Structure and Bonding in First-Row Transition Metal Dicarbide Cations MC2

A theoretical study of the first-row transition metal dicarbide cations MC2 + (M = Sc−Zn) has been carried out. Predictions for different molecular properties that could help in their eventual experimental detection have been made. Most MC2 + compounds prefer a C 2 v symmetric arrangement over the linear geometry. In particular, the C 2 v isomer is specially favored for early transition metals. Only for CuC2 + is the linear isomer predicted to be the global minimum, although by only 1 kcal/mol. In all cases the isomerization barrier between cyclic and linear species seems to be very small (below 2 kcal/mol). The topological analysis of the electronic density shows that most C 2 v isomers are T-shaped structures. In general, MC2 + compounds for early transition metals have larger dissociation energies than those formed by late transition metals. In most cases the dissociation energies for MC2 + compounds are much smaller than those obtained for their neutral analogues. An analysis of the bonding in MC2 + compounds in terms of the interactions between the valence orbitals of the fragments helps to interpret their main features.