Synthesis, properties and structural features of molybdenum(v) oxide trichloride complexes with neutral chalcogenoether ligands.

Complexes of oxotrichloromolybdenum(v) with neutral group 16 donor ligands, [MoOCl(L-L)] (L-L = RS(CH)SR, R = Pr, Ph; MeS(CH)SMe; MeSe(CH)SeMe; MeSe(CH)SeMe), [{MoOCl(EMe)}(μ-Cl)] (E = S, Se, Te), [(MoOCl){o-CH(EMe)}] (E = Se or Te) and [(MoOCl){MeTe(CH)TeMe}], have been obtained by reaction of the ligands with [MoOCl(thf)] or MoOCl in either CHCl or toluene, and characterised by microanalysis, IR and UV-visible spectroscopy and magnetic measurements. The telluroethers are the first examples containing Mo in a positive oxidation state. X-ray crystal structures are reported for the six-coordinate fac-[MoOCl{MeS(CH)SMe}], mer-[MoOCl{PrS(CH)SPr}] and mer-[MoOCl{MeSe(CH)SeMe}], as well as the six-coordinate chloride-bridged dimers, [{MoOCl(SMe)}(μ-Cl)] and [{MoOCl(SeMe)}(μ-Cl)]. The structure of the mixed-valence decomposition product, [MoCl{o-CH(TeMe)}(μ-O)MoOCl], was also determined. In toluene solution MoOCl is reduced by MeS(CH)SMe to produce the Mo(v) complex, [MoOCl{ MeS(CH)SMe}]. Crystal structures of the previously unknown diphosphine analogue, [MoOCl{MeP(CH)PMe}], and the mixed-valence derivative [MoCl{MeP(CH)PMe}(μ-O)MoOCl] are also reported for comparison and help to clarify earlier contradictory literature reports. In contrast to the dimeric EMe complexes, [{MoOCl(EMe)}(μ-Cl)], PMe forms the monomeric complex, fac-[MoOCl(PMe)].