B. Mondal, M. Drew, T. Ghosh
Jul 1, 2009
Citations
0
Influential Citations
31
Citations
Journal
Inorganica Chimica Acta
Abstract
[V IV O(acac) 2 ] reacts with an equimolar amount of benzoyl hydrazone of 2-hydroxyacetophenone (H 2 L 1 ) or 5-chloro-2-hydroxyacetophenone (H 2 L 2 ) in the presence of excess pyridine (py) in methanol to produce the quaternary [V V O(L 1 )(OCH 3 )(py)] ( 1 ) and [V V O(L 2 )(OCH 3 )(py)] ( 2 ) complexes, respectively, while under similar condition, the benzoyl hydrazones of 2-hydroxy-5-methylacetophenone (H 2 L 3 ) and 2-hydroxy-5-methoxyacetophenone (H 2 L 4 ) afforded only the methoxy bridged dimeric [V V O(L 3 /L 4 )(OCH 3 )] 2 complexes. The X-ray structural analysis of 1 and 2 indicates that the geometry around the metal is distorted octahedral where the three equatorial positions are occupied by the phenolate-O, enolate-O and the imine-N of the fully deprotonated hydrazone ligand in its enolic form and the fourth one by a methoxide-O atom. An oxo-O and a pyridine-N atom occupy two axial positions. Quaternary complexes exhibit one quasi-reversible one-electron reduction peak near 0.25 V versus SCE in CH 2 Cl 2 and they decompose appreciably to the corresponding methoxy bridged dimeric complex in CDCl 3 solution as indicated by their 1 H NMR spectra. These quaternary VO 3+ complexes are converted to the corresponding V 2 O 3 4 + -complexes simply on refluxing them in acetone and to the VO 2 + -complexes on reaction with KOH in methanol. An equimolar amount of 8-hydroxyquinoline (Hhq) converts these quaternary complexes to the ternary [V V O(L)(hq)] complexes in CHCl 3 .