Synthesis and catalytic properties of the complex [OsH(CO)(NCMe)2(PPh3)2]BF4

Article abstract of DOI:10.1016/S0020-1693(96)05434-5

The cationic complex [OsH(CO)(NCMe)₂(PPh₃)₂]⁺ (4), isolated as its BF₄^- salt, was synthesized in high yields by reaction of OsHCl(CO)(PPh₃)₃ (3) with acetonitrile in the presence of NaBF₄. The spectroscopic data are consistent with an octahedral geometry around the osmium atom, with two phosphines mutually trans and the acetonitriles mutually cis. Complex 4 is shown to be an efficient precatalyst for the hydrogenation of benzaldehyde, cyclohexanone, cyclohexene and quinoline. For the hydrogenation of carbonyl compounds to their corresponding alcohols in 2-methoxyethanol, complex 4 showed a catalytic activity somewhat lower than 3 and than their analogous complexes of ruthenium. However, for the hydrogenation of cyclohexene to cyclohexane and for the quinoline reduction to 1,2,3,4-tetrahydroquinoline, in xylene solvent, the activities were higher for the osmium complexes. The results show that the cationic osmium complex is a more efficient precatalyst for the hydrogenation of C=C and C=N bonds than for C=O bonds in selected substrates.