Other Nickel Catalysts

In a later report, Bazan and coworkers combined living insertion polymerization with living ATRP techniques to synthesize graft copolymers (Schneider et al., 2008). Polymerization of ethylene followed by copolymerization with 5-norbomen-2-yl-2 -bromo-2 -methyl propano-ate using 84c activated with Ni(COD)2 furnished a PE macroinitiator. Subsequent polymerization with MMA by living ATRP methods furnished PE-gra -PMMA copolymers. 

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Hydrogenation of benzene and its homologs over other nickel catalysts requires higher temperatures (170-180°) and/or higher pressures [43,48,391],... 

Other products were dimethyl ether (DME), methane and carbon dioxide. The data in Table I show that high yields of carbonylated products were produced with nickel catalysts supported on activated carbon and carbon black. Other nickel catalysts gave mainly methane and dimethyl ether. It is clear that a carbonaceous carrier is essential for the appearance of carbonylation activity for the nickel catalyst. The role of the carbonaceous carrier will be discussed later. 

Aldehydes are readily hydrogenated to the corresponding alcohols over nickel and copper-chromium oxide catalysts.1 In general, Raney Ni, especially highly active ones such as W-6,2 are preferred to other nickel catalysts for the hydrogenations at low temperatures and pressures. Raney Ni may further be promoted by the addition of triethylamine2 or triethylamine and a small amount of chloroplatinic acid,3 4 as shown in eqs. 5.1 and 5.2. 

Alternative catalysts such as palladium-on-barium sulfate (poisoned by synthetic quinoline) (24), "P-2" nickel boride (with ethylenediamine) (25), and other nickel catalysts (19c) can be used in place of Lindlar catalyst. However, in our hands selective hydrogenation of triple bonds to Z olefins proceeds with the greatest stereoselectivity with Lindlar catalyst. Palladium-on-barium sulfate (in ethanol with quinoline) can give considerable over-reduction and isomerization to the E isomer (22a). Use of "P-2" nickel boride as the catalyst at room temperature usually gives a. 2% of the J5 isomer (e.g. 23). 

Bis(ylide)nickel catalysts are of high chemical variability and show superior performance in the activation of unsaturated substrates such as acetylene. The normalized polymerization activity in dimethyl sulfoxide (DMSO) of 500 mol polymerized acetylene per mol nickel (h aim) by far exceeds that of structurally related phosphane catalysts by a similar order of magnitude as observed in ethylene polymerizations (see Sections 1.2 and 1.3.1). To our knowledge this activity even exceeds that of all other nickel catalysts reported so far (Fig. 1.4). 

The rate controlling step for reaction involves methane adsorption. Catalyst structure has a marked effect on the kinetics of the reaction. Thus, under certain conditions the rate of reaction over a Ni/Kieselguhr catalyst at 911 K is first order with respect to the partial pressure of CH4 and independent of H2O and product partial P, while for other nickel catalysts the rate depends on the partial P of H2O, H2, and CO. ... 

As advantages of Raney metals, in particular of Raney nickel, it is stated that, as with noble-metal catalysts, it is possible to work under mild conditions. One is warned against hydrogenation with Raney nickel at high temperatures because explosive reactions can occur. In general it is possible to work with Raney nickel at temperatures 20-40° below those needed for the other nickel catalysts described on page 24. However, Raney nickel loses its superior activity at 100-150°, so that at higher temperatures the older nickel catalysts can be used with equal success.154... 

The discovery by Sabatier (1) of the reducing power of finely divided nickel, although unsuccessful in the reduction of pyridine to piperidine, led to the investigation of other nickel catalysts (prepared from nickel salts or oxides) for the same purpose. The development of Raney nickel catalyst (2) gave to the chemist a more active form of this metal. Its activity in the hydrogenation of the pyridine ring was first studied by Adkins (3) and his co-workers at the University of Wisconsin. Since this investigation, it has enjoyed wide use in the catalytic reduction of many pyridines. 

Other nickel-catalyst systems were also demonstrated to catalyse amina-tion of phenol derivatives, such as Ni(COD)2/SIPr-catalysed amination of aiyl carbamates, Ni(COD)2/dppf-catalysed amination of aryl sulfamates, and (dppf)Ni(o-tolyl)Cl-catalysed amination of aiyl sulfamates, mesylates, and triflates/ ... 

Other nickel catalyst systems can cyclodimerize butadiene to 2-methylene-vinylcyclopentane (Kiji et a ., 1970a, b) or linearly dimerize it to (E,E)-1,3,6-octatriene in high yield [Eq. (85) (Pittman and Smith, 1975)]. 

The introduction of magnesia to what seems an already complicated mixture is interesting mainly because it was also included in other nickel catalysts such as the raschig-ring catalysts for steam reforming. It is now realized that the molecular dimensions of magnesia are similar to those of cobalt and nickel oxides, and that magnesiirm can replace cobalt and nickel in solid solution within a crystalhne lattice. This can make catalyst reduction easier and result in the formation of smaller, more stable metal crystallites. 

In 1931 Homer Adkins came to the conclusion that Raney nickel was better than any other nickel catalyst then available for organic hydrogenation reactions, as well as being more convenient to use. He described the new catalyst in a 1932 paper,and it was soon being widely used in other laboratories. Adkins was one of the first to study the catalyst extensively for a wider range of hydrogenation reactions. 

Zelinsky, the Russian chemist, woiked with nickel oxide/alumina catalysts for a number of hydrogenation reactions and was probably one of the first to describe co-precipitation of nickel oxide and alumina in 1924. Since then many other nickel catalysts with alumina supports have been co-precipitated and used successfully in the production of synthesis gas, hydrogen, and town gas. 

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