DEOXYGENATION OF OXOVANADIUM(IV) COMPLEXES UNDER MILD CONDITIONS - CONVERSION OF VANADYL SPECIES TO THE CORRESPONDING DIHALIDES WITH CARBOXYLIC-ACID HALIDES

A new procedure for the deoxygenation of VO2+ complexes utilizing carboxylic acid halides in toluene or methylene chloride has been successfully applied to several vanadyl complexes with different ligand types. Facile conversion of vanadyl beta-diketonates, dialkyldithiocarbamates, beta-ketiiminates, 8-quinolinolate and porphyrin complexes to the corresponding dihalide complexes has been achieved, demonstrating the general application of the synthetic method. The beta-diketonate complexes were studied in the greatest detail. VX2(Y)2 (X = Cl, Br; Y = CH3COCHCOCH3, CH3COCHCOC6H5) were synthesized in high yield, and the single-crystal X-ray structure of VCl2(CH3COCHCOCH3)2 was obtained. The structure contains a mononuclear unit with trans-chloride ligands and distorted octahedral symmetry. The complexes were examined by IR; the spectra exhibited the characteristic loss of the V=O band at approximately 1000 cm-1. For VX2(CH3 COCHCOCH3)2 the ligand bands indicate more delocalization of charge onto the ligands compared with the vanadyl starting material, which is consistent with the trans octahedral geometry of VCl2(CH3COCHCOCH3)2 and its co-planar chelate ligands. The UV vis spectra show a weak maximum around 600-700 nm with epsilon(m) of approximately 2000 dm3 mol cm-1, typical of dihalogenated complexes.