A general route for the synthesis of hydrido-carboxylate complexes of the type MH(CO)(κ3-OCOR)(PPh3)2 [M = Ru, Os; R = CH3, CH2Cl, C6H5, CH(CH3)2] and their use as precatalysts for hydrogenation and hydroformylation reactions

The synthesis and solid-state IR, 1H and 31P{1H} NMR spectroscopic characterization of complexes of the type MH(CO)(κ3-OCOR)(PPh3)2 [M = Ru, Os; R = CH3, CH2Cl, C6H5 and CH(CH3)2] are reported in this paper. These compounds were obtained by reaction of the respective cationic complex [MH(CO)(NCMe)2(PPh3)2]BF4 with the sodium salt of the corresponding carboxylic acid in a 1:1 v/v dichloromethane/methanol solution at room temperature. The spectroscopic data of these complexes and some DFT calculations reveal an octahedral geometry with a bidentated carboxylate, two equivalent triphenylphosphines in a mutually trans positions, a linear hydride and a linear carbonyl both in the cis-positions of the coordination sphere. The catalytic results indicate that these complexes are efficient and regioselective precatalysts for the quinoline hydrogenation and for the hydroformylation of 1-hexene, under mild reaction conditions (130 °C and 4 atm H2 and 120 °C and 15 atm H2/CO, respectively). For benzothiophene hydrogenation, the osmium complexes showed low activities whereas the analogous ruthenium complexes were catalytically inactive under somewhat more drastic reaction conditions to those of the quinoline hydrogenation (140 °C and 10 atm H2).

Complexes MH(CO)(κ3-OCOR)(PPh3)2 were obtained by reaction of the respective cationic complex [MH(CO)(NCMe)2(PPh3)2]BF4 with the sodium salt of the corresponding carboxylic acid in a CH2Cl2/MeOH solution at room temperature. These complexes showed to be efficient precatalysts for the quinoline hydrogenation and for the hydroformylation of 1-hexene. The osmium complexes showed low activities for the benzothiophene hydrogenation whereas the corresponding ruthenium ones were inactive.Figure optionsDownload as PowerPoint slide