Half-sandwich ruthenium-carbene catalysts: Synthesis, characterization, and catalytic application in the N-alkylation of amines with alcohols

In this study, the synthesis and characterization of new half-sandwich ruthenium complexes containing oxygen functionalised N-aryl and N-alkyl benzimidazol-2-ylidene ligands have been reported. All ruthenium complexes were tested as catalysts for a wide range of substrates in the N-alkylation of secondary cyclic amines such as pyrrolidine and piperidine, and 4-methylaniline which was a primary aromatic amine with alcohols by hydrogen-borrowing process. The catalytic reactions were performed with 1 mol% catalyst loading at 120 degrees C, 16 h under solvent-free conditions. All ruthenium complexes showed excellent catalytic activity, and N-alkylated products were obtained selectively.