Reversible metal-to-metal methyl transfer in .eta.5-cyclopentadienyl(triphenylphosphine)dimethylcobalt(III)

Labeling techniques have been used to demonstrate that {eta}{sup 5} cyclopentadienyl(triphenylphosphine)dimethylcobalt(III) (1) undergoes intermolecular cobalt-to-cobalt methyl group exchange. The reaction follows second order kinetics; rate constants for methyl exchange between complexes 1 and its methylcyclopentadienyl analog 4 show decreasing magnitude with increasing bulk of cyclopentadienyl substituents. Studies of the reaction with excess triphenylphosphine and complexes labeled with the non-dissociating trimethylphosphine ligand indicate the reaction requires dissociation of phosphine from one of the two partners in the exchange before scrambling can take place. Further studies with other complexes (e.g., Cp{sub 2}Zr(CH{sub 3}){sub 2}) suggest that alkyl exchange between two transition metal centers may be a more general reaction than has heretofore been suspected