Syntheses And Characterizations Of Ru-phosphine-diamine Complexes And Applications In Catalytic Hydrogenations Of Carbonyl Compounds

Fifteen ruthenium triarylphosphine complexes, RuCl₂(MOTPP)₂(L_1-5) (1L_1-5) [MOTPP = tris(4-methoxyphenyl)phosphine; L1 = NH₂CH₂CH₂NH₂;　L2 = NH₂(CH₂)₃NH₂;　L3 = NH₂(CH₂)₄NH₂;　L4 = o-NH₂C₆H₄NH₂; L5 = (S,S)-DPEN], RuCl₂(PPh₃)₂(L_1-5) (2L_1-5), RuCl₂(TFTPP)₂(L_1-5) (3L_1-5) [TFTPP= tris (4-trifluoromethylphenyl) phosphine] were prepared and determined by (31)^P, 1^H-NMR, IR spectra and elemental analyses. And the other two complexes RuCl₂(BDPX)[(S,S)-DPEN] (4L₅) [BDPX=1, 2'-bis(diphenylphosphinomethyl) benzene], RuCl2(BISBI)[(S,S)-DPEN] (5L₅) [BISBI=2, 2'-bis(diphenylphosphino methyl) -1, 1'-biphenyl] were also synthesized. A singlet was observed in the 31P {1^H}-NMR spectra of all the Ru-phosphine-diamine complexes. So it was sure that there was a trans arrangement of the Cl atoms and cis position of phosphine ligands in all the complexes. These complexes were used as catalysts for the hydrogenation of aromatic ketones, and the influences of different phosphines and diamines on the catalytic properties were investigated. The complexes containing diphosphine with large bite angle or triarylphosphine with electron-donating group showed higher catalytic activities. The enantioselectivities of products were almost not influenced by the structures of phosphines. It seemed that the e.e. value was mainly relying on the structures of the substrates and not remarkably influenced by the electron factor or bite angle of ligands. An e.e. of 87% could be obtained by using RuCl₂ (BISBI) [(S, S)-DPEN] (5L₅) as catalyst in the hydrogenation of acetophenone at 5oC. Because of the dissociation and coordination of nine-membered BISBI, there might be two diastereoisomers of RuCl2 (BISBI) [(S, S)-DPEN] (5L5) in solution, and one of them in which the BISBI has matched configuration with S,S-DPEN would show higher catalytic activity and enantioselectivity than another isomer. The structural matched isomer would be stabilized and made the enantioselectivity obviously improved when the reaction temperature decreased. The ruthenium complexes containing triarylphosphine were also used for the chemoselective hydrogenation of a, ?-unsaturated ketone. The electron factor of the phosphine ligands had obviously affects to both the activities and selectivities in the hydrogenation of benzylacetone. For complexes 1L1-3, the conversions and chemoselectivities for the C=O bond decreased as the N-Ru-N chelate ring changed from five-membered to seven-membered. Interestingly, the order was reversed when complexes 2L1-3 was used as catalysts. It may existed a competition between the selectivity for C=C bond and C=O bond in the hydrogenation of benzylacetone. The relatively higher temperature (80oC) was advantageous to the chemoselective hydrogenation for C=O bond.