The preparation and characterization of M2(OEPh3)2(NMe2)4,where M = Mo and W and E = C and Si. The x-ray crystal structures of gauche-W2(OCPh3)2(NMe2)4, anti-Mo2(OCPh3)2(NMe2)4 and anti-W2(OSiPh3)2(NMe2)4

Abstract

Reaction of M2(NMe2)6 (M = Mo, W) with triphenylmethanol in hexane/ether produces M2(OCPh3)2(NMe2)4 (I) as yellow crystals in high yield (92–97%). M2 (OCPh3)2(NMe2)4 are air-sensitive, soluble in aromatic solvents and decompose around 160°C. The 1H NMR of I is temperature dependent and shows a mixture of anti and gauche rotamers. The X-ray crystal structures of I reveal exclusively the gauche isomer for tungsten and the anti isomer for molybdenum. The reactions between M2(NMe2)6 and triphenylsilanol (2 equiv.) yield M2(OSiPh3)2(NMe2)4 compounds (M = Mo, W) (II) as orange crystals. In the presence of ρ6 equiv. of Ph3SiOH the M2(NMe2)6 compounds react further to give yellow crystalline compounds, M2(OSiPh3)4(NMe2)2. In.compound II, where M = W, the W2O2N4 skeleton adopted the anti conformation with WW = 2.2954(6) Å, W O = 1.925(4) Å, WN = 1.935(8) Å, WWO = 108.1(1)°, WWN = 102(1)°. The addition of Ph3SiOH (6 equiv.) to W2(OBut)6 yielded the related compound W2 (OBut)2(OSiPh3)4.