Ruthenium and palladium complexes incorporating amino-azo-phenol ligands: Synthesis, characterization, structure and reactivity

• New amino-azo-phenol complexes of Pd(II) and Ru(II).
• The palladium complexes catalytised C–C, C–N coupling and cyanation reactions.
• Ruthenium catalyzed transfer hydrogen reaction.

The ligands 2-((2-aminophenyl)diazenyl)phenol, HOL1-NH2, 1a; 2-((2-aminophenyl)diazenyl)-5-methylphenol, HOL2-NH2, 1b; and 2-((2-aminophenyl) diazenyl)-5-chlorophenol, HOL3-NH2, 1c, which are abbreviated as HOL-NH2, 1, afforded the complexes of compositions [(OL-NH)Pd(PPh3)], 2, and [(OL-NH)Ru(CO)(PPh3)2], 3, upon reaction with Na2PdCl4 and Ru(CO)3(PPh3)3 respectively. In all the complexes the metals ions, Pd(II) or Ru(II), are coordinated by deprotonated ligand (OL-NH)2− in tridentate (N, N, O) fashion. X-ray structures of [(OL2-NH)Pd(PPh3)], 2b, and [(OL1-NH)Ru(CO)(PPh3)2], 3a, were determined to confirm the molecular structures. The cyclic voltammograms of [(OL-NH)Ru(CO)(PPh3)2] exhibited two quasi reversible oxidative response near 0.25 and 1.12 V vs. SCE. The nature of HOMO as obtained by DFT calculations has been inspected to have an insight into the redox orbitals. The newly synthesized [(OL-NH)Pd(PPh3)], 2a, complexes exhibited catalytic activity toward the Suzuki, Heck, Cyanation and amination reactions. Catalytic activity of complex [(OL1-NH)Ru(CO)(PPh3)2], 3a, was examined for the conversion of ketones to corresponding alcohols by transfer hydrogen reactions.

New amino-azo-phenol complexes of Pd(II) and Ru(II) were synthesized and unequivocally characterized. The palladium complexes exhibited catalytic activities toward C–C, C–N coupling and cyanation whereas the ruthenium complexes are active transfer hydrogen catalyst.Figure optionsDownload as PowerPoint slide