SYNTHESIS AND CHARACTERIZATION OF M2(EPH3)2(NME2)4 COMPOUNDS (E = C, SI, GE, SN, M = MO, W)

The reaction between M2Cl2(NMe2)4 and LiEPh3 (2 equivalents) (M = W; E = C, Si, Ge, Sn; M = Mo; E = Si, Ge, Sn) in toluene/THF at room temperature produces a precipitate of M2(EPh3)2(NMe2)4 in 35-65% isolated yield. The compounds are air-, water- and light-stable for prolonged periods in the solid state (except when E = C). All are soluble in aromatic hydrocarbon solvents and decompose on heating at 161-270-degrees-C. They were characterized by IR, UV, mass spectrometry and VT H-1 NMR. The latter revealed only the anti isomer in solution with T(c) greater-than-or-equal-to 115-degrees-C and DELTAG(dagger) greater-than-or-equal-to 74 kJ mol-1 for the amide rotation (M = W, Mo; E = Si, Ge). For W2(SnPh3)2(NMe2)4 a coalescence point of T(c) = 75-degrees-C (DELTAG(dagger) = 70 kJ mol-1) was observed and the compound slowly isomerizes to a mixture of the gauche and anti configurations.