Hydroformylation catalysts polymers

The spacer units in 3.60 are assembled from polyphosphazenes that bear p-bromophc-noxy side groups via a lithiation reaction, and treatment with a diorganochlorophosphine to give 3.62. The chemistry is summarized in reaction sequence (45).107 Polymer 3.62 coordinates to a variety of metallo species,108 including osmium cluster compounds and cobalt carbonyl hydroformylation catalysts. When used as a polymeric hydroformylation catalyst, this latter species proved how stable the polyphosphazene backbone is under the drastic conditions often needed for these types of reactions. The weakest bonds in the molecule proved to be those between the phosphine phosphorus atoms and the aromatic spacer groups. 

Inspired by these developments, Osinski and coworkers employed polyglycerol 1 as the soluble polymer instead of a silica or polystyrene support in order to obtain similarly recyclable, but homogeneous, hydroformylation catalysts [42], In this context the hydroxyl groups in polyglycerol have been... 

Polymer supported anionic clusters of Ru3>4 and Os3 4 as well as RuOs3 have been studied as hydroformylation catalysts.(75) The supported clusters were more active than solution analogs, and the mixed metal clusters were the most active. 

Some catalytic properties of silica-appended —PPh2RhX species have been reported. When appended to soluble non-cross-linked polymers, this moiety acts as a hydrogenation catalyst, as does (—PPh2)2Rh(CO)2Cl (—PPh2)Rh(CO)2(acac) and (—PPh2)2RhH(COXPPh3) act as hydroformylation catalysts. Polyphosphite... 

Hydroformylation. A polymer- catalyst for asymmetric hydroform>b propene) to afford branched aldehydes. 

Hydroformylation. A polymer-supported (R,5)-BINAPHOS complex 3 serves as catalyst for asymmetric hydroformylation of gaseous substrates (e.g., 3,3,3-trifluoro-propene) to afford branched aldehydes. 

Fluorous-soluble polymer ligands obtained from copolymerization of p-dipenylphos-phinostyrene and (heptadecylfluoro)decyl acrylate are suitable for the preparation of a Rh-based hydroformylation catalyst. ... 

The thermal instability of rhodium-based hydroformylation catalysts has already been overcome commercially in the Ruhrchemie/Rhone-Poulenc process for propene hydroformylation in which the sodium salt of a sulfonated triphe-nylphosphine ligand (TPPTS, la) is used to solubilize the catalyst in the aqueous phase. In this process, the second phase is toluene and the reaction is carried out as a batch process with rapid stirring to intimately mix the two immiscible phases. After reaction, the system is allowed to separate and the organic phase is simply decanted from the aqueous catalyst phase. Both water-soluble polymers and PAMAM dendrimers have been reported as supports for rhodium-catalyzed hydroformylation under aqueous biphase conditions, but reactivities and regioselec-tivities were only comparable to or worse than those obtained with the reference TPPTS ligand. The aqueous biphase approach has found limited application for the hydroformylation of longer-chain alkenes, because of their very low solubility in water leading to prohibitively slow reaction rates, but there have been a variety of approaches directed at the solution of this problem. 

In a similar fashion close analysis of the hydroformylation catalysts derived from Co2(C0)g and 9 (mw 161.000)(22) revealed an 18Z loss of phosphorous from the polymer and substantial lowering of the molecular weight. 

Yet in spite of these negative aspects, the cobalt catalysts are predominant in industrial applications. The reason is very simple the cost of rhodium. Given its cost, it is imperative that the catalyst be recovered completely. This consideration was partially responsible for the very early and intense interest in hydroformylation with polymer-supported catalysts. 

The covalent anchoring of hydroformylation catalysts onto inorganic silica surfaces was already studied in the late seventies [43]. Chloromethyl silicone polymers were converted to the iodo-analog and subsequently reacted to the diphenylphosphinemethyl polysiloxanes. After treatment with RhCl(CO)(PPh3)2 these materials were used as catalyst in the hydroformylation of 1-hexene (68 bar CO/H2 (1 1), 100 °C, benzene). Under these conditions, however, the metal dissociated from the support. The resulting rhodium carbonyl species was responsible for the activity leading to low selectivities. 

Phosphines. Polymeric phosphines exhibit strong metal-binding properties. Nonpolymeric phosphines, in particular triphenylphosphine, are employed as ligands for cobalt and rhodium in hydroformylation catalysts used in plasticizer manufacture. Extensive efforts have been made to attach phosphine-metal complexes to polymers in order to facilitate catalyst recovery and enhance selectivity... 

The use of soluble polymers as catalysts was also explored by Bayer. His group showed that both diphenylphosphinated polystyrene and diphenylphosphinated poly(ethylene glycol) could be used as recoverable, reusable hydroformylation catalysts. Separation of the catalyst and the reaction products in these cases was achieved by taking advantage of the properties of the polymer chain. Solvent precipitation or membrane filtration both proved to be acceptable techniques to isolate products free from the polymer-bound catalyst. 

Monomeric or polymer-bound C0CI2 is an active acetalization and transac-etalization catalyst [17]. Its efficiency can be improved by the addition of chlorotrimethylsilane [18]. Also, Co2(CO)g or heterogeneous Co catalysts convert olefins in the presence of alcohols into acetals [19, 20]. HCo(CO)4, a typical hydroformylation catalyst and strong acid, is able to reduce under hydroformylation conditions (CO/H2 = 2 l, about 165bar, 160-210°C) acetals of aromatic aldehydes into the corresponding ethers. Interestingly, acetals of aliphatic aldehydes did not react under these conditions. 

Hydroformylation Catalysts Based on Polymer-Bound Transition Metal Complexes... 

M Kant, A. Weigt, S. Bischoff, P. Neumann, U. Schuelke andB. Luecke, Transition metal hydroformylation catalysts based on inorganic-organic polymers, (Institut fuer Angewandte Chemie Berlin-Adlershof eV, Germany). 1997, 96-19612989, 19612989... 

Polyquiaolines have been used as polymer supports for transition-metal cataly2ed reactions. The coordinatkig abiUty of polyqukioline ligands for specific transition metals has allowed thek use as catalysts ki hydroformylation reactions (99) and for the electrochemical oxidation of primary alcohols (100). 

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