Synthesis and Catalytic Activity of Ruthenium(II) Complexes Containing Pyridine-Based Tridentate Triamines (′Nnn′) and Pyridine Carboxylate Ligands (NO)

Abstract

The reaction of [(p-cymene)RuCl<inf>2</inf>]<inf>2</inf> with K[NO <inf>a-b</inf>] (NO- = 2-picolinate, a or 2-quinaldinate, b) gave neutral [(p-cymene)RuCl(NO<inf>a-b</inf>)] (1a-b), complexes which were treated with pyridine-based meridional triamine ligands (′NNN ′) to create complexes of the type [RuCl(NO<inf>a-b</inf>) (′NNN′)] (2a: ′N = N<inf>d</inf>, NOa- = 2-picolinato; 2b: ′N = N<inf>d</inf>, NOb- = 2-quinaldinato; 3a: ′N = N<inf>b</inf>, NOa- = 2-picolinato; 3b: ′N = N<inf>b</inf>, NOb- = 2-quinaldinato; 4a: ′N = N<inf>p</inf>, NOa- = 2-picolinato; 4b: ′N = N<inf>p</inf>, NOb- = 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. © 2012 Elsevier B.V. All rights reserved.