The recognition of a new pathway for the reaction of molecular oxygen with a Pd(II)-hydride to produce a Pd(II)-hydroperoxide

Significant recent developments in homogeneous palladium catalysis for selective aerobic oxidation have emphasized the importance of developing a thorough comprehension of reactions of palladium complexes with O-2. Density functional theory (DFT) calculations, employing the B3LYP exchange-correlation functional, have been performed to probe the mechanism for the insertion reaction of molecular oxygen into the palladium(II) hydride bond of the trans-[PdH(O2Ac)(IMes)(2)] complex to form the corresponding Pd(II)-hydroperoxide. A crossing between triplet and singlet surfaces occurs before the formation of a stable singlet intermediate from which the reaction straightforwardly proceeds to yield the singlet hydroperoxo complex. Results appear to be different with respect to previous analogous theoretical investigations providing a new minimum energy pathway. (C) 2008 Elsevier B.V. All rights reserved.