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.