Abstract:
A series of left-to-right inequivalent 1,3-disubstituted benzimidazolium halide pro-ligands having the general formula [(BNHCCH2OxMe)-B-R][X] (R = 3-Me-Bn, 3,5-Me-2-Bn, 2,4,6-Me-3-Bn, 2,3,5,6-Me-4-Bn, 2,3,4,5,6-Me-5-Bn, 3,4,5-(OMe)(3)-Bn, or 4-Bu-t-Bn; X = Cl, Br) were synthesized by the alkylation of 1-((3-methyloxetan-3-yl)methyl)benzimidazole. The corresponding Ag complexes, ((BNHCCH2OxMe)-B-R) AgX, were prepared following pro-ligand addition to Ag2O. These compounds were characterized using spectroscopic techniques such as FT-IR, NMR spectroscopy, and single-crystal X-ray diffraction. The solid-state structure of ((3-Me-BnBNHCCH2OxMe))AgCl revealed a linear monomer while [((2,4,6-Me3-BnBNHCCH2OxMe))AgCl](2) was found to exist as a dimer with pseudo trigonal planar geometry about each metal center. The synthesized ((BNHCCH2OxMe)-B-R)AgX complexes were found to be efficient for the addition of carbon dioxide to epoxides to yield value-added cyclic carbonates at ambient pressure. Amongst the investigated complexes, the bimetallic complex [((2,4,6-Me3-BnBNHCCH2OxMe))AgCl](2) was found to be the most active for CO2 insertion, exhibiting favorable activity when compared to known NHC complexes.