Catalytic transfer hydrogenation of ketones by ruthenium(II) cyclometallated complex containing para-chloroacetophenone thiosemicarbazone

Ruthenium(II) cyclometallated complex containing para-chloroacetophenone thiosemicarbazone (L) of formula [Ru(L)(CO)(PPh3)2] has been synthesized and characterized by elemental and spectral analyses. The thiosemicarbazone ligand coordinates to ruthenium as a terdentate C, N, and S donor generating two five membered metallacycles. The crystal structure analysis of the complex [Ru(L)(CO)(PPh3)2] indicates the presence of a distorted octahedral geometry. The complex shows a quasi-reversible one electron oxidation (RuIII/RuII) at 0.78 V vs SCE. Further, the catalytic transfer hydrogenation of substituted acetophenones by the titled complex was carried out with conversions up to 99.3% in the presence of i-prOH/KOH.