CRYSTALLOGRAPHIC AND QUANTUM-CHEMICAL ANALYSIS OF DMSO COORDINATION TO PLATINUM

Abstract

Dissolving platinum complexes in DMSO for a study of biological activity can result in ligand displacement and changes in complex structures [1]. Quantum chemical calculations indicate that the coordination of DMSO via the oxygen atom is kinetically favoured over coordination to platinum via sulfur. This is followed by ligand interconversion, which results in the S-coordination of the DMSO molecule in platinum complexes (Figure). The resulting (binding) isomer is thermodynamically more stable. A search of the Cambridge structural database identified 561 platinum complexes with an O-bound DMSO ligand. However, only 7 platinum complexes had DMSO molecule ligated through the sulfur atom. The presence of chelating or bridging ligands in the cis position with respect to the O-bound DMSO molecule can prevent the DMSO from undergoing ligand interconversion. In such cases, the DMSO molecule remains coordinated with platinum via its oxygen atom.