2-Tetrahydrofurfuroxo-vanadium-(III) and -(IV) complexes. Synthesis, structures and reactivities of [V2Mg2(µ3,δ2-thffo)2(µ,δ2-thffo)4Cl4]· 2CH2Cl2 and [V2(µ,δ2-thffo)2Cl2O2]†

Abstract

Vanadium complexes of 2-tetrahydrofurfuroxide (2-tetrahydrofurylmethoxide) (thffo) with the metal in oxidation state III and IV have been prepared and characterized. The reaction of [VCl₃(thf)₃] with 1.5 equivalents of [Mg(thffo)₂] in tetrahydrofuran (thf) or CH₂Cl₂ led to the formation of [V₂Mg₂(µ₃,η²-thffo)₂(µ,η²-thffo)₄Cl₄]· 2CH₂Cl₂1. Its structure consists of centrosymmetric tetranuclear molecules and CH₂Cl₂ of crystallization. Two Mg and two V atoms have distorted octahedral geometry and form a nearly regular Mg₂V₂ rhombus. The V · · · V distance is 3.266(2) Å. The reaction of [VOCl₂(thf)₂] with Na(thffo) in thf yielded [V₂(µ,η²-thffo)₂Cl₂O₂] 2. Two VOCl units are linked by alkoxide oxygen bridges. The V · · · V distance is 3.070(1) Å. Compounds 1 and 2 are very effective procatalysts for the polymerization of ethylene.