Intermolecular π-hole/n→π* interactions with carbon monoxide ligands in crystal structures.

A thorough analysis of the Cambridge Structure Database reveals that intermolecular π-hole/n→π* interactions with carbon monoxide ligands are abundant in the solid state and somewhat directional, particularly with fac-like M(CO)3 fragments (P < 4.0). High level DFT calculations suggest interacting energies up to about -10 kcal mol-1 for adducts of charge neutral complexes.