Component Catalyst Systems

The C12H18 ligand is formed from trimerization of butadiene and is composed of two allyl functions and one olefin moiety. These functionalities coordinate to 

The cationic complex, [Ni(Ci2Hi9)]SbF6 can be made independently from Ni(cyclo-l,5-octadiene)2, butadiene, and HSbFg. This material exhibited similarly high activity toward norbornene polymerization. 

Ultimately it was discovered that introduction of butadiene into the catalyst system was not necessary. Simply adding an equimolar mixture of HSbFg to Ni(O2CR)2 in 1,2-dichloroethane solution of norbornene-type monomers followed by introduction of BFj ff.O and AlEt-3 (1 9 10 Ni B Al molar ratio) produced an 

It was also found that the multi-component catalyst system performed essentially identically to naked nickel in terms of molecular weight control upon addition of the chain transfer agent 1-decene (see Fig. 4.23 and compare to Fig. 4.12). 

Moreover, the microstructure of the norbornene homopolymer that is formed using this multi-component catalyst is identical to that produced by naked nickel as evidenced by and NMR spectroscopy. Based on these observations, it is clear that the active catalyst formed in situ from the multi-component system is very similar to the naked nickel single component catalyst [50]. 

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The rearrangement reaction of 1 requires a two component catalyst system consisting of a Lewis acid and a soluble source of iodide anion. The process concept had a number of requirements for the catalysts in order to achieve commercially useful operation. These were ... 

Multi-component catalyst systems based on palladium compounds and phosphorus compounds show a particularly high activity (35). The high catalytic activity is not deteriorated in the course of polymerization. Substituted norbornene derivates can be used that are otherwise difficult to polymerize. 

Isoalkanes can also be synthesized by using two-component catalyst systems composed of a Fischer-Tropsch catalyst and an acidic catalyst. Ruthenium-exchanged alkali zeolites288 289 and a hybrid catalyst290 (a mixture of RuNaY zeolite and sulfated zirconia) allow enhanced isoalkane production. On the latter catalyst 91% isobutane in the C4 fraction and 83% isopentane in the C5 fraction were produced. The shift of selectivity toward the formation of isoalkanes is attributed to the secondary, acid-catalyzed transformations on the acidic catalyst component of primary olefinic (Fischer-Tropsch) products. 

Trost, B. M. McEachem, E. J. Toste, F. D. A two-component catalyst system for asymmetric allylic alkylations with alcohol pronucleophiles./. Am. Chem. Soc. 1998, 120, 12702-12703. 

BR with narrow MMDs (Mw/Mn > 3.5) and a low solution viscosity can also be obtained by the use of a multi-component catalyst system which comprises the following six components (1) Nd-salt, (2) additive for the improvement of Nd-solubility, (3) aluminum-based halide donor, (4) alumoxane, (5) aluminum (hydrido) alkyl, and (6) diene. The solubility of the Nd-salt is improved by acetylacetone, tetrahydrofuran, pyridine, N,N-dimethylformamide, thiophene, diphenylether, triethylamine, organo-phosphoric compounds and mono- or bivalent alcohols (component 2). The catalyst components are prereacted for at least 30 seconds at 20 - 80 °C. Catalyst aging is preferably performed in the presence of a small amount of diene [397,398 ]. As the additives employed for the increase of the solubility of Nd salts exhibit electron-donating properties it can be equally well speculated that poisoning of selective catalyst sites favors the formation of polymers with a low PDI. 

A two-component catalyst system consisting of two different transition metal complexes (Rh-Pd) has been applied to the enantioselective allylation of diethyl 1-cyanoethylphosphonate. The reaction proceeds with high enantioselectivity to give optically active phosphonic acid derivatives (Scheme 6.11). ° ... 

Sawamura, M., Sudoh, M., and Ito, Y., An enantioselective two-component catalyst system. Rh-Pd-catalyzed allylic alkylation of activated nitriles, 7. Am. Chem. Soc., 118, 3309, 1996. 

Oxides of a variety of metals on finely divided inert support materials initiate polymerization of ethylene and other vinyl monomers by a mechanism that is assumed to be similar to that of heterogeneous Ziegler-Natta polymerization that is, initiation probably occurs at active sites on the catalyst surface [2j. Unlike the traditional Ziegler-Natta two-component catalyst systems, the supported metal-oxide catalysts are essentially one-component systems. Among the metals that have been investigated for these catalyst... 

A two component catalyst system has provided promising results in the alkylation of a 7t-allyl moiety with a prochiral nucleophile (Scheme 44). 

Care must be taken with this reaction, and an alternative procedure is to use a two-component catalyst system by reacting the lactam with a base to produce an activated monomer. This then reacts with a promoter such as the acyl lactam, which initiates the ring-opening growth of the linear polymCT. For a series of cychc lactams, the reaction rates are a function of ring size and are in the order of 8- > 7- > 11- 5- or 6-membered rings. These are important commercial processes, and nylon-4 is also prepared vising this type of reactioiL... 

Processes 4 and 5 in Figure 2.13 are more recent developments entailing dimerization of acrylonitrile. Although formally analogous to the Monsanto process they are quite different because they proceed via catalysis rather than electrolysis. One of these processes developed by Halcon [176] involves liquid-phase reaction of acrylonitrile at 30°C under a nitrogen pressure of 0.7 MPa in the presence of a two-component catalyst system. 

To avoid costly purification of isotactic polypropylene, three-component catalyst systems were developed. Some of the original ones appear to have been reported by Natta himself, who found that addition of Lewis bases enhances the quantity of the crystalline material. Table 5.4 shows the effects of addition of Lewis bases on the amount of crystallinity, reported by Natta. ... 

Thus, from 1976 onwards, the use of multi-component catalyst systems gradually lost its prominence, and the field of olefin meta-... 

On the other hand, two-component catalyst systems, mainly WOCI4 and WCle in combination with a suitable cocatalyst, have been widely employed on a laboratory scale. These were the first catalysts developed for the metathesis of unsaturated fatty acid esters. Although they are more sensitive to moisture and air, they are cheaper and easier to handle than the alkylidene complexes. In this sense, the use of W(OAr)2Cl4 has... 

A three-component catalyst system has been developed for a one-step synthesis of enantioenriched a-aceto g hosphonates (555) from aldehydes (553) and acetyl phosphonate (554). The combination of tridentate Shiff base aluminum complex (556), DBU, and 1/f-benzotriazole provided products (555) in high yields but with moderate enantiomeric ratios (up to 78 22) (Scheme 160). ... 

Direction of addition. A mixture of methyldichlorosilane, acrylonitrile, and a 3-component catalyst system consisting of cuprous chloride, tri-n-butylamine, and N,N,N, N -tetramethylethylenediamine refluxed 40 hrs. while the temp, rises from 51 to over 126° j -cyanoethylmethyldichlorosilane. Y 79%.—The above catalyst system favors the formation of y -adducts. F. e. s. B. A. Bluestein, Am. Soc. 83, 1000 (1961). 

Sawamura M, Sudoh M, Ito Y (1996) An enantioselective two-component catalyst system Rh-Pd-catalyzed allyhc alkylation of activated nitriles. J Am Chem Soc 118 3309-3310... 

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