N-Alkylation and N-Methylation of Amines with Alcohols Catalyzed by Nitrile-Substituted NHC–Ir(III) and NHC–Ru(II) Complexes

[Image: see text] A series of nitrile-modified N-heterocyclic carbene (NHC) complexes of Ir(III) (2a–e) and Ru(II) (3a–d) have been prepared by transmetallation of [IrCp*Cl(2)](2) and [RuCl(2)(p-cymene)](2) forming an in situ NHC–Ag complex. The structures of all complexes were characterized by (1)H NMR, (13)C NMR, and Fourier transform infrared (FT-IR) spectroscopies. And the structures were clearly elucidated by performing X-ray diffraction studies on 2b, 3a, and 3c single crystals. The complexes of NHC–Ir(III) (2a–e) and NHC–Ru(II) (3a–d) were investigated in the N-alkylation reaction of aniline derivatives with benzyl alcohols to form N-benzyl amines and in the N-methylation reaction of aniline derivatives with methanol. Both reactions were performed in solvent-free media. The Ir(III) complexes (2a–e) were found to perform essentially better than similar Ru(II) complexes (3a–d) in the N-alkylation and N-methylation reactions. Among the Ir(III) complexes (2a–e), the best results were obtained with 2b. The catalytic mechanisms of both reactions were revealed by (1)H NMR study. Formation of Ir-hydride species was observed for both reactions. This new report provides useful information to evaluate the activity of complexes and the differences in sensitivity between the NHCs.