Crystal structure, electrochemistry, and catalytic studies of a series of new oxidovanadium(IV) Schiff-base complexes derived from 1,2-diphenyl-1,2-ethylenediamine

New derivatives of N 2 O 2 tetradentate Schiff bases, from condensation of meso-1,2-diphenyl-1,2-ethylenediamine and salicylaldehyde derivatives (X-salicylaldehyde; X = 3-OMe, 4-OMe, 5-OMe, 6-OMe, 5-Cl, 5-Me), and oxidovanadium(IV) complexes were synthesized and characterized by 1 H NMR, UV-Vis, IR...

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Bibliographic Details
Published in:Journal of coordination chemistry Vol. 65; no. 5; pp. 840 - 855
Main Authors: Ghaffari, Abolfazl, Behzad, Mahdi, Dutkiewicz, Grzegorz, Kubicki, Maciej, Salehi, Mehdi
Format: Journal Article
Language:English
Published: Abingdon Taylor & Francis Group 10.03.2012
Taylor & Francis Ltd
Subjects:
Catalysis
Catalysts
Catalytic activity
Crystal structure
Derivatives
Epoxidation
Oxidants
Oxidovanadium(IV)
Schiff base
Solvents
Tetradentate
ISSN:0095-8972, 1029-0389
Online Access:Get full text
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Summary:New derivatives of N 2 O 2 tetradentate Schiff bases, from condensation of meso-1,2-diphenyl-1,2-ethylenediamine and salicylaldehyde derivatives (X-salicylaldehyde; X = 3-OMe, 4-OMe, 5-OMe, 6-OMe, 5-Cl, 5-Me), and oxidovanadium(IV) complexes were synthesized and characterized by 1 H NMR, UV-Vis, IR spectroscopy, and elemental analysis. Crystal structure of 5-OMe; H 2 L 3 and two of the complexes (VOL 2 and VOL 3 ) were also obtained. In the crystals, the molecule of H 2 L 3 is C i symmetrical, as it occupies the special position on the center of symmetry; its conformation is partially determined by classical intramolecular O-H···N hydrogen bonds. The complexes have monomeric structures with a distorted square pyramid of vanadium, with the oxo ligand in the apical position. Cyclic voltammetry studies show quasi-reversible V IV /V V redox for which the presence of electron-withdrawing groups on salicylaldehyde derivatives shifts the E° to more positive values. The complexes were used as catalysts for selective epoxidation of cyclooctene with tert-butylhydroperoxide as oxidant, in various solvents and reaction conditions. High catalytic activities and excellent selectivity was found. The catalytic activity of the complexes increased increasing E°, a consequence of the presence of electronegative substituents. This epoxidation process with the new catalysts was also studied under solvent-free condition and excellent reactivity was observed.
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ISSN:0095-8972
1029-0389
DOI:10.1080/00958972.2012.662275