Migratory insertions into alkoxides

Leaving aside the autoxidations of d°-alkyls, which only formally yield O2 insertion products, there are a very few examples of reactions where migratory insertion of a coordinated O2 into a metal alkyl bond seems indicated. Thus, heating of Cp 2Ta( -02)Me (Sect. 2.1) in solution in the absence of any base results in its transformation into Cp 2Ta(0)0Me [1]. Lewis acids were noted to catalyze the reaction. While there is no direct evidence for the formation of an alkylperoxo intermediate, the final product could easily be rationaUzed as resulting from an a-alkoxide eUmination (Scheme 10). 

Unsaturated compounds such as CO can be formally inserted into a metal-heteroatom bond such as hydroxide, alkoxide, amide, and sulhde. However, it presents a difficult problem to determine whether the overall insertion process proceeds through a migratory insertion process or by an alternative process. For example, the anionic ligand such as OH and alkoxides may dissociate first to provide a vacant coordinahon site for the CO ligand that is subsequently attacked by the anion to give the same product as that obtained by the migratory insertion of the anionic ligand on the coordinated CO. 

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