Oxohalo complexes of W (V) and W (IV). The synthesis and crystal structures of [WOCl (dppe)2] [BPh4], [PHMe2Ph] [WOBr4 (OPMe2Ph)] and [Li (OPMe2Ph)(THF)]2 [WOBr4 (OPMe2Ph)]2

The first title compound, 1, where dppe = 1,2 bis(diphenyl-phosphino)ethane, was prepared by reacting WCl4 with NaHS in the presence of dppe in a THF and methanol mixture. The second, 2, and the third, 3, were prepared by reacting WBr5 with LiBH4 in the presence of PMe2Ph ligand in a benzene and THF mixture under different reaction conditions. All of these complexes were characterized by single crystal x-ray diffraction studies. In each case, the coordination of the W atom is distorted octahedral. In compound 1, the Cl atom is trans to the O atom and the phosphine ligands form five membered chelate rings. In both the compounds 2 and 3, oxygen atoms are trans to each other and four bromine atoms are coplanar. In compound 3 tungsten atoms are bridged by oxygen and lithium atoms