SYNTHESIS AND CHARACTERIZATION OF TUNGSTEN SILOXIDES INCLUDING THE CRYSTAL-STRUCTURE OF [WO(O(PH2SIO)(3))(2)(THF)]

Reactions of WOCl4 with NaOSiPh3 and Na2O2SiPh2 gave respectively [WO( Cl)(OSiPh3)(3)] and [{WO2[(OSiPh2)(2)O]}(2)]. Under similar conditions NaOSiPh3 reacted with [WO2Cl2(OSC4H8)(2)] to yield [WO2(OSiPh3)(2)(OS C4H8)(2)]. The novel spirocyclic tungstasiloxane [WO{O(Ph2SiO)(3)}(2)( thf)] was prepared from the reaction between equimolar quantities of ( Ph2SiO)(3) and WOCl4 in tetrahydrofuran. A crystal structure determina tion on this product revealed a distorted octahedral geometry about th e central tungsten atom with the axially co-ordinated ether ligand tra ns to the oxo group, and puckered eight-membered siloxane rings orient ed on opposite sides of the equatorial plane defined by the four co-or dinated siloxide O atoms. The W-O (Si) separations ranged from 1.851(7 ) to 1.896(8) Angstrom and the W=O bond length was 1.675(13) Angstrom. In dichloromethane WCl6 reacted with (Ph2SiO)(3) to afford good yield s of WOCl4, whereas in tetrahydrofuran the same reactants caused solve nt polymerisation.