摘要:

AbstractPalladium complexes L2PdX2containing various group Va ligands and weakly coordinating anions are active catalysts for the carbonylation of olefin substrates. These catalytic systems, though gaining significance in industry for the synthesis of polyketones, are normally characterised by a low chemoselectivity. This derives from the numerous possibilities for initiation and termination reactions which lead to different catalytic cycles and from facile multiple alternating insertion reactions of olefins and carbon monoxide. Based on experiments carried out under conditions of low selectivity and on previously published data, the factors involved in the control of the regio‐, chemo‐ and stereoselectivity for those reactions are discussed, taking current ideas and model studies involving the above palladium complexes into considerat

ISSN:0009-2940    

DOI:10.1002/cber.19971301103

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractPalladacycles are discussed as the key intermediates of some important preparative ring forming reactions; their reactivity depends strongly on the ring size. The existence of 5‐membered palladacycles, and even 4‐membered palladacycles, is now firmly established, whereas the knowledge of 6‐membered and larger palladacycles is based mainly on mechanistic considerations. The role of 5‐membered palladacycles as catalysts is described

ISSN:0009-2940    

DOI:10.1002/cber.19971301104

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe reaction between aryl azides and lithiated aryl amines leads to tetrazenes3and9which contain a chain of four nitrogen atoms. Reaction with different halosilanes gives the cyclic silatetrazenes10,12, and15where substitutents on the silicon vary form alkyl to hydrogen and chlorine atoms. The structures of10,12, and15in the solid state are reported. Variation of the solvent and the Lewis acidity of the halosilane influence the ratio of silatetrazene to side products, bissilyated amines. These effects are studied for different halosilanes.

ISSN:0009-2940    

DOI:10.1002/cber.19971301105

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractCobalt(II) 2,9,16,23‐tetrasulphophthalocyanine and cobalt(II) 2,9,16,23‐tetra(chlorosulphonyl)phthalocyanine were supported on TiO2by reaction of the phthalocyanines with Ti(OR)4followed by sol‐gel synthesis. The thus obtained solid materials are stable in sulfide‐containing media and are therefore suitable as catalysts for HS oxidation. The structure of the samples was characterized by electron microscopy diffraction. The morphology of the matrix strongly depends on the cobalt phthalocyanine derivative. The pathalocyanines in the titania matrices are monomeric or dimeric depending both on the type of substituents of the CoPc derivative and on the titanium alkoxide used as pre

ISSN:0009-2940    

DOI:10.1002/cber.19971301106

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractEtheneiridium(I) complexes of the general compositiontrans‐[IrCl(C2H4)L2] [L =iPr2PCH2CO2Me (2a), iPr2PCH2CO2Et (2b),iPr2P(CH2)3NMe2(2c)] have been prepared either from [IrClL2] (3) or [IrCl(C2H4)2]2(7) as starting materials. The corresponding carbonyl derivativestrans‐[IrCl(CO)L2] (6, 10, 11) are obtained along similar routes. Photolysis oftrans‐[IrCl(C2H4)L2] (L =2a, 2b) leads, by intramolecular C–H activation, to the formation of the octahedral hydrido(vinyl)iridium(III) compounds [IrHCl(CHCH2)(k‐L)(k2‐L)] (16, 17), which are highly fluctional in solution. Carbonyl(hydrido)(vinyl) complexes are accessible either from16or17and CO, or fromtrans‐[IrCl(C2H4)L2] (L =2a) and the propargylic alcohol HCCCH(Ph)OH, respectively. Treatment of3or the corresponding dihydrido compound [IrH2ClL2] (4) with methyl vinyl ketone or methyl acrylate also yields hydrido(vinyl)iridium(III) complexes [IrHCl(CHCHX)L2] [X = C(=O)Me (18), C(=O)OMe (19)], in which instead of the CO function of the phosphanyl ester the carbonyl group of the vinylic moiety is coordinated to the metal. The reaction of16(L =2a) with terminal alkynes HCCR (R = Ph, CO2Me) affords the structurally related alkynyl(hydrido)iridium(III) compounds [IrHCl(CCR)(k‐L)(k2‐L)] (28, 29), while from16and internal alkynes RCCR) the iridium(I) complexestrans‐[IrCl1(RCCR)L2] (30, 31) are obtained, Stepwise treatment oftrans‐[IrCl(RCCR)L2] (6: L =2a) with NaN(SiMe3)2, (ii) H2O, and (iii) HCl leads, in the coordination sphere of the metal center, to a conversion ofiPr2PCH2CO2Me toiPr2PCH2CO2H via the isolated phosphanylenolate and phosphanyla

