Migratory CO Insertion Reactions of Metal Alkyls

Kinetic and Mechanistic Studies of Stoichiometric Reaction Steps 3.3.2.1 Migratory CO Insertion Reactions of Metal Alkyls 

Model studies of iridium catalysed methanol carbonylation [37-39] 

As described above (Section 3.3.1.1), in situ HP IR measurements under catalytic conditions identified the anion [MeIr(CO)2l3] as the catalyst resting state in the Cativa process. The rate controlling step in the catalytic cycle was proposed to be carbonylation of [MeIr(CO)2l3] (Eq. (7)). 

A CIR cell was also used by Gonsalvi et al. to monitor carbonylation of the Ir(iii) methyl complexes, [MeIr(CO)(L-L)l2] (where L-L = dppe or dppms) [56], Under 10 bar CO, in PhCl containing 1 % methanol, a rate constant of 7.3 X 10 s was measured for the dppms complex. Under the same conditions, by contrast, the dppe complex was unreactive, reflecting the different rates of methyl migration found for the analogous Rh complexes. Both steric and electronic effects can account for these ligand effects. 

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