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

Linear-combination-of-Gaussian-type-orbital $X\alpha$ calculations on NiCO are described. The electronic structure and equilibrium bond distances $R_{\mathrm{Ni}-\mathrm{CO}}=3.11\mathrm{}{a}_0$ and $R_{\mathrm{NiC}-\mathrm{O}}=2.18\mathrm{}{a}_0$ are consistent with recent configuration-interaction calculations employing core pseudopotentials. The computed Ni—CO and NiC—O harmonic vibrational frequencies are 656 and 1933 ${\mathrm{cm}}^{-1\mathrm{}}$. The CO stretch vibration is within 100 ${\mathrm{cm}}^{-1\mathrm{}}$ 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.