Reaction of tungsten(VI) tetrachloride sulphide and selenide and the analogous bromides with a range of donor molecules

The compounds WX4Y (Y = S and Se, X = Cl and Br) have been allowed to react with a range of ligands containing nitrogen, phosphorus, oxygen, and sulphur donor atoms. Simple six-co-ordinate adducts WX4Y,L and 2WX4Y,L' (L = unidentate and L' = bidentate ligand) have been isolated in many cases and characterised. In these adducts the terminal WY bond is retained. Under more severe reaction conditions, longer reaction period or higher temperatures, tungsten can be reduced to the quinquevalent or quadrivalent state. Thus MeSCH2CH2SMe (mte) gives WCl3S,mte, while triphenylphosphine both reduces tungsten and extracts sulphur or selenium to give tungsten(IV) adducts of the type WX4,PPh3,P(Y)Ph3.