Coupling between the nickel—carbon and carbon—oxygen stretch motion in NiCO

Linear-combination-of-Gaussian-type-orbital Xα calculations on NiCO are described. The electronic structure and equilibrium bond distances R_Ni-CO=3.11a₀ and R_NiC-O=2.18a₀ are consistent with recent configuration-interaction calculations employing core pseudopotentials. The computed Ni---CO and NiC---O harmonic vibrational frequencies are 656 and 1933 cm^-1. The CO stretch vibration is within 100 cm^-1 of experiment and the ratio of intensities for those two modes, 640, is consistent with the fact that the Ni---C stretch has not been seen in matrix isolation experiments. The relevance of NiCO as a model for CO adsorbed on solid nickel is discussed and found to be marginal.