Synthesis, spectroscopic and structural characterisation of vanadium(IV) and oxovanadium(IV) complexes with arsenic donor ligands

The reaction of o-C6H4(AsMe2)2 with VCl4 in anhydrous CCl4 produces orange eight-coordinate [VCl4{o-C6H4(AsMe2)2}2], whilst in CH2Cl2 the product is the brown, six-coordinate [VCl4{o-C6H4(AsMe2)2}]. In dilute CH2Cl2 solution slow decomposition occurs to form the VIII complex [V2Cl6{o-C6H4(AsMe2)2}2]. Six-coordination is also found in [VCl4{MeC(CH2AsMe2)3}] and [VCl4{Et3As)2]. Hydrolysis of these complexes occurs readily to form vanadyl (VO2+) species, pure samples of which are obtained by reaction of [VOCl2(thf)2(H2O)] with the arsines to form green [VOCl2{o-C6H4(AsMe2)2}], [VOCl2{MeC(CH2AsMe2)3}(H2O)] and [VOCl2(Et3As)2]. Green [VOCl2(o-C6H4(PMe2)2}] is formed from [VOCl2(thf)2(H2O)] and the ligand. The [VOCl2{o-C6H4(PMe2)2}] decomposes in thf solution open to air to form the diphosphine dioxide complex [VO{o-C6H4(P(O)Me2)2}2(H2O)]Cl2, but in contrast, the products formed from similar treatment of [VCl4{o-C6H4(AsMe2)2}x] or [VOCl2{o-C6H4(AsMe2)2}] contain the novel arsenic(V) cation [o-C6H4(AsMe2Cl)(µ-O)(AsMe2)]+. X-ray crystal structures are reported for [V2Cl6{o-C6H4(AsMe2)2}2], [VO(H2O){o-C6H4(P(O)Me2)2}2]Cl2, [o-C6H4(AsMe2Cl)(µ-O)(AsMe2)]Cl·[VO(H2O)3Cl2] and powder neutron diffraction data for [VCl4{o-C6H4(AsMe2)2}2].Graphical abstractComplexes of vanadium tetrachloride and vanadium oxide dichloride with a range of arsenic donors are reported, and their spectroscopic and structural characterisation described