The reactions of tetrahydridotetrakis(methyldiphenylphosphine)-molybdenum(IV) and -tungsten(IV) with acids
Abstract
Neutral and cationic hydrido-complexes of molybdenum and tungsten have been prepared by interaction of the compounds MH4(PMePh2)4(M = Mo and W) with acids HX (X = CF3CO2, p-MeC6H4SO3, BF4, and PF6). The reactions of MoH4(PMePh2)4 are accompanied by hydrogen evolution and yield different MoIV products that depend on the nature of the anion, namely neutral species MoH2X2(PMePh2)3(X = CF3CO2 and p-MeC6H4SO3) and cationic species [MoH3(PMePh2)3]X (X = BF4 and PF6). By contrast WH4(PMePh2)4 is readily protonated to give the cationic pentahydrido-species [WH5(PMePh2)4]+. The corresponding trifluoroacetate isolated as [WH5(PMePh2)4][H(O2CCF3)2]·toluene loses hydrogen on melting to yield the neutral compound WH2(CF3CO2)2(PMePh2)3.
With hydrochloric acid MoH4(PMePh2)4 gives a green compound Mo2Cl4(PMePh2)4 which readily transforms into a blue isomer, while WH4(PMePh2)4, gives again the WH5(PMePh2)4+ ion. The compounds are characterised by i.r. and 1H and 31P n.m.r.spectroscopy.