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

Abstract

Complexes of oxotrichloromolybdenum(V) with neutral group 16 donor ligands, [MoOCl₃(L–L)] (L–L = RS(CH₂)₂SR, R = ⁱPr, Ph; MeS(CH₂)₃SMe; MeSe(CH₂)₂SeMe; MeSe(CH₂)₃SeMe), [{MoOCl₂(EMe₂)}₂(μ-Cl)₂] (E = S, Se, Te), [(MoOCl₃)₂{o-C₆H₄(EMe)₂}]_n (E = Se or Te) and [(MoOCl₃)₂{MeTe(CH₂)₃TeMe}]_n, have been obtained by reaction of the ligands with [MoOCl₃(thf)₂] or MoOCl₃ in either CH₂Cl₂ 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-[MoOCl₃{MeS(CH₂)₃SMe}], mer-[MoOCl₃{ⁱPrS(CH₂)₂SⁱPr}] and mer-[MoOCl₃{MeSe(CH₂)₂SeMe}], as well as the six-coordinate chloride-bridged dimers, [{MoOCl₂(SMe₂)}₂(μ-Cl)₂] and [{MoOCl₂(SeMe₂)}₂(μ-Cl)₂]. The structure of the mixed-valence decomposition product, [Mo^IVCl{o-C₆H₄(TeMe)₂}₂(μ-O)Mo^VOCl₄], was also determined. In toluene solution MoOCl₄ is reduced by MeS(CH₂)₃SMe to produce the Mo(V) complex, [MoOCl₃{ MeS(CH₂)₃SMe}]. Crystal structures of the previously unknown diphosphine analogue, [MoOCl₃{Me₂P(CH₂)₂PMe₂}], and the mixed-valence derivative [Mo^IVCl{Me₂P(CH₂)₂PMe₂}₂(μ-O)Mo^VOCl₄] are also reported for comparison and help to clarify earlier contradictory literature reports. In contrast to the dimeric EMe₂ complexes, [{MoOCl₂(EMe₂)}₂(μ-Cl)₂], PMe₃ forms the monomeric complex, fac-[MoOCl₃(PMe₃)₂].