as counterion, and an X-ray analysis shows that lithium and iron are located at opposite sides of the strongly folded ligand L. The reaction of 7 with CrCl2(THF) gives the trinuclear stacked metallocene 9 in 47% yield. 9 has two unpaired electrons which are located essentially in the center of the molecule.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 1221-1226 
    ISSN: 0009-2940
    Keywords: π-Complexes of p-block elements ; Arene complexes ; Arsenic complexes ; Antimony complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,2,4,5-Tetramethyl-and pentamethylbenzene from stable 1:2 complexes with SbCl3 of the type (C6H6-Men) · 2SbCl3(1,2) with an inverse sandwich structure. The compounds crystallize isotypically and are isostructural to the (hexamethylbenzene)antimony and -bismuth complexes.They are thus built of tetrameric chlorine-bridged Sb4Cl12 units, which are crosslinked at the metal centers with four other tetramers by double-sided arene coordination (X-ray structure analysis of 1). The Sb atoms, which are in a distorted trigonal bipyramidal environment, show a slight deviation from a centric (η6) coordination. The same stoichiometry and the same structural principle are found for the complex (C6Me6 · 2 AsCl3 (4), which is obtained from solutions of hexamethylbenzene and AsCl3 in toluene. In 4 the arsenic atoms are η6-coordinated to the hexamethylbenzene ring from both sides (X-ray analysis). Treatment of AsBr3 with hexamethylbenzene leads to a product of the composition 5 (C6Me6) · AsBr3. Reaction of hexaethylbenzene with AsCl3 in petroleum ether leads to the formation of the 1:2 complex (C6Et6) · 2 AsCl3 (5), built of discrete inverse sandwich units, which are arranged in strings parallel to the crystallographic c axis. From solutions of AsCl3 (AsBr3), SbCl3 (SbBr3) and hexaethylbenzene in petroleum ether ternary compounds are isolated with an As:Sb ratio of 1:5.2 and 1:1.86, respectively. Single crystal X-ray structure determinations failed as a consequence of severe disorder.
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  • 9
    ISSN: 0009-2940
    Keywords: Dihydroanthracene ; Dihydroanthracene, butyl-substituted ; Tricarbonylchromium ; Chromium complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The complexes [9,10-dihydroanthracene][tricarbonylchromium]n [9,10-DHA][Cr(CO)3]n [n = 1 (1), 2 (2)] and the related mono- and bis(tricarbonylchromium) complexes of 2,6- and 2,7-di-tert-butyl-9,10-dihydroanthrancene [2,6-DB-9,10-DHA][Cr(CO)3]n [n = 1 (3), 2 (4)] and [2,7-DB-9,10-DHA][Cr(CO)3]n [n = 1 (5), 2 (6)] have been prepared by heating the 9,10-DHA species in the presence of hexacarbonylchromium [Cr(CO)6]. Evidence for the existence of the complex [2,6,9-tri-tert-butyl-9,10-DHA][Cr(CO)3] (7) is also presented. The complexes have been characterised spectroscopically, and for complex 1 an X-ray crystallographic structure determination has been carried out. This complex adopts the unexpected structure in which the non-coordinated arene ring is bent towards the Cr(CO)3 moiety. The syntheses and spectroscopic characterisations of 2,6- and 2,7-di-tert-butylanthracene (2,6- and 2,7-DBA), 2,6- and 2,7-di-tert-butyl-9,10-dihydroanthracene (2,6-and 2,7-DB-9,10-DHA), 2,6,9-, 2,7,9-, and 2,7,10-tri-tert-butyl-9,10-dihydroanthracene (2,6,9-, 2,7,9- and 2,7,10-TB-9,10-DHA), and 2,6,9,10- and 2,7,9,10-tetra-tert-butyl-9,10-dihydroanthracene(2,6,9,10- and 2,7,9,10-TeB-9,10-DHA) are also given.
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  • 10
    ISSN: 0009-2940
    Keywords: Germanium(II) complexes ; Electron pair, „inert“ ; Spiro compounds ; Molecular fluctionality ; Phosphanylmethanide ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ring Expansion of Spirocyclic Germanium(II) Di(phosphanyl)methanide Complexes by Insertion of Sulfur and Selenium into Germanium-Phosphorus BondsGermanium in the intermolecularly stabilized germylene derivative Ge[C(PMe2)2(SiMe3)]2 (2a) is not oxidized by sulfur but the latter inserts 1 to 4 chalcogenide atoms into the Ge-P bonds of the four-membered chelate (4/4-) rings to give 4/5-, 5/5-, 5/6, and 6/6-membered spirocycles Ge[C2(SPMe2)n(PMe2)4-n(SiMe3)2] (n = 1-4: 4, 5a, 6, 7). Only 5a and 7 could be obtained in pure form, whereas compounds 4 and 6 with odd-numbered chalcogenide atoms are only characterized in solution, where they exist in equilibrium with 2a and 5a or 5a and 7, respectively. All these molecules are fluctional in solution. 7 is also obtained from GeCl2 · dioxane and Li[C(SPMe2)2(SiMe3)]. The selenium compound Ge[C(SePMe2)(PMe2)(SiMe3)]2 (5b) is obtained from 2a and grey selenium in toluene. An X-ray structure determination of 5b shows a distorted sphenoidal arrangement [approximate C2 symmetry of a spirocyclic germanium center within two five-membered rings containing a nearly linear Se-Ge-Se unit (Ge-Se 2.712/2.769(1) Å)]. The angle PGeP is 95.9(1)°. A bonding model with a stereochemically non-active electron lone pair at the formal germanium(II) center may account for this geometry. As byproducts in the sulfurization reactions, bis-(phosphanyl)methane disulfides are also observed in certain cases, from which H2C(SPMe2)2 has been isolated in pure form and characterized structurally.
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