KINETIC AND THERMODYNAMIC CONTROL OF THE METHYL MIGRATION (CO INSERTION) REACTION BY STRONG LEWIS-ACIDS

The activation of metal-coordinated carbon monoxide and in particular the alkyl migration reaction is a subject of considerable fundamental and technological importance.1-3 As shown in eq 1, this reaction involves the migration of the alkyl group onto one of the coordinated carbonyls accompanied by the addition of a ligand to an alkyl metal carbonyl forming a metal-acyl complex. For the special case of an anionic metal carbonyl, alkyl migration is accelerated by small alkali metal ions, which ion pair with the metal carbonyl.4 As with reaction 1, an incoming ligand is still required for this cation assistd reaction. In the course of studying the potentially more general molecular Lewis acid assistance of alkyl migration (a reaction which would not be confined to anionic alkyl metal carbonyls), we were surprised to find a very fast methyl migration reaction in the absence ofadded CO. The mechanism of formation, structure, and reactivity of these novel methyl migration products are discussed below. © 1979, American Chemical Society. All rights reserved.