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 [RuCl2(arene)(NHC)], (arene = η6‐p‐cymene). The structures of all compounds were characterized by 1H NMR, 13C 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. [ABSTRACT FROM AUTHOR]