摘要:

A review of recent structure determination of non-metal anions containing simple ligands, mostly halogenes, is given, where the total number of ligands exceeds 6. It will be shown that these anions exist in the form of regular polyhedra, the pentagonal bipyramid and the square antiprism. A non-bonding electron pair (or two) will influence such geometries in a complex way: the general principle that such pairs are stereochemically active needs to be carefully revised in compounds of large coordination numbers.

ISSN:0260-3594    

DOI:10.1080/02603599108053474

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Carbon suboxide, C3, O2, reacts with a great variety of organometallic compounds. With organo-silicon and aluminium compounds it reacts with the C˭O moiety, giving sililation and carboalumination reactions. Insertion reactions of C˭C are performed with compounds having M-H, M-OR, M-NR2, M-PR2bonds (M ≠ Si, Al), giving mono-metal derivatives (ketenyl) or di-metal derivatives of acil groups (amides, esthers, phospides). The coordination of C˭O or C˭C to transition metal complexes, the formation of allenic compounds and the decarbonylation reactions allow the synthesis of a series of particular metal derivatives (ketenyl, ketenylidene and carbonyl complexes) which, in some cases, present a peculiar reactivity.

ISSN:0260-3594    

DOI:10.1080/02603599108053475

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In terms of the Langford—Gray mechanistic classification, simple ligand substitution in octahedral complexes in donor solvents may be described as anIprocess in all cases; it is doubtful whether the criteria forDorAmechanisms could ever be met. It is argued, however, that no meaningful, unequivocal assignments along theD/D1/Id/Ia/Alines can be made for octahedral substitution, and that attempts to make them are actually counterproductive. Instead, we should seek means of expressing the selectivity shown by various substrates towards nucleophiles, and also the lifetimes of putative intermediates, at least semi-quantitatively. Computer modelling can provide important insights into the mechanism of reaction, particularly into the key role played by the solvent in the activation process. Certain complexes of metals of the second transition series show anomalous lability; the effect requires experimental and theoretical clarification, but appears to have relativistic origins.

ISSN:0260-3594    

DOI:10.1080/02603599108053476

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor