The amount of charge transferred from the anion to CO2strongly depends on the nature of the atom bonding to the carbon atom. As a general trend, the amount of charge transfer occurs in the following order: P > S ~ N > O, reflecting the reverse of the atomic electronegativity. Within a given group, the trends for charge transfer is the same as that of the relative stability of the adduct, with a larger transferred charge leading to more stable adducts. The same trend is observed for the geometrical parameters. Although the dA_CO2 distance is strongly influenced by the atomic radius, within a given group (P, S, N or O), this distance and the OCO angle are smaller for the more strongly bonded anions, although in the last case the effects are indeed small.