HCO(CO)4 AND HCO(CO)3 REVISITED - STRUCTURE AND ELECTRONIC STATES THROUGH ABINITIO CALCULATIONS

The structure and electronic states of HCo(CO)4 and HCo(CO)3 were investigated by means of contracted CI calculations using as reference wave function a CASSCF wave function. For HCo(CO)4 the trigonal-bipyramid structure of C3v symmetry (with the H atom axial) is found to be more stable than the one of C2v symmetry (with the H atom equatorial), by 15 kcal/mol. The 3E state of HCo(CO)4 is calculated at 24 250 cm-1, and the 1A1 → 1E excitation energy is estimated to be in the range 34 000-36 000 cm-1. The ground state of HCo(CO)3 is assigned to the closed-shell state 1A1 of the C3v structure, with the 3A2 state (corresponding also to the C3v structure) 7 kcal/mol higher and a trigonal-bipyramid structure (with the hydrogen atom and a carbonyl as axial ligands) in the closed-shell 1A′ state 10 kcal/mol higher. © 1990 American Chemical Society.