Hydrogenation of arenes under mild conditions using rhodium pyridylphosphine and bipyridyl complexes tethered to a silica-supported palladium heterogeneous catalyst
The rhodium complexes [Rh(COD)(1)]BF{sub 4} (RH(N-P)) and [Rh(COD)(2)]BF{sub 4} (Rh(N-N)), containing the new pyridylphosphine and bipyridyl ligands (1 and 2) with alkoxysilane groups, were tethered on the silica-supported palladium heterogeneous catalyst Pd-SiO{sub 2} to give the TCSM (tethered complex on supported metal) catalysts Rh(N-P)/Pd-SiO{sub 2} and Rh(N-N)/Pd-SiO{sub 2}. Under the mild conditions of 70 C and 4 atm of H{sub 2}, the two TCSM catalysts are very active for the hydrogenation of arenes (PhCO{sub 2}Me, PhOH, toluene, PhOCH{sub 3}, PhCO{sub 2}Et, 4-CH{sub 3}C{sub 6}H{sub 4}CO{sub 2}Et, dimethyl terephthalate) to cyclohexanes; the activities are higher than those of the separate homogeneous Rh(N-P) and Rh(N-N) complex catalysts, the silica-supported palladium catalyst Pd-SiO{sub 2}, or the rhodium complex catalysts tethered on just SiO{sub 2}. The catalysts are easily separated from the reaction mixtures and can be recycled several times without losing activity. Of the two TCSM catalysts, the higher activity for the hydrogenation of anisole to methyl cyclohexyl ether was observed for Rh(N-N)/Pd-SiO{sub 2}, which gives a TOF value of 3060 mol of substrate converted/((mol of Rh)h) and a TO value of 14500 mol of substrate converted/(mol of Rh) in 6 h. Reactions of acetophenone lead to hydrogenation of the arene ring, the carbonyl group, or both, depending on the catalyst (Rh(N-P)/Pd-SiO{sub 2} or Rh(N-N)/Pd-SiO{sub 2}) and the solvent (heptane or ethanol).
- Research Organization:
- Iowa State Univ., Ames, IA (US)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 20017494
- Journal Information:
- Organometallics, Vol. 19, Issue 4; Other Information: PBD: 21 Feb 2000; ISSN 0276-7333
- Country of Publication:
- United States
- Language:
- English
Similar Records
Studies of Immobilized Homogeneous Metal Catalysts on Silica Supports
Hydroformylation of 1-octene under atmospheric pressure catalyzed by rhodium carbonyl thiolate complexes tethered to silica