Density functional description of the early stages of the dioxygenation of[(MeC(CH2PPh2)(3))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)](+) com plexes [M = Co(III), Ir(III); triphos = MeC(CH2PPh2)(3)], which have been c onsidered to be models of ring-opening dioxygenases. The structural feature s of the starting complexes and of the intermediate complexes formed by add iton of O-2 to the coordinated cacecholato ion are well reproduced, The cal culations showed that this preliminary stage can be obtained only when the oxygen molecule attacks the molecule on the catecholato site.