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

In this paper a computational analysis (B3PW91) of the previously reported reaction of (O)­Re­(Me)­(DAAm) (<b>1</b>; DAAm = <i>N</i>,<i>N</i>-bis­(2-arylaminoethyl)­methylamine, aryl = C₆F₅) with CO to produce (CO)­Re­(OAc)­(DAAm) (<b>2</b>) 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 <b>1</b> to yield the acyl intermediate (O)­Re­(Ac)­(DAAm) (<b>3</b>) and (b) 1,2-migration, in the presence of CO, of the acyl fragment in <b>3</b> to the oxo ligand to yield <b>2</b>. 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–C_acyl bond in <b>3</b> and enables the facile migration of the acyl ligand