Experimental and computational evidence for a stabilising C–Cl(lone-pair)⋯π(chelate-ring) interaction

Abstract

In addition to a variety of conventional non-covalent intermolecular interactions such as C–H⋯π (arene), C–H⋯Cl and π(arene)⋯π(chelate-ring) contacts, the molecular packing in the crystal of an organotin dithiocarbamate compound, [SnCl(4-ClC₆H₄)₂{S₂CN(i-Pr)₂}], exhibits evidence for a C–Cl⋯π(chelate-ring) interaction. These interactions occur via a side-on approach of the chloride atom to the chelate-ring and therefore are characterised as C–Cl(lone-pair)⋯π(chelate-ring) interactions, are shown to be attractive by NCI plots and QTAIM analysis, and are apparent in the calculated Hirshfeld surfaces. Theory suggests the energy of association provided by the C–Cl⋯π(chelate-ring) interactions to be about 3–4 kcal mol⁻¹, a value greater than for analogous C–Cl⋯π(arene) and C–H⋯π(arene) interactions. A survey of the literature for related structures suggests that these interactions are not common. The newly described C–Cl(lone-pair)⋯π(chelate-ring) interactions add to the variety of intermolecular interactions able to be formed by chelate-rings in the supramolecular chemistry of metal complexes.