Synthesis of rhodium(III) complexes with tris/tetrakis‐benzimidazoles and benzothiazoles—quick identification of cyclometallation by nuclear magnetic resonance spectroscopy

Abstract

] (X = Cl, Br, I). Elemental analysis, IR and 1 H nuclear magnetic resonance (NMR) chemical shifts supported the binuclear nature of the complexes. Cyclometallation was detected by conventional 13 C NMR spectra that showed a doublet around ∼190 ppm. Cyclometallation was also detected by gradient-enhanced heteronuclear multiple bond correlation (g-HMBC) experiment that showed cross-peaks between the cyclometallated carbon and the central benzene ring protons of 1-3. Cyclometallation was substantiated by two-dimensional 1 H-1 H correlated experiments (gradiant-correlation spectroscopy and rotating frame Overhauser effect spectroscopy) and 1 H-13 C single bond correlated two-dimensional NMR experiments (gradient-enhanced heteronuclear single quantum coherence). The 1 H-15 N g-HMBC experiment suggested the coordination of the heterocycles to the metal ion via tertiary nitrogen.

Liquid-phase catalytic oxidation of organic substrates by a recyclable polymer-supported copper(II) complex

“…Transition metal complexes based on nitrogen heterocycles with benzimidazole rings have been studied extensively [1][2][3][4][5]. Some of the Cu(II) complexes show good catalytic activity, particularly toward the synthetically important oxidation of substituted phenols [6].…”