摘要:

Abstract(Z)‐(3,3‐Dimethylbicyclo[2.2.1]hept‐2‐ylidene)methyllithium can be readily generated by treatment of (Z)‐3‐bromomethylene‐2,2‐dimethylbicyclo[2.2.1]heptane withtert‐butyl‐lithium. At ‐75°C, the organometallic intermediate is configurationally stable and reacts with a variety of electrophiles under st

ISSN:0009-2940    

DOI:10.1002/cber.19971300112

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractAlk‐2‐enylpotassium compounds having theendoconformation are synthetically very valuable precursors of (Z)‐olefinic derivatives substituted at the outward allylic position. They may be generated by „stereoconservative’︁ metalation of the readily available (Z)‐alk‐2‐enes by using the superbasic mixture of butyllithium and potassiumtert‐butoxide or by metalation under similar conditions of stereorandom mixtures of alk‐2‐enes or alk‐1‐enes followed by torsional isomerization of the concomitantly formedexoconformers to the thermodynamically more stableendospecies. The principal factors that dictate the rate and the extent of theendo/exoequilibration are the substrate geometry, the solvent, the temperature, the reagent s

ISSN:0009-2940    

DOI:10.1002/cber.19971300113

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractSeveral products resulting from the condensation of the bis‐(trimethylsilyl)ylide1with PCl3serve as synthetic equivalents of a phosphoniophosphaethyne. Cycloaddition reactions with azides lead to phosphonio‐1,2,3,4‐triazaphosphole cations5, 7and to the zwitterionic phosphonio‐1,2,3,4‐triazaphospholide6. The latter readily undergoes a cycloreversion yielding a phosphoranediyl diazomethane12as intermediate. Its cycloaddition affords the diphosphonio‐1,2,4‐diazaphosholide chloride9aas the final product.9ais a remarkably stable and unreactive derivative of the two‐coordinate phosphorus. By HCL it is protonated at a nitrogen atom to give dication without any tendency to associate with the chlor

ISSN:0009-2940    

DOI:10.1002/cber.19971300114

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractA series of isothiazole‐based potential ligands bearing substituents with additional donor sites in the 5‐position of the heterocycle was synthesized [3‐Me‐5‐R‐C3HNS; R = CHN(CH2)2py (1), CHNCH2py (2), CH2N(CH2CH2NEt2)2(4), (CH2)2SMe (5)]. Upon reaction with AgO3SCF3they formed complexes [(1)AgOSO2CF3]2(6), [(2)AgOSO2CF3]2(7), [(4)Ag]2+2(O3SCF−3)2(8) and [(5)AgOSO2CF3]2(9), respectively.6,8and9were shown by X‐ray structural analyses to consist of dimeric units L2Ag2+2, either discrete (8), coordinated by terminal CF3SO−3units (6). In8and9the isothiazole moiety is bonded to the metal center via the ring‐N. The coordination potential of the isothiazole h

ISSN:0009-2940    

DOI:10.1002/cber.19971300115

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe zinc hydroxide complexes Tp*Zn–OH with TpCum,Me= tris(3‐cumenyl‐5‐methylpyrazolyl)borate and TptBu,Me= tris(3‐tert‐butyl‐5‐methylpyrazolyl)borate can be converted to the alkyl carbonate complexes Tp*Zn–OCOOR by reaction with dialkyl dicarbonates or with alcohol and CO2. An alternative formation reaction is the treatment of the pyrazolyl borate with zinc perchlorate and potassium carbonate in alcohol. The interconversion between TpCum,MeZn–OH and TpCum,MeZn–OCOOMe in methanol‐containing solution can be repeatedly performed in both directions by bubbling either CO2or N2through the solution. The alkyl carbonate complexes show a variable sensitivity towards hydrolytic destruction with reformation of the hydroxide complexes. The complexes TptBu,MeZn–OCOOR (R = Me, Et) release CO2under high vacuum to form the alkoxide complexes TptBu,Me‐Zn–OR, which could not be obtained pure due to their extreme water sensitivity. Indirect evidence for their existence is also obtained by the reaction between TpCum,MeZn–OCOOMe and methyl iodide, forming TpCum,MeZn–I and dimethyl ether. The Zinc hydroxide complexes catalyse the formation of dieth

