Acidification of [WS 4 ] 2– . Synthesis and structures of di-µ-sulfido-bis[(2,2′-bipyridine)chlorooxotungsten( V )] and di-µ-sulfido-bis[(2,2′-bipyridine)bromooxotungsten( V )]

Acidification of [WS4]2– by HCl or HBr in MeCN in the presence of 2,2′-bipyridine (bipy) led to the neutral dinuclear complexes [W2S2O2X2(bipy)2](X = Cl 1 or Br 2) which have been isolated as crystals. The structures of 1 and 2 were solved by X-ray diffraction methods, and were found to be isomorphous. Each tungsten(V) is bonded to a bipy ligand throuph the two nitrogen atoms, one in an axial, and the other in an equatorial position. The remaining axiai position of the octahedron is occupied by a terminal oxygen. The co-ordination is completed by a terminal halide and a bridging sulfur. A metal–metal bond is postulated between the two WV atoms, in accord with the diamagnetism of the crystals. The formation of compounds 1 and 2 has been analysed in comparison to the formation of [W4S12]2– under the same conditions of acidity but in the absence of 2,2′-bipyridine.