Xanthate sulfur as a hydrogen bond acceptor: the free xanthate anion and ligand sulfur in nickel tris ethylxanthate

Xanthates, like thiolates, form a variety of complexes with metals in which coordinating sulfur can serve as a hydrogen bond acceptor. Nickel tris xanthate complexes [Ni(xan)3]−, (xan = o-ethylxanthate, N-(carbamoylmethyl)ethylxanthate) have been synthesized and compared by a combination of X-ray crystallographic and spectroscopic measurements. Recent results from our studies of N–H⋯S hydrogen bonding interactions in metal–xanthate complexes shows N–S distances to be longer than those in related thiolate complexes, indicative of weaker hydrogen bonds for the xanthates. The complex (Et4N)[N-(carbamoylmethyl)ethylxanthate)] adopts an extended conformation in both the solid state and solution and lacks either intraligand or intermolecular N–H⋯S hydrogen bonds. The complex (CTA)[Ni(exa)3] exhibits N–H⋯S hydrogen bonds between the amide group of the counterion and the ligand sulfur. The amide–sulfur N–H⋯S distance is 3.567 Å.