Synthesis, characterization and some catalytic properties of ruthenium complexes Ru(PPh3)2Cl2(L)2 [L = 4-But-py, 4-vinyl-py, 4-CN-py, 4-Me-py, 3-Me-py, L2 = 4,4′-bipy]. Kinetics of cyclohexene hydrogenation catalysed by Ru(PPh3)2Cl2(4-But-py)2

Article abstract of DOI:10.1016/0277-5387(95)00318-4

The complexes Ru(PPh₃)₂Cl₂(L)₂ (L = 4-Bu^t-py, 4-vinyl-py, 4-CN-py, 4-Me-py, 3-Me-py, L₂ = 4,4′-bipy) have been prepared by reaction of RuCl₂(PPh₃)₃ with the appropriate ligand under mild conditions and characterized by elemental analysis, IR, NMR (¹H and ³¹P) and UV vis spectra : the Ru^II derivatives display a RuP₂Cl₂N₂ core with a trans, cis, cis arrangement of the donor atoms. Ru(PPh₃)₂Cl₂(4-Bu^t-py)₂ is an efficient catalyst precursor for the homogeneous hydrogenation of cyclohexene and benzaldehyde under moderate conditions. A kinetic study of the hydrogenation of cyclohexene led to a rate law r = k_cat[Ru][H₂2], which corresponds to a mechanism involving a fast coordination of cyclohexene to an electronically unsaturated hydride RuHCl(PPh₃)₂(4-Bu^t-py), followed by a rate-limiting oxidative addition of H₂ and rapid reductive elimination of the product.