Synthesis, Molecular Structure, and Olefin Polymerisation Activity of an Oxovanadium(V) Alkoxide with Unprecedented Chloride Bridging Ligands

Abstract

The reaction of 2‐methoxyethanol or (2‐methoxyethanolato)lithium with VOCl3 yields the chloro‐bridged dinuclear complex [VOCl2(OCH2CH2OCH3)]2, which has been characterised spectroscopically and structurally by single‐crystal X‐ray diffraction analysis. This is the first reported structure of a neutral dinuclear oxovanadium complex connected by bridging chloro ligands. The orange complex is a precatalyst for the polymerisation of ethene and the oligomerisation of styrene. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Coordination Chemistry and Applications of Vanadium Alkoxides in Catalysis

“…Therefore a promoter has been employed for further studies. Indeed yields for dimeric methyl derivative 2 as precatalyst with methyl alumoxan (MAO) as cocatalyst and MTCA as promoter lie at significantly higher values-quantitative conversion is already reached at room temperature, but low molecular masses show that only styrene oligomers have been obtained (2). In opposition to the promoter-free reactions the catalytic activity decreases with rising temperatures.…”

“…The ligands studied ( Figure 1) were chosen because of their proposed ability to stabilize the obtained vanadium compounds in their high oxidation states by forming chelating structures with the additional oxygen donor when complexed to vanadium. With this approach we were able to synthesize compound classes, which were previously inaccessible and to prove their existence by single crystal x-ray diffraction (2)(3)(4). The presence of remaining chloride ligands in the mixed alkoxo chloro complexes obtained makes the metal atom functionalizable e.g.…”

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

“…DOI: 10.1039/b505750g Methyl ether derivative 1 has been synthesised by HCl elimination previously but only in very poor yields. 11 Formation of a blue oily precipitate during the course of reaction indicates that reduction of vanadium(V) to vanadium(IV) had taken place. If the same reaction is carried out in pure dichloromethane as a solvent no product containing crystalline vanadium(V) could be isolated even at low temperatures due to the high solubility of the product in this solvent.…”

“…On the other hand the oxygen containing ligand still has an effect on the polymerisation reaction as simple VOCl 3 shows an explicitly lower activity in direct comparison. 11 Gel permeation chromatography (GPC) analyses prove the formation of high molecular weight polyethene but with very broad molecular mass distribution. All catalysts, except 2 and 3, produce bimodal polymers under the applied conditions.…”

“…First catalytic studies showed mixed alkoxo chloro oxovanadium(V) complexes with ether-alkoxide ligands to be active catalysts in olefin polymerisation. 3,11 The activation of vanadium pre-catalysts requires the addition of main-group-metal alkyls to produce metal-carbon bonds. Thus, oxovanadium complexes originally present as the pre-catalyst react via poorly defined pathways to produce unidentified, catalytically active species.…”