Substituted 2-(2''-pyridyl)benzimidazole palladium(II) complexes as an efficient catalytic system for Suzuki--Miyaura cross-coupling reactions

Abstract

A new series of $N,N$-type 2-(2'-pyridyl)benzimidazole ligands (\textbf{2A}$_{\mathbf{1}}$,\textbf{ 2A}$_{\mathbf{2}}$,\textbf{ 3B}$_{\mathbf{1}}$,\textbf{ 3B}$_{\mathbf{2}}$,\textbf{ 3B}$_{\mathbf{3}}$, and\textbf{ 4C}$_{\mathbf{1}})$ and their Pd(II) complexes (\textbf{5A}$_{\mathbf{1}}$,\textbf{ 5A}$_{\mathbf{2}}$,\textbf{ 6B}$_{\mathbf{1}}$,\textbf{ 6B}$_{\mathbf{2}}$,\textbf{ 6B}$_{\mathbf{3}}$, and\textbf{ 7C}$_{\mathbf{1}})$ were prepared and characterized by conventional spectroscopic methods and elemental analyses. The incorporation of $N$-coordinated benzimidazole complexes of palladium gave high catalytic activity in the Suzuki--Miyaura coupling of aryl halides substrates. After determining the best active catalyst as \textbf{5A}$_{\mathbf{1}}$, bearing the mesityl substituent on the benzimidazole ring with the Pd(II) ion, optimization studies were carried out via changing the substrate, base, time, atmosphere, and the effect of water. The DMF:H$_{2}$O (4/1) and Cs$_{2}$CO$_{3}$ as base were found to be critical for the efficiency of the reaction yield (100{\%}).