THE CATALYTIC ACTIVITY OF NEW RUTHENIUM(II) COMPLEXES CONTAINING CHELATING DIPHOSPHINE LIGAND IN THE HOMOGENEOUS HYDROGENATION OF CYCLOHEXENE

Abstract

A series of new hydridocarbonyl ruthenium(II) complexes containing chelating diphosphine ligands of the type [RuHCl(CO)(PPh3)(L-L)] [L-L = Ph2PCH2PPh, 2, Ph2PCH2CH2PPh2 3, Ph2PCH2CH2CH2PPh2 4, cis-Ph2PCH=CHPPh2 5 and Fe(eta5-C5H4PPh2)2 6] has been prepared by the reactions of [RuHCI(CO)(PPh3)3] 1 with Ph2PCH2PPh2 [dppm, bis(diphenylphosphino)methane], Ph2PCH2CH2PPh2 [dppe, 1,2-bis(diphenylphosphino)ethane], Ph2PCH2CH2CH2PPh2 [dppp, 1,3-bis(diphenylphosphino)propanel, cis-Ph2PCH=CHPPh2 [dppv, cis-1,2-bis(diphenylphosphino)ethylene] and Fe(eta5-C5H4PPh2)2 [(dppf, 1, l'-bis(diphenylphosphino)ferrocene] in boiling PhMe. The compounds 2-6 are moderately stable in solution. The new compounds were characterized by elemental analysis, IR and H-1 NMR spectroscopy. Compounds 1-6 have been shown to catalyse the homogeneous hydrogenation of the C=C bond of cyclohexene; some relations between structures and catalytic activities are described. The Arrhenius activation energy of cyclohexene for compound 4 is 33.0 kJ mol-1.