Phosphine anchored rhodium catalyst

Figure 38. Accumulated surface scans from phosphine anchored rhodium catalyst.

Figure 39. Electron spectrum from phosphine anchored rhodium containing catalyst after 30-min exposure to oxygen plasma etching.

Methylmethacrylate has also been used as a reactant for hydroformy-lations with polymer-anchored rhodium catalysts. Low efficiencies were obtained at high temperatures because of competing polymerization and the branched product predominated. The polymer-supported catalysts gave lower activities and a higher proportion of branched product than the homogeneous analogue at comparable phosphine Rh ratios. 

Hydroformylation of vinyl acetate to give mainly the branched product in >90% ee has been achieved using a rhodium catalyst containing binaphthol and phosphine ligands anchored to polystyrene. 

Schweb and Mecking have reported one of the first examples of noncovalent anchoring of catalysts to soluble polymeric supports in 2001. This noncovalently anchored catalyst featured phosphine ligands that were bound by multiple sulfonate groups to soluble polyelectrolytes using electrostatic interactions. The catalyst system was employed in the hydroformylation of 1-hexene and exhibited typical selectivity for a bis-triphenylphosphine-bound rhodium catalyst. The complex was readily recovered and recycled by ultrafiltration. Independently, Reek et al. described similar systems, but these systems made use of a soluble... 

Hughes, O.R. and Unruh, J.D. (1981) Hydroformylation catalyzed by rhodium complexes with diphosphine ligands. Journal of Molecular Catalysis, 12,71 Sanger, A.R. (1977) Hydroformylation of 1-hexene catalysed by complexes of rhodium(I) with di- or tritertiary phosphines. Journal of Molecular Catalysis, 3,221 Sanger, A.R. and Schallig, L.R. (1977) The structures and hydroformylation catalytic activities of polyphosphine complexes of rhodium(l), and related complexes immobilised on polymer supports. Journal of Molecular Catalysis, 3, 101 Pittman, C.U. and Hirao, A. (1978) Hydroformylation catalyzed by cis-chelated rhodium complexes - extension to polymer-anchored cis-chelated rhodium catalysts. The Journal of Organic Chemistry, 43, 640. 

This is an ion-exchanger like the sulfonated polymer. The siUca surface can also be functionalized with phosphine complexes when combined with rhodium, these give anchored complexes that behave like their soluble and polymer-supported analogues as catalysts for olefin hydrogenation and other reactions ... 

An example of such an analysis of rhodium phosphine ligand anchored catalysts is presented (58). A survey scan of a copolymer containing a diphosphine ligand prior to introduction of the metal is shown in Figure 1, spectrum h. The presence of phosphorus in the polymer is evident from this spectrum. 

A remarkable example of the cooperation of different active sites in a polyfunctional catalyst is the one-step synthesis of 2-ethylhexanol, including a combined hydroformylation, aldol condensation, and hydrogenation process [17]. The catalyst in this case is a carbonyl-phosphine-rhodium complex immobilized on to polystyrene carrying amino groups close to the metal center. Another multistep catalytic process is the cyclooligomerization of butadiene combined with a subsequent hydroformylation or hydrogenation step [24, 25] using a styrene polymer on to which a rhodium-phosphine and a nickel-phosphine complex are anchored (cf Section 3.1.5). 

Here triphenylphosphine, the most important ligand in organometallic catalysis, is coupled to the benzene rings of cross-linked polystyrene. An anchored catalyst is then formed by coordination of the phosphine group to the metal center of a rhodium complex (Eq. 6-2). 

Benes prepared some new chiral phosphines suitable as ligands for this reaction.Capka anchored (C2H50)3Si(CH2)3P(Ph)Men to silica (6). Complexed with rhodium, a catalyst for the enantioselective hydrosilylation of ketones like acetophenone and propiophenone was obtained. 

Hetorogenized Catalysts.—Reaction of [Ru(NH3)60H] + with a Faujasite-type zeolite gives a supported Ru complex, which effects hydroformylation of ethylene the catalytic species may be ruthenium clusters that are trapped in the zeolite cages. The effect of reaction conditions upon the selectivity of the hydroformylation of methyl methacrylate with [RhH(CO)(PPh3)3] or its polymer-anchored analogue has been investigated and hydroformylation of hex-l-ene and cyclo-octa-1,5-diene has been carried out with cobalt, rhodium, and platinum-tin complexes anchored to an ion-exchange resin via quaternary amino-phosphines. ... 

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