ISSN:0009-2940    

DOI:10.1002/cber.19971300116

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractTriphenylphosphite has been converted into tris(phenylthiomethyl)phosphane (1) by reaction with LiCH2SPh/DABCO, and subsequently into the corresponding sulfide (2) and selenide (3) by treatment with elemental sulfur or selenium, respectively. Ligands2and3react with copper(I) halides CuX (X = Cl, Br, I) in polar organic solvents to give either 1:1 (X = Cl:4,7, X = Br:5,8) or 1:2 complexes (X = Br:9, X = I:6,10). The crystal structures of five of these complexes have been determined by single crystal X‐ray diffraction studies. All compounds of the type [(PhSCH2)3PS/Se]CuX (X = Cl, Br) form centrosymmetrical dinuclear complexes featuring a four‐membered ring core Cu2[S/Se], fused to two five‐membered rings Cu[S/Se]PCS through common trans edges. Only one of the three phenyl‐thiomethyl functions is involved in coordination to a metal center. The compound [(PhSCH2)3PS](CuI)2(6) is associated into a centrosymmetrical tetranuclear complex containing two four‐membered rings (ICu2S) bridged via iodine atoms in 1,3‐cispositions. The ligand is found to employ two of its PhSCH2functions for metal coordination, giving rise to two five‐membered rings fused to the four‐membered rings via neighbouring edges. In all cases, therefore, the PS/Se functions of the ligands are the preferred donor sites, which are used for the building of bridgehead structural units of

ISSN:0009-2940    

DOI:10.1002/cber.19971300117

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractA new synthetic route to the bis(tetrafluoroborate) salt of the hexakis[(triphenylphosphane)gold(I)]methanium dication has been opened up through the reaction of trimethylsilyldiazomethane and tris[(triphenylphosphane)gold(I)]oxonium tetrafluoroborate in dichloromethane. Yields are close to 65% if the reaction is carried out in the presence of triethylamine as a base. The process is a sequence of desilylation, deprotonation and deazotation reactions at the carbon function of the diazomethane, as shown by the detection of intermediates. The crystal structure of the title compound (with three equivalents of crystal dichloromethane) has been determined in a single‐crystal X‐ray study. The dication has no crystallographically imposed symmetry, but the core is a distorted, carbon‐centered octahedron of gold atoms. This result confirms the data from previous structural studies of salts with other anions and interstitial sol

ISSN:0009-2940    

DOI:10.1002/cber.19971300118

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractReactions of (R3P)AuX (X = Cl, Br, I) with [(R3P)Au]+BF−4obtained from (R3P)AuCl and AgBF4in tetrahydrofuran, lead to cationic binuclear gold(I) complexes of the general formula ([(R3P)Au]2X}+BF−4. A number of chloro‐ (R = Ph,o‐Tol, Mes, Bzl, Et), bromo‐ (R = Ph,o‐Tol, Mes) and iodo‐bridged (R = Ph, Mes) complexes of this type have been isolated and identified on the basis of their analytical and spectroscopic data. The crystal structure of bis[(triphenylphosphane)gold(I)]bromonium tetrafluoroborate was determined by single‐crystal X‐ray diffraction. The cations contain two‐coordinate bromine atoms with an Au‐Br

ISSN:0009-2940    

DOI:10.1002/cber.19971300119

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractLithium 2,2,6,6‐tetramethylpiperidide inserts elemental selenium into its Li–N bond with the formation of lithium 2,2,6,6‐tetramethylpiperidinoselenolate1. In the crystal1is an unsymmetric dimer. One lithium atom is coordinated tetrahedrally by two molecules of tetrahydrofuran and two selenium atoms, the other lithium atom exhibits an approximately rectangular‐planar coordination by two N,Se‐chelating groups. The lithium atoms are bridged by two selenium atoms thus forming a planar Li2Se2core. Ab initio Hartree‐Fock calculations show1and the hypothetical symmetric dimer2to be of equal energy, whereas the non‐chelated dimer3is of distinctly higher energy. Exclusive crystallization of1is most likely a consequence of its large dipole moment of 6.18 D. Calculations also show that the deformation of the observed geometry around the uniquely coordinated lithium atom in1towards distorted tetrahedral or complete planarity leads to an increase of energy. Excessive charge transfer from selenium to nitrogen explains the overwhelming tendency for the N,Se‐ch

ISSN:0009-2940    

DOI:10.1002/cber.19971300120

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractChiral or achiral (arene)(COD)Ru complexes can be made by replacing the η6‐ligands of (η4‐1,5‐COD)(η6‐1,3,5‐cyclooctatriene)Ru (1) or (η4‐1,5‐COD)(η6‐naphthalene)Ru (2) by a suitable arene. This well known reaction has been extended to mono‐ and dibromoarenes and we report a novel route to substituted (arene)(COD)Ru species, utilizing (bromoarene)‐(COD)Ru as starting materials. These facilitate a rapid bromine‐lithium exchange reaction withnBuLi at low temperatures and the lithiated species react readily with alkyl chloroformates as electrophiles. By using chiral electrophiles [alkyl = (‐)‐menthyl] enantiomerically pure or diastereomeric complexes containing CO2R*groups are formed, depending on the symmetry of the original complex. A diastereomeric 1:1 mixture was separated by recrystallization. All (arene)‐(COD)Ru complexes tested so far are useful as catalysts for the hydrogenation of si

ISSN:0009-2940    

DOI:10.1002/cber.19971300121

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY