Computational Investigation of the Mechanism for the Activation of CO by Oxorhenium Complexes

Abstract

In this paper a computational analysis (B3PW91) of the previously reported reaction of (O)Re(Me)(DAAm) (1; DAAm = N,N-bis(2-arylaminoethyl)methylamine, aryl = C6F5) with CO to produce (CO)Re(OAc)(DAAm) (2) is described. The data suggest that this transformation proceeds by two novel elementary steps that are of fundamental interest to the broader organometallic/inorganic community: (a) direct insertion of CO into the rhenium–methyl bond in 1 to yield the acyl intermediate (O)Re(Ac)(DAAm) (3) and (b) 1,2-migration, in the presence of CO, of the acyl fragment in 3 to the oxo ligand to yield 2. Evidence is provided for the first example of an insertion reaction where CO inserts directly into a M–R bond without prior formation of a CO adduct. In addition, it was shown that the addition of CO is necessary for the 1,2-migration of the acyl ligand. The data suggest that the addition of CO effectively weakens the Re–Cacyl bond in 3 and enables the facile migration of the acyl ligand.