A pentanuclear Er (III) coordination cluster as a catalyst for selective synthesis of 1,2‐disubstituted benzimidazoles
Arijit Sarkar, Sourav Jana, Hari Pada Nayek
Abstract
A new tridentate ligand ( H 3 L ) was prepared from the reaction of 6‐formyl‐2‐(hydroxymethyl)‐4‐ tert ‐butylphenol and 2‐amino‐4‐nitrophenol. The ligand H 3 L and acetylacetone were treated with Er (NO 3 ) 3 ·5H 2 O, which resulted in the formation of a pentanuclear coordination cluster [Er 5 (LH) 4 (acac) 4 ( μ 3 ‐O)( μ 3 ‐OH)(H 2 O) 2 ] . 5H 2 O ( 1 ) (acac = acetylacetonate). Five Er (III) ions are arranged in a nonlinear fashion in 1 . Complex 1 was utilized as a catalyst towards the selective synthesis of 1,2‐disubstituted benzimidazole derivatives involving o ‐phenylenediamine and different aldehydes. Yields of 1,2‐disubstituted benzimidazole derivatives were in the range of 66%–91%. This study demonstrates the first‐ever approach to employ a homo‐ and pentanuclear lanthanide coordination cluster for catalyzing the synthesis of 1,2‐disubstituted benzimidazoles.