Oxorhenium(V) complexes with 1H-benzimidazole-2-carboxylic acid - Synthesis, structural characterization and catalytic application in epoxidation reactions

Depending on the experimental conditions three novel oxorhenium(V) complexes incorporating 1H-benzimidazole-2-carboxylic acid (2-bimH) cis-Cl,Cl-[ReOCl2(2-bim)(PPh3)] (1), cis-Br,Br-[ReOBr2 (2-bim)(PPh3)] (2) and [ReOCl(2-bim)(2)] (3) were synthesized. The reported complexes were characterized by spectroscopic methods (IR, H-1, C-13, P-31 NMR, UV-Vis, ESI+-MS), cyclic voltammetry and single crystal X-ray diffraction analysis. To elucidate the structural, spectroscopic and bonding properties, calculations at the DFT level were undertaken. The catalytic competencies of compounds 1-3 were investigated in the epoxidation of cyclooctene with tert-butyl hydroperoxide (TBHP) as oxidant. The studies revealed higher catalytic activities for complexes based on one 1H-benzimidazole-2-carboxylic acid (compounds 1 and 2) and phosphine as ancillary ligand, with the yield of cyclooctane-oxide varying between 60% and 64% (50 degrees C, 24 h). (C) 2013 Elsevier Ltd. All rights reserved.