Vanadyl tetradentate Schiff base complexes as catalyst for C-H bond activation of olefins with tert-butylhydroperoxide: Synthesis, characterization and structure

摘要

Three N2O2 tetradentate Schiff base ligands (H2L1-3) were prepared by reaction of 1,2-propylenediamine and appropriate aldehyde and ketone and characterized by FT-IR, H-1 and C-13 NMR. The vanadyl complexes were synthesized by treating an ethanolic solution of the appropriate ligand and one equivalent of VO(acac)(2) to yield VOL1-3. These oxovanadium (IV) complexes were characterized on the basis of their FT-IR, UV-Vis spectroscopy and elemental analysis. The crystal structure of VOL3 has been determined. The metal center in VOL3 is a deformed tetragonal pyramidal N2O3 coordination sphere. These complexes are used as catalyst for the selective epoxidation of olefins. High selectivity of epoxidation for cyclooctene observed from oxidation data. The catalytic activity increases as the number of electron-donor groups increases, and the catalytic selectivity is varied by changing the substituents on the ligands. The catalytic system described here is an efficient and inexpensive method for the oxidation of olefins, with the advantages of high activity, selectivity, re-usability and short reaction time. (C) 2007 Elsevier B.V. All rights reserved.