Homoleptic complexes chromium

Chromium alkyls [(>j -(3-t-Bu-5-Mepz)3B)CrR] (R = Et, CH2SiMc3, Ph) follow from the corresponding homoleptic complexes and alkyllithium compounds (97CEJ1668). 

Homoleptic diiron carbonyls, reactions, 6, 221 Homoleptic dimethylaminomethyl chromium(II) complex, preparation, 5, 294... 

Homoleptic carbonyl ligands, in palladium complexes, 8, 197 Homoleptic chromium alkyl compounds, preparation,... 

The nature of the complexes, synthesized from metal vapor and t-BuC=P, is highly dependent upon the nature of the metal. Thus, with iron, chromium, or vanadium atoms, pentaphosphametallocenes are obtained.51 In contrast, the phosphaalkyne and molybdenum or tungsten atoms afford homoleptic tris[i74-l,3-diphosphete] metal(O) complexes [M(tj4-P2C2- -Bu2)3] (M = Mo, W).51... 

UV irradiation of the homoleptic alkyl complexes of chromium was found to give homolysis of the Cr—alkyl bonds and the generation of free radicals 17, 45, 46). When Cr(nor)4 was irradiated with near-UV light in CCU/hexane mixtures, clean changes in the UV-visible absorption spectrum resulted and norbornane, 1-chloronorbornane, and hexachloroeth-ane were produced [Eq. (56)] (45). An orange, chromium-containing solid... 

Although additives to induce radical chemistry have allowed ligand substitutions of 18-electron complexes to be conducted under mild conditions, photochemical reactions provide a common and practical alternative. Photochemically induced dissociation of carbonyl ligands is most common, but photochemical dissociations of other dative ligands are known. Several examples are shown in Equations 5.36-5.40. These examples illustrate the dissociation of CO from homoleptic carbonyl compounds of iron - and chromium, the dissociation of CO from piano-stool carbonyl compounds, " ttie dissociation of N, and the dissociation of a carbodiimide to generate an intermediate that coordinates and cleaves the C-H bonds of alkanes. In some cases, like the formation of the two THE complexes, the products of the photochemical process are not isolated instead, they are treated in situ with a ligand, such as a phosphine, to form monosubstitution products selectively. 

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