The CO–CO interactions in transition-metal hexacarbonyls studied by Penning ionization electron spectroscopy: Cr(CO)6, Mo(CO)6, and W(CO)6

Abstract

Penning ionization electron spectra resulting from thermal collisions of He*(2 3S) metastable atoms with gaseous Cr(CO)6, Mo(CO)6, and W(CO)6 were measured to probe the CO–CO interactions. The energy splitting of the CO 5σ-derived levels [I.P.(8a1g)−I.P.(8t1u)] was determined for the first time. Further, the spectra show that the through-space interaction among the CO 5σ orbitals not only stabilizes the orbital energy of the CO 5σ-derived 8a1g molecular orbital, but also gives rise to a diffuse electron distribution. The CO–CO interactions in the transition-metal (TM) carbonyls were compared to those in the CO overlayer formed on TM surfaces.