Sulfur insertion into group 12 metal dithiolate complexes: metal-dependent equilibria

Abstract

Dianionic bis(carboxamide)pyridine-supported metal(II) dithiolate complexes of Cd²⁺ and Hg²⁺ showed isostructural [N₃S₂] coordination to a previously reported zinc variant, but changes in ionic radius resulted in distortion of the coordination geometries. While addition of elemental sulfur to the zinc dithiolate complex selectively inserts an “S₃” unit to form a zinc tetrasulfanide complex, addition of S₈ to the Cd²⁺ or Hg²⁺ congeners formed multiple products corresponding to sulfur insertion at both thiolate moieties, with different equilibrium constants of insertion. These reactions were correlated to comparisons of metal thiolate nucleophilicity and electrochemical oxidation potentials of the dithiolate complexes. These results point to additional contributions from ring strain and other structural/steric effects in controlling the thermodynamics of sulfur insertion.