Molecular hydrogen and water activation by transition metal frustrated Lewis pairs containing ruthenium or osmium components: catalytic hydrogenation assays.

The transition metal frustrated Lewis pair compounds [(Cym)M(κS,P,N-HL1)][SbF] (Cym = η--MeCHiPr; H2L1 = -(-tolyl)-'-(2-diphenylphosphanoethyl)thiourea; M = Ru (5), Os (6)) have been prepared from the corresponding dimer [{(Cym)MCl}(μ-Cl)] and H2L1 by successive chloride abstraction with NaSbF and AgSbF and NH deprotonation with NaHCO. Complexes 5 and 6 and the previously reported phosphano-guanidino compounds [(Cym)M(κP,N,N'-HL2)][SbF] [H2L2 = ,'-bis(-tolyl)-''-(2-diphenylphosphanoethyl) guanidine; M = Ru (7), Os (8)] and pyridinyl-guanidino compounds [(Cym)M(κN,N',N''-HL3)][SbF] [H2L3 = ,'-bis(-tolyl)-''-(2-pyridinylmethyl) guanidine; M = Ru (9), Os (10)] heterolytically activate H in a reversible manner affording the hydrido complexes [(Cym)MH(H2L)][SbF] (H2L = H2L1; M = Ru (11), Os (12); H2L = H2L2; M = Ru (13), Os (14); H2L = H2L3; M = Ru (15), Os (16)). DFT calculations carried out on the hydrogenation of complex 7 support an FLP mechanism for the process.