Group 12 Carbonates and their Binary Complexes with Nitrogen Bases and FH2 Z Molecules (Z=P, As, Sb): Synergism in Forming Ternary Complexes.

MCO3 (M=Zn, Cd, Hg) forms a spodium bond with nitrogen-containing bases (HCN, NHCH2 , NH3 ) and a pnicogen bond with FH2 Z (Z=P, As, Sb). The spodium bond is very strong with the interaction energy ranging from -31 kcal/mol to -56 kcal/mol. Both NHCH2 and NH3 have an equal electrostatic potential on the N atom, but the corresponding interaction energy is differentiated by 1.5-4 kcal/mol due to the existence of spodium and hydrogen bonds in the complex with NHCH2 as the electron donor. The spodium bond is weakest in the HCN complex, which is not consistent with the change of the binding distance. The spodium bond becomes stronger in the CdCO3 <ZnCO3 <HgCO3 sequence although the positive electrostatic potential on the Hg atom is smallest. This is because the electrostatic interaction is dominant in the spodium-bonded complexes of CdCO3 and ZnCO3 but the polarization interaction in that of HgCO3 . The pnicogen bond is much weaker than the spodium bond and the former has a larger enhancement than the latter in the FH2 Z⋅⋅⋅OCO2 M⋅⋅⋅N-base ternary complexes.