Synthesis and catalytic activity of ruthenium(II) complexes containing pyridine-based tridentate triamines (′NNN⌢⌢′) and pyridine carboxylate ligands (NO⌢)

The reaction of [(p-cymene)RuCl2]2 with K[NO⌢a-b] (NO⌢- = 2-picolinate, a or 2-quinaldinate, b) gave neutral [(p  -cymene)RuCl(NO⌢a-b)] (1a–b), complexes which were treated with pyridine-based meridional triamine ligands (′NNN⌢⌢′) to create complexes of the type [RuCl(NO⌢a-b)(′NNN⌢⌢′)] (2a: ′N = Nd  , NO⌢a- = 2-picolinato; 2b: ′N = Nd  , NO⌢b- = 2-quinaldinato; 3a: ′N = Nb  , NO⌢a- = 2-picolinato; 3b: ′N = Nb  , NO⌢b- = 2-quinaldinato; 4a: ′N = Np  , NO⌢a- = 2-picolinato; 4b: ′N = Np  , NO⌢b- = 2-quinaldinato). The new compounds were characterized by elemental analysis, IR and NMR spectroscopy and, 1b was studied by single crystal X-ray diffraction. The complexes 1–4 have been employed as catalysts for the transfer hydrogenation (TH) of acetophenone derivatives to secondary alcohols in the presence of KOH using 2-propanol as a hydrogen source at 82 °C. The highest catalytic activity was obtained with 3a.

Graphical abstractA series of Ru(II) complexes have been synthesized and employed as catalysts for the transfer hydrogenation of ketones.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► [(p  -cymene)RuCl(NO⌢)] and [RuCl(NO⌢)(′NNN⌢⌢′)] complexes were synthesized. ► The new compounds were characterized by elemental analysis, IR and NMR spectroscopy and, 1b was studied by single crystal X-ray diffraction. ► The complexes have been employed as catalysts for the transfer hydrogenation of simple ketones.