2-TETRAHYDROFURFUROXO-VANADIUM-(III) AND 2-TETRAHYDROFURFUROXO-VANADIUM-(IV) COMPLEXES - SYNTHESIS, STRUCTURE AND REACTIVITIES OF (2)(MU,ETA(2)-THFFO)(4)CL-4]CENTER-DOT-2CH(2)CL(2) AND [V-2(MU,ETA(2)-THFFO)CL2O2]

Vanadium complexes of 2-tetrahydrofurfuroxide (2-tetrahydrofurylmethox ide) (thffo) with the metal in oxidation state III and IV have been pr epared and characterized. The reaction of [VCl3(thf)(3)] with 1.5 equi valents of [Mg(thffo)(2)] in tetrahydrofuran (thf) or CH2Cl2 led to th e formation of 2(mu(3),eta(2)-thffo)(2)(mu,eta(2)-thffo)(4)Cl-4]. 2CH( 2)Cl(2) 1. Its structure consists of centrosymmetric tetranuclear mole cules and CH,CI, of crystallization. Two Mg and two V atoms have disto rted octahedral geometry and form a nearly regular Mg2Vw rhombus. The V...V distance is 3.266(2) Angstrom. The reaction of [VOCl2(thf)(2)] w ith Na(thffo) in thf yielded [V-2(mu,eta(2)-thffo)(2)Cl2O2] 2. Two VOC I units are linked by alkoxide oxygen bridges. The V...V distance is 3 .070(1) Angstrom. Compounds 1 and 2 are very effective procatalysts fo r the polymerization of ethylene.