Theoretical studies of CO interaction on Rh3 cluster

Abstract

Geometries and energy separations of 27-low-lying electronic states of Rh3CO with different structures have been investigated. Atop, bridged, and threefold CO orientations with Rh3 were considered. Complete active space multiconfiguration self-consistent field method (CASMCSCF) followed by large scale multireference singles and doubles configuration interaction (MRSDCI) computations that included up to 2.1 million configurations were used. Three nearly degenerate electronic states were found for the threefold structure around the minimum energy region. At the highest level of theory, the A22 state prevailed to be the ground state. The assignment of minimum energy states for the atop and bridged structures are unambiguous. The B42 and B41 electronic states were found to be the most stable states for these two respective geometries. The nature of the metal–CO bond formation in different states is discussed, and the difference density maps of Rh3CO with respect to Rh3 and COs are presented. The dissociation energies and CO vibrational frequencies have been computed and the results are compared with the available experimental data.