The effects of various loadings of Pd and Au supported on silica to which rhodium complexes of the type Rh(COD)[H2NCH2CH2NH(CH2)3Si(OCH3)3](X) were tethered were investigated at 40°C and 1 atm H2. The influence of the X- anion in the complex on the activities of the tethered complex on supported metal catalysts was also studied. The arene hydrogenation activities of the catalysts were examined. PF6-Rh(N-N)/Au:Pd-SiO2, with the weakly coordinating PF6- anion, was the most active catalyst, and remained highly active for toluene hydrogenation through at least catalytic cycles involving 2900 mole H2/mole Rh turnovers over 19 hr. The catalysts with added Au were less active by a factor of two, but the activity was dependent on the Pd and Rh complex loadings. A mechanism which involved dissociative adsorption of H2 on the supported Pd was proposed. The hydrogen spilled over onto the silica surface where it was used by the Rh complex to hydrogenate the arene substrate.
Angelici,Perera
p. 99 - 111
(2008/10/09)
More Articles about upstream products of 255390-98-8