Synthesis and characterization of ruthenium(II) complexes based on diphenyl-2-pyridylphosphine and their applications in transfer hydrogenation of ketones

Synthesis and characterization of the ruthenium complexes RuH(CO)Cl(κ¹-P-PPh₂Py)₂(PPh₃)] (1) and Ru(CO)Cl₂(κ¹-P-PPh₂Py)(κ²-P-N-PPh₂Py)] (2) containing diphenyl-2-pyridylphosphine (PPh₂Py) are described. Spectral and structural data suggested linkage of the PPh₂Py in κ¹-P bonding mode in 1 and both the κ¹-P and κ²-P-N bonding modes in 2. The complex 1 reacted with N,N-donor bases viz., ethylenediamine (en), N,N′-dimethyl-(ethylenediamine) (dimen), 1,3-diaminopropane (diap), 2,2′-bipyridine (bipy), 1,10-phenanthroline (phen) and di-2-pyridylaminomethylbenzene (dpa) to afford cationic complexes of formulation RuH(CO)(κ¹-P-PPh₂Py)₂(N-N)]⁺ (3-8) N-N = en, 3; dimen, 4; diap, 5; bipy, 6; phen, 7; and dpa, 8], which have been isolated as their tetrafluoroborate salts. The complexes under investigation have been characterized by elemental analyses, spectroscopic and electrochemical studies. Molecular structures of 2, 3, 6, and 8 have been determined by single crystal X-ray diffraction analyses. Further, the complexes 1-8 act as effective precursor catalyst in transfer hydrogenation of acetophenone/ketones in basic 2-propanol.