Application of polymer-bound Cu(II) complex of 2-phenylbenzimidazole towards oxidative bromination and oxidative esterification of organic substrates

Abstract

Application of polymer immobilized Cu(II)(PS-Cu(II)PBMZL) complex of 2-phenylbenzimidazole in oxidative bromination and oxidative esterification of organic compounds is reported. The complex has been characterized by CHNS analysis, UV-Vis/DRS, FT-IR, ESR spectroscopic studies, magnetic moment measurements and TG analysis. A shift in νC=N in the polymer-bound complex compared with the ligand indicates its complexation to Cu(II) center. A distorted octahedral coordination of Cu(II) in PS-Cu(II)PBMZL is confirmed by the electronic spectral data and the efficient binding of PBMZL is ascertained by adecrease in the intensity of νCH2Cl peak in the PS-PBMZL compared to the polymer support. An array of experiments has been carried out to assess the influence of various reaction parameters on the performance of PS-Cu(II)PBMZL. The activity of the polymer-bound complex is higher than the unbound complex. In the case of oxidative bromination, PS-Cu(II)PBMZLH displayed a 65% phenol conversion with 61% 2-bromophenol selectivity. The % benzaldehyde conversion and methyl benzoate selectivity in the case of oxidative esterification has been found to be 79 and 82%. Compiling all these results along with the knowledge obtained regarding the most probable reactive species, tentative mechanisms have been proposed.