Hydrogenation of cyclohexene catalyzed by ruthenium nitrosyl complexes: Crystal structures of catalyst precursors [Cp∗Ru(μ2-NO)2RuCp∗] and [Cp∗Ru(NO)(η2-C6H10)] (Cp∗ = η5-C5(CH3)5)

Hydrogenation of cyclohexene with 0.1 mol% of the (nitrosyl)ruthenium catalyst [Cp∗Ru(NO)(C6H5)2] (1; Cp∗ = η5-C5(CH3)5) under 1.0 MPa of H2 in water at 90 °C for 13 h afforded cyclohexane in 94% yield. The nitrosyl-bridged dinuclear complex [Cp∗Ru(μ2-NO)2RuCp∗] (2) and the mononuclear cyclohexene complex [Cp∗Ru(NO)(η2-C6H10)] (3), which also serve as catalyst precursors, have been obtained from the reaction mixture. X-ray crystallographic analyses of 2 and 3 have revealed that the bridging nitrosyl ligands in 2 form an almost planar Ru2N2 four-membered ring with the Ru–Ru distance of 2.5366(5) Å, whereas the nitrosyl ligand in 3 is linear. On the other hand, a ruthenium complex without a nitrosyl ligand [Cp∗Ru(CH3CN)3][OSO2CF3] proved to be less effective for this hydrogenation.

We have demonstrated that the (nitrosyl)ruthenium complex [Cp∗Ru(NO)(C6H5)2] (1) serves as a catalyst precursor for hydrogenation of cyclohexene. Two nitrosyl complexes 2 and 3 have been obtained from the reaction mixture. The detailed structures of 2 and 3 have been determined by X-ray crystallography.Figure optionsDownload as PowerPoint slide