Tungsten oxo salicylate complexes from tungsten hexachloride reactions systems

Tungsten hexachloride is a potent halogen-transfer agent, capable of reacti ng directly with salicylic acid to generate a tungsten oxo fragment and sal icoyl chloride. As a result, oxo complexes dominate the chemistry of tungst en(VI) salicylates. Both mono- and disalicylate substituted tungsten oxo co mplexes are accessible. The Bronsted free acid W(=O)CI(Hsal)(sal) complex i s a sparingly soluble, presumably polymeric material that can be dissolved in THE The THF adduct has been characterized by NMR spectroscopy, although an X-ray crystallographic study indicates that the product cocrystallizes w ith a structurally analogous d(1) WCl2(Hsal(.)THF)(sal) byproduct. The rema ining chloride ligand in W(=O)CI(Hsal)(sal) is replaced by a bridging oxo u nit when the reaction contains a significant excess of salicylic acid. The product "linear" oxo bridged ditungsten complex, [W(=O)(Hsal)(sal)](2)O, fo rms intramolecular hydrogen bonds, accounting for its high solubility in no ncoordinating solvents. An X-ray study shows that the intramolecular Hsal(. )sal hydrogen bonding in this complex accommodates a more linear W-O-W arra ngement than does a previously observed class of isostructural diolate deri vatives. Tungsten oxo tetrachloride, formed in the initial reaction between salicylic acid and WCl6, also reacts with the salicoyl chloride byproduct to generate tungsten salicoylate (OAr-2-COCl) complexes,