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

X-ray photoelectron spectra of {[WCl4(NPh)](2)), WCl4(O) and the eta(2)-acetylene complex {[WCl4(eta(2)-PhC2Ph)](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). [WCl2(NPh)(NCMe3)(bipy)] and [WCl2(O)(CHC{CH3}(3))(PMe3)(2)] (binding energies 34.2 and 34.1 eV) are also W(vi). The imido complexes [WCl3(NPh)(PMe3)(2)], (WCl3[NC6H3 (Pr-2(i))-2,6](PMe3)(2)), (WCl(3)INC6H3(Pri2)-2,6](dmbipy)) and the eta(2)-acetylene complexes [WCl3(re-PhC2Ph) (PMe3)2] and [WCl3(re-PhC2Ph)(PMe2Ph)(2)] have binding energies in the range 33.6-34.2 eV consistent with tungsten (v). lmido complexes [WCl2(NPh)(PMe3)(3)].[BPh4][WCl(NPh)(MeCN)(PMe3)(2)]. [WCl2 (NPh)(L)(PMe3)(3)] (L = Me2CCH2, PhC2Ph), (WCl2[NC6H3(Pr-i)(2)-2,61(PhC2H)( PMe3)(2)], (WCl2 NC6H3(Pr-i)(2)-2,6] (PhC2Ph)(dmbipy)I and [WCl2(NCMe3)(PhC2Ph)(biPy)] have binding energies in the range 32.5-34.0 eV consistent with W(iv). The eta(2)-nitrile complex [WCl2(eta(2)-NCC6H4Me-4)(PMe3)(3)] (binding energy 32.9 eV) is also W(iv). The range of binding energies for the complexes [WCl4(P)(2)] (P = PMe3, PMe2Ph and PEt3) and [WCl4(PMe3)(3)] which are more obviously W(iv) is 33.5-34.4 eV. The eta(2) -acetylene complexes [WCl2(re-PhC2Ph)(L)(PMe3)2] (L = PMe3, CH2CH2 and CO) and [WCl2(112-PhC2Ph)(CO)(PMe2Ph)(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. (C) 2011 Elsevier Ltd. All rights reserved.