Polymerization nickel catalysts

Anionic N,0 ligands have been particularly successful in the search for new oligomerization/polymerization nickel catalysts. Pioneering work by Gavell showed that nickel aryls containing pyridinecarboxylate ligands 170 and 171 are... 

The effect of physical processes on reactor performance is more complex than for two-phase systems because both gas-liquid and liquid-solid interphase transport effects may be coupled with the intrinsic rate. The most common types of three-phase reactors are the slurry and trickle-bed reactors. These have found wide applications in the petroleum industry. A slurry reactor is a multi-phase flow reactor in which the reactant gas is bubbled through a solution containing solid catalyst particles. The reactor may operate continuously as a steady flow system with respect to both gas and liquid phases. Alternatively, a fixed charge of liquid is initially added to the stirred vessel, and the gas is continuously added such that the reactor is batch with respect to the liquid phase. This method is used in some hydrogenation reactions such as hydrogenation of oils in a slurry of nickel catalyst particles. Figure 4-15 shows a slurry-type reactor used for polymerization of ethylene in a sluiTy of solid catalyst particles in a solvent of cyclohexane. 

The first example of homogeneous transition metal catalysis in an ionic liquid was the platinum-catalyzed hydroformylation of ethene in tetraethylammonium trichlorostannate (mp. 78 °C), described by Parshall in 1972 (Scheme 5.2-1, a)) [1]. In 1987, Knifton reported the ruthenium- and cobalt-catalyzed hydroformylation of internal and terminal alkenes in molten [Bu4P]Br, a salt that falls under the now accepted definition for an ionic liquid (see Scheme 5.2-1, b)) [2]. The first applications of room-temperature ionic liquids in homogeneous transition metal catalysis were described in 1990 by Chauvin et al. and by Wilkes et ak. Wilkes et al. used weekly acidic chloroaluminate melts and studied ethylene polymerization in them with Ziegler-Natta catalysts (Scheme 5.2-1, c)) [3]. Chauvin s group dissolved nickel catalysts in weakly acidic chloroaluminate melts and investigated the resulting ionic catalyst solutions for the dimerization of propene (Scheme 5.2-1, d)) [4]. 

Figure 7.4-1 Nickel catalysts used for the polymerization and oligomerization of ethylene in...

Many recent publications have described the stereospecific polymerization of dienes by ir-allyl compounds derived from Cr, Nb, Ni, etc. Of particular interest is the work of Durand, Dawans, Teyssie who have shown that ir-allyl nickel catalysts (XXI) in the presence of certain additives polymerize butadiene stereospecifically (87, 38). The active center results from reaction of acidic additives with the transition metal. 

The nickel catalyst under the condition for the 1 1 codimerization is not known to dimerize or polymerize ethylene, although a similar catalyst system has been known to dimerize propylene (26, 27) via a w-allyl intermediate. 

Nickel 2,6,10-dodecatrien -1,12-diyl, as catalyst for butadiene polymerization, 23 303 Nickel formate as nickel catalyst, 32 226-229 Nickel hydride... 

The transition group compound (catalyst) and the metal alkyl compound (activator) form an organometallic complex through alkylation of the transition metal by the activator which is the active center of polymerization (Cat). With these catalysts not only can ethylene be polymerized but also a-olefins (propylene, 1-butylene, styrene) and dienes. In these cases the polymerization can be regio- and stereoselective so that tactic polymers are obtained. The possibilities of combination between catalyst and activator are limited because the catalytic systems are specific to a certain substrate. This means that a given combination is mostly useful only for a certain monomer. Thus conjugated dienes can be polymerized by catalyst systems containing cobalt or nickel, whereas those systems... 

By taking advantage of the simultaneous enzyme inhibition by nickel, the nickel-catalyzed ATRP, and the stereoselectivity of the enzyme, Peters et al. obtained chiral block copolymers by this method from 4-methyl-e-caprolactone (4-MeCL) by [27], The polymerization of racemic 4-MeCL showed good enantioselectivity and produced a chiral macroinitiator with ATRP endgroup by selectively polymerizing only the (5 )-4-MeCL. Macroinitiation was then started by adding the nickel catalyst and methyl methacrylate (MMA) to the reaction mixture, which simultaneously inhibited the enzyme and activated the ATRP process. Chiral poly[MMA-fe-(5 )-4-MeCL] was successfully obtained in this synthesis. 

Transition metal-catalyzed polymerizations have been reported to give high-purity, regioregular poly-3-alkylthio-phenes suitable for use in electronic devices. Thus, the Negishi protocol using a nickel catalyst and Rieke zinc was employed for the polymerization of 63 to produce the product as a low molecular weight polymer <2003CC2548>. 

Good evidence has been obtained that heterogeneous iron, ruthenium, cobalt, and nickel catalysts which convert synthesis gas to methane or higher alkanes (Fischer-Tropsch process) effect the initial dissociation of CO to a catalyst-bound carbide (8-13). The carbide is subsequently reduced by H2to a catalyst-bound methylidene, which under reaction conditions is either polymerized or further hydrogenated 13). This is essentially identical to the hydrocarbon synthesis mechanism advanced by Fischer and Tropsch in 1926 14). For these reactions, formyl intermediates seem all but excluded. 

Kanbara has since generated a family of poly(iminoarene)s by reaction of 1,3-dibromo-benzene, 4,4-dibromodiphenyl ether, 2,6- and 3,5-dibromopyridines, 2,4-dibromothiophene, and l,l -dibromoferrocene with a variety of bifunctional arylamines [229]. In many cases, no polymer was obtained, but for polymerizations involving dibromobenzene and 2,6-dibromopyridine, materials with JVfn values of over 10,000 were obtained. Spectral data were provided for poly(2,6-aminopyridine) and a polymer made from dibromobenzene and a dia-rylamino sulfone. These authors have also investigated nickel catalysts for the polymerization of diamines with dichloroarenes, but the materials generated had molecular weights below 10,000 in most cases [230]. 

Subsequent hydrogenation (Scheme 5) using a nickel catalyst affords the saturated ditetrahydrofurfuryl propane (19) (59). Ditetrahydrofurfuryl propane (60) is a solvent and co-catalyst for the selective polymerization of dienes to 1,2-poly dienes. 

Discussion Point DPP. Eigures 13 and 14 represent reaction schemes for the polymerization of ethylene and of propylene by diimine-nickel catalysts. Erom these schemes predict how the rates ofpolyethylene and ofpolypropylene formation should depend on the concentrations of the respective monomers. What infiiience should the kind of anion present be expected to have on the rates ofpolymer formation in each of these cases How would these answers differ from those to the same questions with regard to zirconocene-based polymerization catalysts ( Eigure IT) ... 

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