Abstract
Pyridyl-thiourea complexes of formula [(Cym)MCl(κ(2)N(py),S-H(2)NNS)][SbF(6)] (Cym = η(6)-p-MeC(6)H(4)iPr; H(2)NNS = N-(p-tolyl)-N'-(2-pyridylmethyl)thiourea); M = Ru (1), Os (2)) were synthesized by reacting the corresponding metal dimers [{(Cym)MCl}(2)(μ-Cl)(2)] with H(2)NNS in the presence of NaSbF(6). Subsequent chloride abstraction with AgSbF(6), followed by NH deprotonation using NaHCO(3), afforded the cationic complexes [(Cym)M(κ(3)N(py),N(amide),S-HNNS)][SbF(6)] (M = Ru (5a), (5c); M = Os (6a, 6c)) and [(Cym)M(κ(2)N(amide),S-HNNS)][SbF(6)] (M = Ru (5b); M = Os (6b)). The proposed structures for the prepared compounds are based on NMR data. Complexes 5a, 5b, and 6a, 6b evolve to the thermodynamically more stable species 5c and 6c, respectively, in which the deprotonated ligand HNNS adopts a κ(3)N(py),N(amide),S coordination mode. Complexes 5c and 6c activate H(2), behaving as frustrated Lewis pair (FLP) species, and catalyze (5c and/or 6c) the hydrogenation of polar multiple bonds, including the C=N bonds of N-benzylideneaniline and quinoline, the C=C bond of methyl acrylate, and the C=O bond of 2,2,2-trifluoroacetophenone.