ISSN:0009-2940    

DOI:10.1002/cber.19971301107

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractAxial‐chiral mono‐ and biscarbene complexes of chromium containing the 1,1‐binaphthyl skeleton have been obtained in both racemic and enantiopure forms in a one‐pot reaction starting from lithiated 2,2‐dimethoxy‐1,1‐binaphthyl (1) and hexacarbonyl chromium via the Fischer route. An X‐ray structure analysis of the biscarbene complex2reveals that the biscarbene functionalization significantly increases the dihedral angle defined by the biaryl planes. The enantiopure complexes have been characterized by

ISSN:0009-2940    

DOI:10.1002/cber.19971301108

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe reactions of alkyldichlorophosphanes1(RPCl2; R =tert‐butyl:1a, R = isopropyl;1b, R = 1‐adamantyl:1c) with the germanium dichloride dioxane complex were followed by31P NMR. Depending on the organic substituents and the reaction conditions, mixtures of trichlorogermylphosphanes RP(GeCl3)24a‐c, RPHGeCl35a‐c, diphosphanes R(H)PP(H)GeCl36a‐c, R(Cl)PP(H)GeCl37a, bcyclophosphanes, and Ge‐P heterocycles such as triphosphadigermolanes (RP)3(GeCl2)28a, band tetraphosphagermolane (RP)4)GeCl210bare formed. As a further unexpected byproduct of the reaction of1awith GeCl2–dioxane, a small amount of tri‐tert‐butyl(trichlorogermyl)cyclotetraphosphane9awas isolated. From the reaction of1cwith two equivalents of GeCl2–dioxane, separation from byproducts5cand6cby crystallisation furnished colourless crystals of4c(R = 1‐adamantyl) as the first pure organylbis(trichlorogermyl)phosphane. Surprisingly, the reaction ofisoprophylphosphane with germanium tetrachloride, intended to prepare5a, led to crystalline isopropylphosphonium trichlorogermanate(II)11. The structures of molecular4cand9aand ionic11were determined by

ISSN:0009-2940    

DOI:10.1002/cber.19971301109

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractChlorophosphanes RR'PCl (1a: R,R' =1b: R =tBu, R' =iPr,1c: R =iPr, R' = Et2N,1d: R = Et2N react with the dichlorogermylene dioxane complex2furnishing trichlorogermylphosphanes RR'PGeCl34a–d. In the cases of1c/4cand1d/4dthe insertion reaction remain incomplete; similarly,4aalways contains, shortly after isolation in pure state, small amounts of1athat can be detected by NMR. A provided by the reaction of trichlorosilylphosphanetBu(Et2N)PSiCl3(5d) with GeCl4. The alkyl(dialkylamino) trichlorogermylphosphane4dexists only in an equilibrium with chlorophosphane1d, which coordinates GeCl2leading to the dichlorogermylene complex3d. A 1:1 mixture of4awith1ais formed by the novel cleavage (“chlorogermylation”) of the P–P bond of tetraisopropyldiphosphane with germanium tetrachloride. Di‐tert‐butyl(trichlorogermyl)phosphane4e(R, R' =tBu) reacts with silver bromide providing a crystalline silver complex7. A structure determination by X‐ray diffraction reveals that7is [Ag4Br4(tBu2PCl)2(tBu2PGeCl3)2]. 2C7H8. Two of the Ag atoms of the cubane‐like (AgBr)4core of7are coordinated by chlorophosphane1e, the other two by trichloroge

ISSN:0009-2940    

DOI:10.1002/cber.19971301110

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractRubidium salts withN‐(Arylazoalkenoyl)azacoronands (2a–c), were investigated using87Rb and13C solid‐state NMR spectroscopy. From the NMR results it is concluded that there is a host‐gust interaction. This suggests that the rubidium and ammonium ions, respectively, are incorporated into the cavity between the coronand and the chro

ISSN:0009-2940    

DOI:10.1002/cber.19971301111

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe reaction of niobocene trihydride [Cp2NbH3] with ClPbMe3in the presence of amine affords the plumbido dihydride complex [Cp2NbH2(PbMe3)] (1). Compound1represents the first example of a stable complex with neighbouring hydride and terminal plumbyl substituents. The structure of this compound has been established by NMR and IR spectroscopy and confirmed by an X‐ray structure analysi

ISSN:0009-2940    

DOI:10.1002/cber.19971301112

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY