An effective core potential study of the mono- and tetracarbonyls of Ni, Pd, and Pt

Effective core potentials (ECP’s) are used to determine SCF equilibrium geometries and properties of the mono- and tetracarbonyls of nickel, palladium, and platinum. For Pd and Pt, potentials including relativistic effects are employed. Electron correlation effects on metal–carbon and carbon–oxygen bond lengths are evaluated by second-order Møller–Plesset perturbation theory (MP2). Inclusion of correlation enhances π backbonding. For linear MCO, the 1∑+ state lies below the 3Δ state. Agreement with all-electron calculations and experiment is satisfactory. The predicted relative stability based on metal–carbonyl bond energies of both MCO and M(CO)4 is in the order Ni>Pt>Pd, as observed experimentally.