Transfer Hydrogenation of Aryl Ketones with Half-Sandwich RuII Complexes That Contain Chelating Diamines

Abstract

In a comparative study, half-sandwich complexes of RuII (1) with pyridine-based chelating diamine [NN = 2-aminomethylpiperidine (ampi), a; 2-aminomethylpyridine (ampy), b; 8-aminoquaniline (aquan), c; 4,4'-dimethyl-2,2'-bipyridine (dbipy), d; 2,2'-bipyridine (bipy), e] or amine amide (Ts-ampi, 2a) were synthesized by cleavage of [{(?6-p-cymene)Ru(mu-Cl)Cl}2] dimer and the resulting complexes were screened for their efficiency in the transfer hydrogenation (TH) of acetophenone in 2-propanol (IPA) at 82 degrees C or in water in HCOONa. Among the complexes, cationic 1a, neutral 2a, and 1b, which bear ampi and ampy, were the most effective in terms of catalyst performance (turnover frequency values: 198, 6000, 23 h1, respectively).