The use of X-ray photoelectron spectroscopy to assign formal oxidation states in complexes of tungsten (vi), (v) and (iv)

Abstract

X-ray photoelectron spectra of {[WCl 4(NPh)] 2}, WCl 4(O) and the η 2-acetylene complex {[WCl 4(η 2-PhC 2Ph)] 2}show W 4f 7/2 binding energies (35.8, 37.0 and 35.1 eV, respectively) which are consistent with a formal oxidation state of W(vi). [WCl 2(NPh)(NCMe 3)(bipy)] and [WCl 2(O)(CHC{CH 3} 3)(PMe 3) 2] (binding energies 34.2 and 34.1 eV) are also W(vi). The imido complexes [WCl 3(NPh)(PMe 3) 2], {WCl 3[NC 6H 3( Pr 2 i )-2,6](PMe 3) 2}, {WCl 3[NC 6H 3( Pr 2 i )-2,6](dmbipy)} and the η 2-acetylene complexes [WCl 3(η 2-PhC 2Ph)(PMe 3) 2] and [WCl 3(η 2-PhC 2Ph)(PMe 2Ph) 2] have binding energies in the range 33.6–34.2 eV consistent with tungsten (v). Imido complexes [WCl 2(NPh)(PMe 3) 3],[BPh 4][WCl(NPh)(MeCN)(PMe 3) 2], [WCl 2(NPh)(L)(PMe 3) 3] (L = Me 2CCH 2, PhC 2Ph), {WCl 2[NC 6H 3(Pr i) 2-2,6](PhC 2H)(PMe 3) 2], {WCl 2[NC 6H 3(Pr i) 2-2,6](PhC 2Ph)(dmbipy)] and [WCl 2(NCMe 3)(PhC 2Ph)(bipy)] have binding energies in the range 32.5–34.0 eV consistent with W(iv). The η 2-nitrile complex [WCl 2(η 2-NCC 6H 4Me-4)(PMe 3) 3] (binding energy 32.9 eV) is also W(iv). The range of binding energies for the complexes [WCl 4(P) 2] (P = PMe 3, PMe 2Ph and PEt 3) and [WCl 4(PMe 3) 3] which are more obviously W(iv) is 33.5–34.4 eV. The η 2-acetylene complexes [WCl 2(η 2-PhC 2Ph)(L)(PMe 3) 2] (L = PMe 3, CH 2CH 2 and CO) and [WCl 2(η 2-PhC 2Ph)(CO)(PMe 2Ph) 2] have binding energies (range 32.7–33.8 eV) consistent with W(iv). The range of W 4f 7/2 binding energies for these complexes confirms that the electron withdrawing properties of ligands are more important in determining core electron level energies than structural considerations.