Enhancing effect of metal coordination interaction on pnicogen bonding.

The ternary complexes ML∙∙∙PyZX2∙∙∙NH3 (ML = CuCl, CuCN, AgCN, and AuCN; Z = P, As, and Sb; X = H and F) have been investigated with quantum chemical calculations. The results showed that the existence of coordination interaction has a prominent enhancing effect on the strength of pnicogen bonding. Even in ML∙∙∙PySbH2∙∙∙NH3, ML∙∙∙PyAsF2∙∙∙NH3, and ML∙∙∙PySbF2∙∙∙NH3, the pnicogen bond varies from a purely closed-shell interaction to a partially covalent interaction. The coordination interaction results in the enlargement of the σ-hole on the pnicogen atom and thus the enhancement of pnicogen bonding. In addition, the contribution of orbital interaction is also important.