Calculation of accurate binding energies for the transition-metal carbonyls Ni(CO) 4 , Fe(CO) 5 and Cr(CO) 6

Abstract

Using new atomic natural orbital basis sets constructed to treat correlation of all M-shell electrons for the first transition row, we have calculated the energies of the reaction M(CO) n →M+nCO for M=Ni,Fe,Cr and n=4,5,6, respectively. Both coupled-cluster and multiconfigurational reference perturbation theory are used as correlation treatments, and although they give qualitatively similar results once basis set superposition error is accounted for, multireference perturbation theory gives binding energies that are larger than both coupled-cluster theory and experiment. The agreement between our best calculated results and experiment is excellent for Ni(CO)4 and Fe(CO)5, but very poor for Cr(CO)6. The experimental result for the latter is old and we suggest that revisiting this system experimentally would be valuable.