A theoretical study on CO2 insertion into an M(bond)H bond (M = Rh and Cu)

Abstract

Insertion of CO{sub 2} into the transition metal-hybride bond of [Rh{sup III}H{sub 2}(PH{sub 3}){sub 3}]{sup +}, Cu{sup 1}H(PH{sub 3}){sub 2}, and Rh{sup I}H(PH{sub 3}){sub 3} was theoretically investigated with an ab initio MO/MP4, SD-CI, and CCD methods. The geometries of reactants, transition states (TS), and products were optimized at the Hartree-Fock level, and then MP4, SD-CI and CCS calculations were performed on those optimized structures. The TS of the CO{sub 2} insertion into the Cu{sup I}-H bond is the most reantantlike, while the TS of the CO{sub 2} insertions into the Rh{sup III}-H bond is the most productlike. The activation energy (E{sub a}) and the reaction energy ({Delta}E) were calculated to be 6.5 and -33.5 kcal/mol for the CO{sub 2} insertion into the Cu{sup I}-H bond, 21.2 and -7.0 kcal/mol for the CO{sub 2} insertion into the RH{sup I}-H bond, and 51.3 and -1.1 kcal/mol for the Rh{sup III}-H bond at the SD-CI level, where negative {Delta}E represents exothermicity. These results are discussed in terms of the M-H bond energy and the trans-influence of the hydride ligand. 23 refs., 3 figs., 7 tabs.