Syntheses, structures, and catalytic investigation of dicationic ruthenium(II)-CNC pincer complexes with multiple NHCs donor ligands

Abstract

We report the reactivity of cationic Ru(II) pincer complexes [Ru(CNCMe)(CNMe)I]PF<inf>6</inf> (1a), [Ru(CNCi-Pr)(CNMe)I]PF<inf>6</inf> (1b) and [Ru(CNCCy)(CNMe)I]PF<inf>6</inf> (1c) with CH<inf>3</inf>CN and PPh<inf>3</inf> ligands and afforded dicationic Ru(II)-CNC pincer complexes namely, [Ru(CNCMe)(CNMe)CH<inf>3</inf>CN]2PF<inf>6</inf> (2a), [Ru(CNCi-Pr)(CNMe)CH<inf>3</inf>CN]2PF<inf>6</inf> (2b), [Ru(CNCCy)(CNMe)CH<inf>3</inf>CN]2PF<inf>6</inf> (2c), [Ru(CNCMe)(CNMe)PPh<inf>3</inf>]2PF<inf>6</inf> (3a), [Ru(CNCi-Pr)(CNMe)PPh<inf>3</inf>]2PF<inf>6</inf> (3b) and [Ru(CNCCy)(CNMe)PPh<inf>3</inf>]2PF<inf>6</inf> (3c). All the new complexes were characterized spectroscopically by multinuclear NMR and HRMS, and molecular structures of complexes 2a and 3a have been determined by the single-crystal X-ray diffraction technique. The structures and electronic properties of all complexes are probed through UV–vis and electrochemical investigations for a comparison of ancillary ligand effects. Investigation of the catalytic activity of new complexes towards nitrile hydration reveals that the reaction proceeds through a common Ru-OH intermediate generated by removal of the I−, CH<inf>3</inf>CN, or PPh<inf>3</inf> ligands, and I− based catalysts (1a-c) are more active than those with CH<inf>3</inf>CN (2a-c) and PPh<inf>3</inf> (3a-c) ligands. © 2025 Elsevier B.V., All rights reserved.