The syntheses and structural characterization of methoxido- and ethoxido-vanadium complexes [VOCl2(OMe)(HOMe)2] (1), [VOCl(OMe)2]2 (2), and [{VOCl(OEt)2}2(THF)] (3) are described. The effects of the reactant ratio, starting materials, and reaction media on the formation of the alkoxido oxidovanadium and their molecular structures are reported. Complex 1 was prepared by reaction of VOCl3 with three equiv of MeOH in pentane. In the solid state, each molecule of 1 is linked with four symmetry related molecules through four O–H···Cl interactions resulting in the formation of a 2D infinite network. Reaction of VOCl3 with 2 equiv of NaOMe in pentane yields the dimeric complex 2, which features a pair of methoxido bridges in the molecular structure. In THF, reaction of VOCl3 with 2 equiv of NaOEt results in a very thermolabile [{VOCl(OEt)2}2(THF)] (3), which adopts a butterfly conformation in the molecular structure and features an interesting alkoxido oxidovandium with syn-orientated V=O functionality.Methoxido- and ethoxido-oxidovanadium(V) with different coordination geometry have been synthesized and characterized. Reaction of VOCl3 with 2 equivalents of NaOEt in tetrahydrofuran affords a novel solvent coordinated complex [VOCl(OEt)2]2(THF) (3) with the two V═O moieties syn-oriented in the solid state.

A dichloro oxovanadium(V) alkoxide complex [VOCl2(OCH2CH2OCH2CH2OnBu)] was synthesised by reaction of VOCl3 and 2-(2-butoxyethoxy)ethanol in pentane. It was characterised by IR, 1H, 13C and 51V NMR spectroscopy, mass spectrometry and elemental analysis. Single-crystal X-ray diffraction reveals a monomeric complex with all oxygen atoms of the ligand attached to the overall octahedrally coordinated vanadium atom. This complex exhibits remarkably higher activity than VOCl3 towards ethene polymerisation with diethyl aluminium chloride as co-catalyst and methyl trichloroacetate as promoter. The complex also catalyses the epoxidation of cyclooctene to cyclooctene oxide with tert-butyl hydroperoxide.A dichloro oxovanadium(V) alkoxide complex [VOCl2(OCH2CH2OCH2CH2OnBu)] was synthesised by reaction of VOCl3 and 2-(2-butoxyethoxy)ethanol in pentane. It was characterised by infrared, 1H, 13C and 51V NMR spectroscopy, mass spectrometry, elemental and single-crystal X-ray diffraction analysis. This complex catalyses the polymerisation of ethene and the oxidation of cyclooctene with tert-butyl hydroperoxide.

A series of mixed alkoxyalkoxo chloro complexes of vanadium(V), [VOCl2(OCH2CH2OR)]2 (R = Me, Et, iPr, Bz), [VOCl2(OCMe2CH2OMe)]2 and [VOCl2(OCH2(cyclo-C4H7O)]2, were synthesised and characterised. The title compounds can be obtained either from VOCl3 and the alkoxyalcohols by HCl elimination or from the corresponding lithium alkoxides and VOCl3 by salt metathesis reaction. X-Ray diffraction studies revealed the title compounds to be dimers with chloride bridging ligands and intramolecular ether coordination. Electrochemical results obtained by cyclic voltammetry indicate irreversible, reductive behaviour. The interactions of the title compounds with oxygen, nitrogen and phosphorus donor ligands were examined. Phosphorus and nitrogen donors lead to reduction products whereas tetrahydrofuran coordinates to the vanadium(V) centre by breaking the chloride bridge. All tetrahydrofuran complexes, [VOCl2(OCH2CH2OR)(thf)] (R = Me, Et, iPr) and [VOCl2(OCMe2CH2OMe)(thf)], have been characterised by single-crystal X-ray diffraction. The solid-state structures of these complexes show that they consist of six-coordinate monomers. Reaction of [VOCl2(OCH2CH2OMe)]2 with Me3SiCH2MgCl gave [VO(CH2SiMe3)3], which has been structurally characterised. The compounds were tested as catalysts for epoxidation and polymerisation reactions. They convert unfunctionalised olefins into the corresponding epoxides with moderate activity. They are good pre-catalysts for the polymerisation of ethene and oligomerise 1-hexene.