A theoretical study of the photochemical reductive elimination and thermal oxidative addition of molecular hydrogen from and to the Ir-complex

Abstract

The electronic mechanisms of the cyclic processes of photochemical reductive elimination of H2 from [IrClH2(PH3)3] and thermal oxidative addition of H2 to [IrCl(PH3)3] are investigated theoretically. The geometries of the ground and excited states are optimized using the Hartree-Fock and single excitation configuration interaction methods, respectively, and higher level calculations for the ground and excited states are carried out by the symmetry adapted cluster (SAC)/SAC–configuration interaction method. The present calculation shows that the reductive elimination of H2 from [IrClH2(PH3)3] dose not occur thermally but photochemically through diabatic conversion from the lowest A′ excited state to the ground state (A′), while the oxidative addition of H2 to [IrCl(PH3)3] easily proceeds thermally. The lowest 1A′ excited state involves the nature of the Ir-H2 antibonding.