Crystal and molecular structures of some tri-aryltin isothiocyanates (Ar 3SnNCS; Ar = C 6H 5, p-CH 3C 6H 4, o-CH 3C 6H 4, o-CH 3OC 6H 4) and of the adduct hexamethylphosphoamide ( N-thiocyanato) tris ( o-tolyl) tin

Abstract

Full crystal structures are reported for several tri-aryltin isothiocyanates. Ar 3SnNCS [Ar  Ph (A), p-Tol ( B), o-Tol (C), o-CH 3OC 6H 4 ( D)], as well for the adduct ( o-Tol) 3SnNCS·HMPA (E) (HMPA = hexamethylphosphoramide). Compound B like A has bridging thiocyanates with five-coordinate tin but C and D are the first accurately characterised monomeric Ar 3SnNCS, with four-coordinate tin. The adduct has unambiguously five-coordinate tin even with the ortho-methyls present. The small but significant changes in thiocynate bond lenghts correlate with changes in the geometry at tin, and these changes confirm that ν(CN) values do indeed accurately monitor trends in modes of thiocynate bonding when involving coordination to the same type of Lewis acid environment.