Polar solvents migratory insertion reactions

The rates of migratory insertion reactions are often strongly affected by the solvent. Insertions of CO conducted in polar solvents are usually faster than those conducted in non-polar solvents. For example, the rate of insertion of CO into the M-C bond of RMn(CO)j induced by addition of cyclohexylamine is 10 times faster in DMF flian it is in mesitylene. ... 

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%). 

Unconjugated olefins and acetylenes are rapidly hydrogenated in a ds manner in the presence of V fiUdnson s catalyst. These reactions typically occur at ambient hydrogen pressure and temperature in benzene when the reaction is conducted with a polar co-solvent, such as ethanol. These polar co-solvents might facilitate migratory insertion, which is the turnover-limiting step of the catalytic cycle presented later in this chapter. 

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