From vanadium(V) to vanadium(IV) - and backwards

Abstract

With bidentate alkoxy alkoxide and alkoxy alcohol ligands, respectively, a series of oxovanadium complexes in the oxidation state +4 is synthesized starting from oxovanadium(V) compounds. The reaction of two or more equivalents of 2-methoxyethanol with VOCl 3 in n-hexane yields a mixture of the monomeric oxovanadium(IV) complex cis-[VOCl 2 (HOCH 2 CH 2 OMe-κ 2 O)(HOCH 2 CH 2 OMe-κO 1 )] and the alkoxide-bridged oxovanadium(IV) dimer syn-[VOCl(μ-OCH 2 CH 2 OMe-κ 2 O)] 2 , which are separated by fractionated crystallization. The same reaction with 2-ethoxy-and 2-iso-propoxyethanol gives only the alkoxide-bridged oxovanadium(IV) dimers anti-[VOCl(μ-OCH 2 CH 2 OR-κ 2 O)] 2 (R = Et, i Pr). All alkoxide-bridged oxovanadium(IV) dimers are furthermore obtained as decomposition products of the chloride-bridged oxovanadium(V) complexes [VO(μ-Cl)Cl(OCH 2 CH 2 OR-κ 2 O)] 2 (R = Me, Et, i Pr) by Cl 2 elimination and react inversely with Cl 2 to the vanadium(V) compounds. Scheme 1 Chloro oxovanadium(IV) alkoxides with square pyramidal coordination sphere.Fig. 4 Side view of syn-[VOCl(μ-OCH 2 CH 2 OMe-κ 2 O)] 2 2 (left) and anti-[VOCl(μ-OCH 2 CH 2 OEt-κ 2 O)] 2 3 (right) along the V-O-V-O plane.

Crystal structure of bis[μ-2-(diisopropylphosphoryl)propan-2-olato-κ3O1,O2:O1]bis[chloridooxidovanadium(IV)]

“…The Addison -parameter (Addison et al, 1984), as calculated by À0.01667Á(139.45)+0.01667Á(148.82) = 0.156, also points to this coordination (a value of 0 refers to an ideal squarepyramidal, a value of 1 to an ideal trigonal-bipyramidal coordination). The V O double-bond length of 1.586 (2) Å is in the typical range of those reported in similar dimeric oxidochlorido-vanadium(IV) complexes containing alkoxide bridges (Cui et al, 2010;Crans et al, 1991;Foulon et al, 1993;Janas et al, 1997;Rosenthal, 2009).…”