Knowledge Bank

The electronic states of the metal complexes of $MCO2$ and $MCS2$ are little known. RHF, Cl and perturbation calculations were performed to establish the bond strengths, the stable geometries, and the electron distributions of these molecules. Four planar modes of coordination (which will be called ``forms'' hereafter) were studied in this work: $\eta 01$ form (end-on, coordinated by an oxygen atom), $\eta oco2$ form ($C2v$, with the carbon and two oxygen atoms approximately at the same distance from M), $\eta Co1$ form (side-on, with an oxygen and the carbon atoms at the same distance from M) $\eta c1$ form($C2v$, coordinated by the carbon atom), and the equivalent geometries for the $CS2,\eta o1,\eta oco1,\eta co2$, and $\eta C1$. The $M-CO2$ bonds are stronger than the corresponding $M-CS2$ bonds for $M=Ca,Sc,Ti$ and V, while the reverse is true for M = Cr and Cu. The stability order for geometry is $\eta o1>\eta oco1>\eta co2>\eta c1$ for $MCO2$, and $\eta SCS3>\eta CS2>\eta C1>\eta S1$ for $MCS2$. Several factors involved in the bonding between the metal atoms and the carbon dioxide or the carbon disulfide are analyzed. The ground state has the maximum spin electron configuration. Other high-spin states, which only differ from the ground states by electron permutations within the nonbonding d-subshell, are very close to the ground state. The spin populations show a transfer of one metal valence electron to the $CO2$ or $CS2$ group, which is essentially localized at the sp-hybridized AO of the carbon atom.