Some tertiary phosphine and tertiary arsine complexes of molybdenum-(II), molybdenum(IV), tungsten(II), and tungsten(IV)

Abstract

Halogen oxidation of complexes of the type cis-[M(CO)₄L₂], (M = Mo or W; L = PEt₃, PMe₂Ph, or AsMe₂Ph) gives seven-co-ordinate complexes, [MX₂(CO)₃L₂](X = Cl, Br, or I). The yellow complex [MoBr₂(CO)₃(PEt₃)₂] loses carbon monoxide reversibly to give a blue complex [MoBr₂(CO)₂(PEt₃)₂]. Chlorine oxidation of cis-[Mo(CO)₄(PMe₂Ph)₂] gives [Mo₂Cl₂(CO)₄(PMe₂Ph)₄] and the complexes [MoX₂(CO)₃(PMe₂Ph)₂](X = Br or I) on heating readily give [Mo₂X₂(CO)₄(PMe₂Ph)₄]. Halogen oxidation of complexes of the type fac-[M(CO)₃L₃] generally gives unidentified products. Treatment of [WBr₂(CO)₄] with PMe₂Ph (two mole per tungsten atom) gives [WBr₂(CO)₃(PMe₂Ph)₂]. Halogenocarbonyls of type [MX₂(CO)₄](M = Mo or W; X = Cl or Br) with three moles of PMe₂Ph give complexes of type [MX₂(CO)₂(PMe₂Ph)₃]. Treatment of complexes of type cis-[M(CO)₄L₂](M = Mo or W; L = PMe₂Ph or PEt₂Ph) with an excess of bromine or chlorine (X₂) gives complexes of type trans-[MX₄L₂]. The paramagnetic complexes [WX₄(PMe₂Ph)₂](X = Cl or Br), take up one mole of PMe₂Ph reversibly to give paramagnetic seven-co-ordinate complexes of type [WX₄(PMe₂Ph)₃]. The magnetic moments of the compounds trans-WCl₄(PMe₂Ph)₂] and [WCl₄(PMe₂Ph)₃],½C₆H₆ over the temperature range 90–300°K are given and discussed. The ¹H n.m.r. spectra of these tungsten(IV) complexes show narrow lines and the resonances have abnormal chemical shifts owing to contact and/or pseudocontact interactions of the unpaired electrons. N.m.r. and i.r. data [ν(CO) and ν(M–Cl)] are given and discussed.