Density Functional Description of the Early Stages in the Dioxygenation of [(triphos)M(Catecholate)]+ Complexes [M = Co(III), Ir(III)]. Toward a rationalization of the catalytic mechanism of ring opening dioxygenases

Density Functional Theory (DFT) has been applied to characterize the early stages of the reaction of dioxygenation of [(triphos)M(catecholate)]+ complexes [M = Co(III), Ir(III); triphos = MeC(CH2PPh2)3], which have been considered to be models of ring-opening dioxygenases. The structural features of the starting complexes and of the intermediate complexes formed by addition of O2 to the coordinated catecholato ion are well reproduced. The calculations showed that this preliminary stage can be obtained only when the oxygen molecule attacks the molecule on the catecholato site