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• 52090-23-0 3-(diphenylphosphanyl)propyltriethoxysilane 

Relevant academic research and scientific papers

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

Novel catalysts consisting of a tethered complex on a supported metal (TCSM) are described. 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 produce the tethered complex catalysts Rh-P/Pd-SiO2, Rh-P/Ni-SiO2, and Rh-P/Au-SiO2. The structure of the tethered Rh-P complex in all of these combination catalysts was similar to that of the free Rh-P complex. These TCSM catalysts were used to catalyze the hydrogenation of arenes at 40°C and 1 atm of H2. Rh-P/Pd-SiO2 was the most active TCSM catalyst and gave a maximum turnover frequency (TOF, mole H2/mole Rh min) of 2.9 and a turnover (TO, mole H2/mole Rh) of 1940 during a 23 hr period in the hydrogenation of toluene. The phosphine ligand was oxidized to the phosphine oxide when the tethered Rh-P complex catalyst stood in air for ≥ 2 mo. This air-aged Rh-P/Pd-SiO2 was more active than the fresh catalyst for the hydrogenation of toluene, but the air-aged Rh-P/SiO2 became inactive for this reaction. These two air-aged catalysts were characterized by solid state 31P NMR and DRIFTS using CO as a probe.

Immobilized rhodium hydrogenation catalysts

The showcase catalyst for olefin hydrogenations is Wilkinson's complex ClRh(PPh3)3 (1). Here, the Wilkinson-type catalyst ClRh[Ph2P(CH2)3Si(OEt)3]3 (2), trans-ClRh(CO)[Ph2P(CH2)3Si(OEt) 3]2 (3), and the chelate complex ClRh(PPh3)[Ph2PCH2CHOHCH2PPh 2] (4) have been synthesized using the bifunctional ligands Ph2P(CH2)3Si(OEt)3 (5) and Ph2PCH2CHOHCH2PPh2 (6), and fully characterized. The dihydride complex 4(H)2 has been generated in situ and characterized with NMR. Complexes 2, 3, and 4 have been immobilized on silica, giving 2i, 3i, and 4i, respectively, which have been studied by solid-state NMR. The catalytic activities of 2i-4i for the hydrogenation of 1-dodecene (7), 2-cyclohexen-1-one (8), and 4-bromostyrene (9) are compared with those of the homogeneous analogs 2 and 3, as well as with 1. While there are no substantial differences between 1 and 2 concerning TON and TOF, 2i shows reversed activity for the three test samples: dodecene gives the lowest TOF, followed by bromostyrene and cyclohexenone. However, TON and maximal yield are the same for 1, 2, and 2i. In contrast to 1 and 2, the immobilized catalyst 2i can be recycled seven times, 4i three times. Catalysts 3 and 3i give maximal TOF for the hydrogenation of 7, followed by 8 and 9. The yields are below 100% for the homogeneous catalyst 3, but immobilization (3i) gives maximum yields for all substrates.