One‐pot stepwise reductive amination reaction by N‐coordinate sulfonamido‐functionalized Ru(II) complexes in water

Abstract

New complexes of formula [RuCl(p-cymene)(L)] (7-12) were prepared with [RuCl 2 (p-cymene)] 2 and pre-synthesized N-arenesulfonly-o-phenylenediamines(1-6) and characterized using 1 H NMR, 13 C NMR, Fourier transform infrared and UV-visible spectroscopic techniques, and single-crystal X-ray diffraction analysis was performed for one complex (8). Complexes 7-12 were investigated in the reduced imine synthesis reaction (in the presence of HCOONa/HCOOH). The best turnover frequency values were found to be 100 h −1 for 1 and 99 h −1 for 6 in the transfer hydrogenative reductive amination reaction of 4-methoxyaniline and 3,4,5-trimethoxybenzaldehyde. The most important feature of this reaction is that it is an environmental friendly procedure because of being conducted in an aqueous environment. That no organic solvent is used allows one to say that this reaction represents green chemistry.

Half-Sandwich Ru(II) Complexes with N,O-Chelate Ligands: Diverse Catalytic Activity for Amine Synthesis in Water

“…The UV-vis spectra of complexes Ru1 – Ru4 in CH 3 CN solution were characterized in order to investigate the electronic structures and the coordination mode of the metal center. As shown in Figure , the absorption bands around 300–350 nm were assigned to the metal-to-ligand charge transfer (MLCT) n→π* and π→π* transition, and the MLCT dπ→π* transition bands were shown in the range of 400–450 nm . Similar UV-vis spectra of the four ruthenium complexes indicated their structures were analogous with each other.…”

“…As shown in Figure 1, the absorption bands around 300−350 nm were assigned to the metal-to-ligand charge transfer (MLCT) n→π* and π→π* transition, and the MLCT dπ→π* transition bands were shown in the range of 400−450 nm. 28 Similar UV-vis spectra of the four ruthenium complexes indicated their structures were analogous with each other. No peaks were found at approximately 3400 cm −1 in IR spectra of the half-sandwich ruthenium complexes, which may suggest the Ru−O bond formation through the deprotonation of the −OH group.…”

“…For example, Özpozan and co-workers reported transfer hydrogenative RA reactions using a neutral N,N-chelate half-sandwich ruthenium complex as catalyst. But the reaction conversions are not very high and only aldehydes are tolerant in such condition …”

“…But the reaction conversions are not very high and only aldehydes are tolerant in such condition. 28 Due to the diverse catalytic efficiency and good activity of the half-sandwich Ru(II) complexes, the investigation of the synthesis and application of this type of complex with a novel structure is interesting and valuable. Herein, we reported four types of N,O-chelate half-sandwich Ru(II) complexes containing a β-ketoamino motif.…”

Half-Sandwich Iridium Complexes Based on β-Ketoamino Ligands: Preparation, Structure, and Catalytic Activity in Amide Synthesis

“…The absorption bands in the range of 350−380 nm were attributed to the metal-to-ligand charge-transfer (MLCT) n → π* and π → π* transitions, and other absorption bands exhibited around 430−480 nm were assigned to the MLCT dπ → π* transition bands of the iridium complexes. 33 All of the iridium complexes showed similar UV−vis spectra, which indicated their similar structures. Crystal Structure of the Iridium Complex 3 (CCDC 2085201).…”