The coordination chemistry of carbon dioxide and its relevance for catalysis: a critical survey

https://www.chem.ccu.edu.tw/~joyce/referance/gump/Rh/TCSM/Organometallics%201999,%2018,%20989.pdf

Combined Homogeneous and Heterogeneous Catalysts. Rhodium and Platinum Isocyanide Complexes Tethered on Silica-Supported Metal Heterogeneous Catalysts: Arene and Cyclohexanone Hydrogenation †

The rhodium carbonyl thiolate complex, Rh2[μ-S(CH2)3Si(OCH3)3]2(CO)4 (Rh–S) was tethered to phosphine-modified Pd–SiO2 (P–(Pd–SiO2)), which was prepared by tethering the phosphine ligand Ph2P(CH2)3Si(OC2H5)3 to Pd–SiO2, to give the tethered complex catalyst Rh–S/P–(Pd–SiO2). Also, the phosphine-substituted Rh2[μ-S(CH2)3Si(OCH3)3]2[Ph2P(CH2)3Si(OC2H5)3]2(CO)2 (Rh–S–P) was tethered to several silica-supported metal heterogeneous catalysts M–SiO2 (M=Pd, Pt, Ru, Ir) to give Rh–S–P/M–SiO2. These complex catalysts, consisting of a tethered complex on a supported-metal (TCSM), were used to catalyze the hydroformylation of olefins and the hydrogenation of toluene under atmospheric pressure. In the presence of phosphorus donor-ligands, all the TCSM catalysts are active for the hydroformylation of olefins under the mild conditions of 60°C and 1 atm of H2 and CO (1:1). The most active catalysts, Rh–S/P–(Pd–SiO2) and Rh–S–P/Pd–SiO2, give maximum TOF values of 1.04 and 0.88 (mol aldehyde/mol Rh min), respectively, and TO values of 905 and 703 (mol aldehyde/mol Rh) during 22.5 h and 23.5 h in the hydroformylation of 1-octene. The Rh–S–P/Pd–SiO2∼PPh3 catalyst system maintains its activity through three cycles and 68 h to give a total turnover of 2118 mol aldehyde/mol Rh. These activities are higher than those of the homogeneous rhodium thiolate complex catalyst (Rh–S–P) and the rhodium thiolate complex catalysts tethered on just SiO2(Rh–S/P–SiO2 and Rh–S–P/SiO2). The effects of the phosphorus ligand and PR3/Rh mole ratio on the hydroformylation rates, conversions, and chemo- and regioselectivities for aldehyde were also investigated. The Rh–S/P–(Pd–SiO2) and Rh–S–P/Pd–SiO2 catalysts are also active for the hydrogenation of toluene under the mild conditions of 40°C and 1 atm of H2; they are much more active than the homogeneous rhodium thiolate complex catalyst Rh–S–P, the simple silica-supported heterogeneous palladium catalyst (Pd–SiO2) and the rhodium thiolate complex catalysts tethered on just SiO2(Rh–S/P–SiO2 and Rh–S–P/SiO2). The synergistic advantages of the two components (tethered complex and supported metal) of the TCSM catalysts are greater for the hydrogenation of toluene than for the hydroformylation of 1-octene.

Combined homogeneous and heterogeneous catalysts.: Rhodium carbonyl thiolate complexes tethered on silica-supported metal heterogeneous catalysts: olefin hydroformylation and arene hydrogenation

The rhodium–phosphine complex, RhCl(CO)[Ph2P(CH2)3Si(OC2H5)3]2 (Rh–P), was tethered to silica-supported metal heterogeneous catalysts, Pd–SiO2, Ni–SiO2 and Au–SiO2, to give the tethered complex catalysts Rh–P/Pd–SiO2, Rh–P/Ni–SiO2 and Rh–P/Au–SiO2. An IR (DRIFTS) study shows that the structure of the tethered rhodium–phosphine complex (Rh–P) in all of these combination catalysts is the same as that of the free Rh–P complex. These heterogenized complex catalysts consisting of a tethered complex on a supported metal (TCSM) were used to catalyze the hydrogenation of arenes under the mild conditions of 40°C and 1 atm of H2. The most active TCSM catalyst Rh–P/Pd–SiO2 is not only much more active than the homogeneous Rh–P complex and Pd–SiO2 but also much more active than the rhodium–phosphine complex tethered on just SiO2 (Rh–P/SiO2). The Rh–P/Pd–SiO2 catalyst gives a maximum turnover frequency (TOF, mol H2/mol Rh min) of 2.9 and a turnover (TO, mol H2/mol Rh) of 1940 during a 23 h period in the hydrogenation of toluene. When the tethered rhodium–phosphine complex catalyst stands in air for 2 months or longer, the phosphine ligand is oxidized to the phosphine oxide. This air-aged Rh–P/Pd–SiO2 is much more active than the fresh catalyst for the hydrogenation of toluene, but the air-aged Rh–P/SiO2 becomes inactive for this reaction. These two air-aged catalysts were characterized by solid state 31 P NMR and DRIFTS using CO as a probe.

Rhodium–phosphine complex catalysts tethered on silica-supported heterogeneous metal catalysts: arene hydrogenation under atmospheric pressure

Rhodium amine complexes, RhCl(CO)2[Et2N(CH2)3Si(OCH3)3] (Rh–NEt2), RhCl(CO)2[H2N(CH2)3Si(OC2H5)3] (Rh–NH2) and RhCl(COD)[H2NCH2CH2NH(CH2)3Si(OCH3)3] (Rh(COD)(N–N)), were tethered to the silica-supported metal heterogeneous catalysts, M–SiO2 (M=Pd, Ni, Au), to give the TCSM (tethered complex on supported metal) catalysts, Rh–NEt2/M–SiO2 (M=Pd, Ni, Au), Rh–NH2/Pd–SiO2 and Rh(COD)(N–N)/Pd–SiO2. These TCSM catalysts exhibit activities, at 40°C and 1 atm of H2 pressure, for the hydrogenation of arenes that are higher than those of the separate homogeneous rhodium amine complexes, the separate silica-supported metal heterogeneous catalysts or the rhodium complex catalysts tethered on just SiO2. The activities of the TCSM catalysts are strongly affected by both the tethered rhodium amine complex and the SiO2-supported metal. Among these TCSM catalysts, Rh–NEt2/Pd–SiO2 exhibits the highest activity for the hydrogenation of toluene; its maximum TOF is 7.2 mol H2 (mol Rh min)-1 while its TO is 1919 mol H2 (mol Rh)-1 during a 5 h period. IR(DRIFT) spectral studies of the TCSM catalysts before and after being used for the hydrogenation of toluene show that during the hydrogenation, the two CO ligands of Rh–NEt2/M–SiO2 (M=Pd, Ni, Au) are lost from the rhodium center. After standing in air for one month, Rh–NEt2/Pd–SiO2 becomes more active for the hydrogenation of toluene, but the activity of the air-aged Rh(COD)(N–N)/Pd–SiO2 is lower than that of the fresh catalyst.

P. Mastrorilli

Papers

Catalytic activity of Pd (AcO)2 coordinated to cross-linked polymeric isocyanides