Catalyst grafted 235 - rhodium

Barbara, P., Bianchini, C., Dal Santo, V., Meli, A., Moneti, S., Psaro, R., Scaffidi, A., Sordelli, L., and Vizza, F. (2006) Hydrogenation of arenes over silica-supported catalysts that combine a grafted rhodium complex and palladium nanoparticles evidence for substrate activation on Rhsi gle.site-Pdmelal moieties. /. Am, Chem. Soc 128 (21), 7065-7076. 

Figure 3.8. An early example of a hybrid support applied in the rhodium catalysed hydroformylation operated in a continuous flow reactor. Polystyrene containing phosphite ligands were grafted on inorganic silica, such that the catalyst will behave as a homogeneous catalyst when using a compatible solvent...

The rhodium complex with bis(diphenylphosphino)phenoxazine was immobilized on silica using the sol-gel technique or by a direct grafting to commercially available silica [127]. Under standard hydroformylation conditions (CO/H2 atmosphere), a neutral hydridic complex (57) and cationic species (58) (Scheme 4.35) coexist on the support and act as a hydroformylation/hydrogenation sequence catalyst, giving selectively 1-nonanol from 1-octene 98% of 1-octene were converted to mainly linear nonanal which was subsequently hydrogenated to 1-nonanol. The... 

First of all, preliminary experiments were carried out in order to quantify the amount of germanium grafted on the support under our preparation conditions. Results in Table 1 indicated that the amount of Ge grafted on the support never exceeds 4 % of the total amount of Ge introduced. Thus, we can conclude that the main part of introduced germanium reacts on the rhodium metallic surface. This assumption is also confirmed by the decrease of the rhodium surface accessibility measured by H2 chemisorption for some Ge-Rh catalysts whereas the particle size remained constant (samples P80 and Rh80Gel/2, B20 and Rh20Gel/2 or Rh20Ge2). 

A rhodium complex grafted onto MWCNTs was also reported to be very active in cyclohexene hydrogenation [218,242], Such a catalyst is more active than that supported on activated carbon, and interestingly, the turnover frequency (TOF) increases dramatically after recycling. Pd/CNT catalysts were found to be active in cyclooctene [243] and benzene [244] hydrogenation, and for the latter... 

PVP stabilized rhodium or platinum sols (3.5 nm) have been grafted onto mer-capto-derivatized silica. [254] The S-H groups ligate strongly to the metal particles. In this case the grafted catalyts are one to two orders of magnitude more active for the hydrogenation of alkenes than the unsupported colloidal catalysts in the same solvent system, and 300 times more active than commercial Rh/C and Pt/C catalysts. 

Transition metals are widely used as catalysts for nucleophilic substitution reactions and there has been summary of their use in amination reactions. Pd(dba)2-ligand A is reported to be an efficient catalyst for the amination of a variety of aryl chlorides. Poly[(j9-cyclopentadienylmethylstyrene)rhodium] + grafted on to a polymeric sublayer has been used as an effective catalyst for alkoxydefluorination reactions of fluoroarenes. The activity is similar to that of the homogeneous catalyst and may be conserved for repeated applications. 

Thermolysis of the grafted Rh(I) centres gives rise to metallic rhodium particles. Indeed, there is a direct connection with the chemistry of conventionally prepared heterogeneous catalysts. Small 3-dimensional metal particles have been identified after hydrogen reduction of adsorbed rhodium trichloride, but chemisorption of CO causes the formation of Rh (C0)2 centres [69]. This disruption of the metal particles is of clear consequence to the use of such... 

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