Ruthenium(II)‐(Arene)‐N‐Heterocyclic Carbene Complexes: Efficient and Selective Catalysts for the N ‐Alkylation of Aromatic Amines with Alcohols

A series of unsymmetrical 1,3‐disubstituted benzimidazolium chlorides were synthesized as N‐heterocyclic carbene (NHC) precursors. These compounds were used for synthesis of the new ruthenium(II) complexes of the type [RuCl 2 (arene)(NHC)], (arene = η 6 ‐ p ‐cymene). The structures of all compounds were characterized by 1 H NMR, 13 C NMR and FT‐IR spectroscopy techniques. The catalytic activity of the ruthenium complexes has been evaluated with respect to the mono‐ N ‐alkylation reactions of aromatic amines with various alcohol derivatives under solvent‐free conditions at 120 °C using the borrowing hydrogen strategy.