Model Studies of Migratory Insertion in the Rh System

Since [RhMe(CO)2l3] could be quantified, it was also possible to estimate the rate constant for the formation of [Rh(C(0)Me)(C0)l3] from [RhMe(CO)2l3] . Rh(C(0) Me)(CO)l3] had also been shown to eliminate Mel to regenerate [Rh(CO)2l2] and the reactions are therefore reversible. 

The effect of solvent polarity on the rate of the individual steps was also deduced from a comparison of the kinetics determined by IR. It was concluded that, comparing MeOH/Mel (80 20 v/v) with CH2Q2/MCI (80 20 v/v), the overall increase in rate of reaction of [Rh(CO)2l2] with Mel to give [Rh(C(0)Me)( CO)I] included contributions due to enhancement of the forward rates of both oxidative addition (ca. 50%) and migratory insertion (ca. 100%). 

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