Deoxygenation of oxovanadium(IV) complexes under mild conditions: conversion of vanadyl species to the corresponding dihalides with carboxylic acid halides

Abstract

A new procedure for the deoxygenation of VO 2+ 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 β-diketonates, dialkyldithiocarbamates, β-ketiiminates, 8-quinolinolate and porphyrin complexes to the corresponding dihalide complexes has been achieved, demonstrating the general application of the synthetic method. The β-diketonate complexes were studied in the greatest detail. VX 2(Y) 2 (X = Cl, Br; Y = CH 3COCHCOCH 3, CH 3COCHCOC 6H 5) were synthesized in high yield, and the single-crystal X-ray structure of VCl 2(CH 3COCHCOCH 3) 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 VX 2(CH 3COCHCOCH 3) 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 VCl 2(CH 3COCHCOCH 3) 2 and its co-planar chelate ligands. The UV—vis spectra show a weak maximum around 600–700 nm with ε m of approximately 2000 dm 3 mol cm −1, typical of dihalogenated complexes.