摘要:

AbstractWhereas the reaction of ethylene and triethylaluminum under pressure at 100°C yields trialkylaluminum compounds having long alkyl chains, the presence of small amounts of nickel salts induces the formation of butene. The discovery of this “nickel effect” represents the starting point for the development of the Ziegler catalysts. Comparatively little was formerly known about the nature and the mode of action of the catalytically active nickel species. A basis for the elucidation of the effect was provided by studies on the reduction of nickel compounds by organoaluminum compounds, on the occurrence and existence of nickel hydrides, and on interactions between nickel(0) and Lewis acids as well as organic compounds of main group metals. The most significant result of these studies is the recognition that multicenter bonding systems involving trialkylaluminum compounds and nickel atoms are involved. These react further with complex bonded ethylene in what is probably a concerted ma

ISSN:0570-0833    

DOI:10.1002/anie.197309431

出版商:Hüthig&Wepf Verlag    

年代:1973

数据来源: WILEY

摘要:

AbstractThe progress made in the field of homogeneous catalysis during the last five to six years has led,inter alia, to the development of highly selective catalysts for asymmetric syntheses. Homogeneous asymmetric hydrogenation, using well defined transition metal catalysts, may be achieved with optical yields of 85 to 90% or more. Catalytic reactions, in which the chiral centers are generated by CC bond formation, can result in optical yields of 70 to 80%. The hydrogenation catalysts consist primarily of rhodium(I) complexes containing “Homer phosphanes”, phosphanes with chiral C atoms, or optically active amides. Catalysts which induce optical activity through the formation of CC bonds have been developed from π‐allylnickel halides, Lewis acids, and phosphanes containing chiral C atoms. The results obtained signify a breakthrough in an area of catalysis previously restricted to syntheses involvi

ISSN:0570-0833    

DOI:10.1002/anie.197309541

出版商:Hüthig&Wepf Verlag    

年代:1973

数据来源: WILEY

摘要:

AbstractThe following report describes the preparation and reactions of organocobalt compounds, especially the thermally unstable tris(π‐allyl)cobalt and cyclooctenylcobalt compounds. The stoichiometric and catalytic transformations of these highly reactive organocobalt systems give an insight into the rôle of cobalt in homogeneous catalysis involving alkenes and alky

ISSN:0570-0833    

DOI:10.1002/anie.197309641

出版商:Hüthig&Wepf Verlag    

年代:1973

数据来源: WILEY

摘要:

AbstractThis report is concerned not only with the syntheses of new ring systems and the preparation of derivatives of known rings but also with new types of catalysts based upon,e. g., nickel, iron, molybdenum, manganese, and palladium. The broad applicability of the methylene insertion reaction as a method for identifying mono‐ and di‐methyl‐substituted eight‐, ten‐, and twelve‐membered rings is also demonstrated. A further section is concerned with the possible mechanism of CC bond formation in transition metal complexes; several earlier suggestions have been revised in the light of new experimental data. In addition, experimental results are discussed which indicate that the reactivity and selectivity of the complexes formed by the nickel‐ligand catalyst and olefins or alkynes depend upon the structure

ISSN:0570-0833    

DOI:10.1002/anie.197309751

出版商:Hüthig&Wepf Verlag    

年代:1973

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197309891

出版商:Hüthig&Wepf Verlag    

年代:1973

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197309911

出版商:Hüthig&Wepf Verlag    

年代:1973

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197309931

出版商:Hüthig&Wepf Verlag    

年代:1973

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197309941

出版商:Hüthig&Wepf Verlag    

年代:1973

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197309951

出版商:Hüthig&Wepf Verlag    

年代:1973

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197309961

出版商:Hüthig&Wepf Verlag    

年代:1973

数据来源: WILEY