Ru(II)‐Complexes of Pyridyl Functionalized N‐Heterocyclic Carbene Ligands: Novel Catalysts for CN Bond Formation Using Hydrogen Autotransfer Strategy

A series of pyridine‐based unsymmetrical 1,3 disubstituted benzimidazolium bromides have been synthesized as N‐heterocyclic carbene (NHC) precursors. These compounds have been used for the synthesis of three novel pyridyl–NHC complexes— Ru–Py–CH 3 , Ru–Py–CF 3 , and Ru–Py–H— which have been characterized. The complexes have been observed to be air‐stable and show catalytic activity toward the N‐alkylation of amines using alcohols under air. Notably, Ru–Py–CH 3 has been found to be very efficient toward the N‐alkylation of various amines at 0.75 mol% loading, activated by 20 mol% NaO t Bu. A large variety of amines are converted to secondary amines with good yield on coupling aromatic and aliphatic alcohols. Detailed control experiments and mechanistic pathway studies are provided to offer more insights into the reaction mechanism, which has been found to follow a green hydrogen autotransfer pathway.