Knowledge Bank

The interaction between Ar matrix isolated $NiF2$ and CO has been studied by an ab initio molecular orbital method. First the electronic structures of $NiF2$, CO and $CO+$ were investigated using a Gaussian lobe basis set. The $NiF2$ bond angle was found to be $162\circ$, in good agreement with the experimental determination, and the NiF bond was found to have a slightly covalent character. The electronic structure of $NiF2CO$ was then determined for different NiC distances. The energy curve is rather flat, suggesting a weak interaction. The modification of the CO bond from free CO to $NiF2CO$ was then investigated. It is shown that the nearly dipositive nickel atom induces a charge polarization leading to a strengthening of the bond. This is consistent with the experimental observation of a $70 cm-1$ shift of the CO frequency towards higher frequency. Density contours are discussed.