Hydrogen transfer to coordinated

Hydrogen Transfer to Coordinated Acyls The Molecular Structure of (C,H ),Re [(C HyZrCHs] (OCHCH )... 

The eq. (ii) involves the b-hydrogen transfer to coordinated olefin, eq. (iii) the insertion of CO to form acyl and eq. (iv) the acyl cleavage by hydrogen. This process is frequently followed by reduction of the aldehyde to an alcohol. 

The first step in this process is an oxidative addition that is followed by a hydrogen transfer to a coordinated ethene molecule to convert it to an ethyl group. The third step involves the addition of a ligand as the C2H4 molecule undergoes an insertion reaction to give a coordinated butyl group. 

In their original studies, Wilkinson and co-workers postulated a mechanism involving oxidative addition of hydrogen to rhodium(I) to give a rhodium(III) dihydride, followed by coordination of alkene. The precise nature of the hydrogen transfer to the alkene was not clear at that time, but the general outlines of the mechanism were correct. 

Under pressure of CO and H2, the cobalt catalyst precursor is transformed into cobalt carbonyl hydride, HCo(CO)4. The main steps of the reaction mechanism, first elucidated by D. S. Breslow and R. F. Heck, involve (a) /3-hydrogen transfer to the coordinated olefin, (b) the insertion of CO to form an acyl intermediate, and (c) the hydrogenolysis of the acyl, with formation of the aldehyde product ... 

The process involves initial formation of Ph M by halide replacement, followed by hydrogen transfer to allow arene -coordination . The reaction conditions complement those of the metal halide-aluminum halide-aluminum metal method and may be useful with specifically substituted arenes. 

Both unimolecular /3-hydrogen transfer to the metal and bimolecular /3-hydrogen transfer to a coordinated monomer molecule have been theoretically investigated (Figure 18). 

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