Degradation of ionized OV(OCH3)3 in the gas phase. From the neutral compound all the way down to the quasi-terminal fragments VO+ and VOH+.

The consecutive fragmentation of ionized trimethyl vanadate(V), OV(OCH3)3 (1), is examined by experiment and theory. After an elimination of formaldehyde from the molecular ion 1+, subsequent dissociations proceed via losses of first H2 and then two molecules of formaldehyde to finally yield the VOH+ cation; these redox reactions involve the V(II)/V(IV) manifold. At elevated energies, expulsion of CH3O* from 1+ can efficiently compete to afford OV(OCH3)2+, a formal V(V) compound, from which subsequent losses of H2 and two units of CH2O lead to bare VO+, thereby exploring the V(III)/V(V) redox manifold. Experiments using complementary mass spectrometric techniques, i.e., neutralization-reionization experiments and ion/molecule reactions, in conjunction with extensive computational studies provide deep insight into the ion structures and the relative energetics of these dissociation reactions. In particular, a quantitative energetic scheme is obtained that ranges from neutral OV(OCH3)3 all the way down to the quasi-terminal fragment ions VOH+ and VO+, respectively.

Chloride-bridged oxovanadium(V) complexes with alkoxyalkoxide ligands. Synthesis, structure, electrochemistry and reactivities.

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(OCH2CH(2)OMe)]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.