Neutral and cationic ruthenium carbonyl complexes [Ru(CO)(2,2′-dipyridylamine)(PR3)Cl2] and [Ru(CO)(N-N)(PPh3)2(H)]Cl: synthesis, structural characterization and transfer-hydrogenation

The neutral complexes [Ru(CO)(dpa)(PR3)Cl-2] (R = Ph (1) or p-tol (2); dpa = 2,2'-dipyridylamine) were synthesized by the reaction of [Ru(CO)(dmf)(PR3)(2)Cl-2] (dmf = N,N-dimethylformamide) and the dpa ligand, while the cationic carbonyl hydride complexes [Ru(CO)(N-N)(PPh3)(2)(H)]Cl were synthesized by reaction of [Ru(CO)(PPh3)(3)Cl(H)] and the appropriate N-N ligand [N-N = 2,2'-bipyridine = bipy (3), 2,2'-4,4'dimethyl-bipyridine = dmb (4) and 2,2'-dipyridylamine = dpa (5)]. The complexes were characterized by NMR (P-31, H-1 and HMBC H-1-P-31), FTIR, elemental analysis and X-ray diffraction. The molecular structure of [Ru(CO)(dpa)(PPh3)Cl-2] (1) was determined by X-ray crystallography. The crystal packing is stabilized by strong (CH3)O-H center dot center dot center dot Cl and N-H center dot center dot center dot OH(CH3) hydrogen bonds between symmetry-related molecules leading to the formation of dimers. Complexes 1-6 were evaluated as pre-catalysts for the reduction of acetophenone under transfer-hydrogenation conditions using isopropanol as hydrogen source, and conversions up to 86 % in 4 h were achieved.