STRUCTURES AND FOND ENERGIES OF THE TRANSITION-METAL CARBONYLS M(CO)(5) (M=FE, RU, OS) AND M(CO)(4) (M=NI, PD, PT)

The equilibrium geometries of the transition-metal carbonyls M(CO)(n) (M = Fe, Ru, Os; n = 4, 5) and M(CO), (M = Ni, Pd, Pt; n = 3, 4) are c alculated at the MP2 level using effective core potentials for the met als and 6-31G(d) basis sets for C and O. The first ligand dissociation energies of the saturated metal carbonyls are theoretically predicted using the coupled duster theory (CCSD(T)) approach. The calculated di ssociation energies Delta H-298 (Fe-(CO)(5), 46.5 kcal/mol; Ru(CO)5, 3 0.9 kcal/mol; Os(CO)(5), 42.4 kcal/mol; Ni(CO)(4), 24.4 kcal/ mol; Pd( CO)(4), 9.6 kcal/mol; Pt(CO)(4), 13.0 kcal/mol) indicate that the seco nd-row transition elements have the weakest carbonyl bond.