Alkene, Alkyne, and Carbene Insertion

A LCAO-MO-SCF calculation of equation (45) suggests that the reaction is best described as olefin insertion and not hydride migration. Good TT-donor ligands are predicted to promote the reaction. 

Ethylene insertion into the Rh-H bond in traw5-[HRh(C2H4)(P(/-Pr3)2)] (26) has been studied using a magnetization transfer technique. In toluene-d the insertion rate is independent of added phosphine or ethylene, and therefore is truly intramolecular. The mechanism consists of very rapid trans cis equilibration of (26), followed by reversible hydride migration in the cis form. The migration step has the following activation parameters AH = 13.0 kcal moP and A5 = -2 cal moP.  

The first example of methyl migration to a coordinated arene was recently reported, equation (33)/ The rate of methylene insertion into the Pt-Pt bond of [Pt2XY(dppm)2] + (X, Y = CP, Br , T, CO, py, NH3 n = 0,1,2) to give the molecular A-frame product (27) shown in equation (34) is first order in both reactants in dichloromethane/ It is proposed that in the rate-limiting step a pair of electrons are transferred from the metal-metal bond to the methylene group of diazomethane. 

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