Nickel catalysts preparation

The coupling reaction proceeds better when a rigorously degassed Raney nickel catalyst is used, but a nickel catalyst prepared by a much simplifled procedure (Note 9) is also effective. The coupling may also be promoted by other elements, including copper and palladium. 

Various carbon-based catalysts were tested in the investigated air gas-diffusion electrodes pure active carbon [6], active carbon promoted with silver [7] or with both silver and nickel. Catalysts prepared by pyrolysis of active carbon impregnated with a solution of the compound Co-tetramethoxyphenylporphyrine (CoTMPP) are also studied [8],... 

Tillack and co-workers developed a rhodium-catalyzed asymmetric hydrosilylation of butadiyne 258 to afford allenylsilane 260 (Scheme 4.67) [106]. Among more than 30 chiral phosphine ligands investigated, the highest enantioselectivity was observed when the catalyst was prepared from [Rh(COD)Cl]2 (1 mol%) and (S,S)-PPM 259 (2 mol%) to afford the optically active allene 260 with 27% ee. Other metals such as Ir, Pd, Pt or Ni were less effective for example, a nickel catalyst prepared from NiCl2 and (R,R)-DIOP 251 or (S,S)-PPM 259 gave the allene 260 with 7-11% ee. 

Ni(CO)4 is the sole binary carbonyl complex of the elements of group 10 that is stable (Table 8.1). However, very few studies in which Ni(CO)4 is used in the preparation of catalysts have been reported [43]. This is probably due to the difficulty of manipulation of Ni(CO)4 and its very high toxicity. However, surface Ni(CO)4 species have been identified after the interaction of CO with highly dispersed supported nickel catalysts prepared by other routes [44]. Recent interest in the use of Ni(CO)4 has focused on the controlled production of nickel nanoparticles for specific purposes, such as in automotive converters [45]. The use of nickel tetracarbonyl as an agent for the nucleation process in the growth of single-wall carbon nanotubes has also been reported [46]. 

Isolated double bonds in alkenes and cycloalkenes are best reduced by catalytic hydrogenation. Addition of hydrogen is very easy and takes place at room temperature and atmospheric pressure over almost any noble metal catalyst, over Raney nickel, and over nickel catalysts prepared in special ways such as P-1 nickel [13] or complex catalysts, referred to as Nic [49]. 

The reaction of 1-phenylethyl-, 2-octyl-, and 2-butyl-magnesium chloride (36a, b, c) with vinyl bromide (37a), (E)-p-bromostyrene (37b), 2-bromopropene (37c), and bromobenzene (37d) was carried out in the presence of 0.5 mol- % of a nickel catalyst prepared in situ from nickel chloride and the chiral ligand (35). 

The submitters used Raney nickel catalyst prepared as described by Mozingo.2 The checkers used W-6 Raney nickel catalyst. ... 

While hydrosilylation of imines is known to be effected by rhodium catalysts3, nickel catalysts prepared in situ from Ni(0Ac)2 4H20 and thiosemicarbazones are also found to promote the reactions of iV-substituted imines with HSiEt3 in dry DMSO at 35 °C, giving the corresponding secondary amines in excellent yields after basic work-up (equation 77)185. 

Allyl cyanides can be added across alkynes in the presence of a nickel catalyst prepared from (COD)2Ni and (4-CF3CeH4)3P in situ to give functionalized di- or tri-substituted acrylonitriles in a highly stereoselective manner, presumably via n-allylnickel intermediates. a-Siloxyallyl cyanides also react at the y -position of a cyano group with both internal and terminal alkynes to give silyl enol ethers, which can be converted into the corresponding aldehydes or ketones upon hydrolysis.70... 

The compound of formula (5) is next subjected to selective hydrogenation to convert the acetylenic bond to an ethylenic bond. This can be readily accomplished by a number of different catalysts, such as a nickel catalyst prepared from a nickel salt and NaBFi4, Lindlar catalyst, or 5% palladium on barium sulfate in the presence of qunioline. The reaction was run at one atmosphere. Analyses by nuclear magnetic resonance and vapor phase chromatography showed the correct structure in good quantity. The product obtained was 3,7,ll,15-tetramethylhexadeca-2,5-dien-l-acetate (6), a C2o dienolacetate. 

For industrial hydrogenation of vegetable and animal oils in Russia a Raney type nickel was prepared by Bag and co-workers (64). Preparation of detergents from hydrogenated fats has been reported (11). Reviews of these so-called skeleton catalysts were published by Russian investigators, for instance, by Lel chuk and co-workers (197). These catalysts have also been discussed with reference to hydrocarbon synthesis from water gas (148). Lel chuk (197) states that Raney nickel is more drastic for water gas synthesis than are the skeleton nickel catalysts prepared by Bag, and that Bag s copper-nickel skeleton catalysts approach nickel in their activity. Destructive hydrogenation under mild conditions was said to be possible with Bag s skeleton catalyst as described by Lel chuk. 

Del6pine and Horeau (21) and Reichstein and Gatzi (22) received good results using small amounts of Raney nickel catalyst prepared in amounts just sufficient for use. The procedures consumed very little time because of the small quantities concerned. The advantage of always working with freshly prepared catalyst is obvious. 

Molina, R., M. A. Centeno, and G. Poncelet, a-Alumina-Supported Nickel Catalysts Prepared with Nickel Acetylacetonate. 1. Adsorption in the Liquid Phase , J. Phys. Chem. B. 1999,103, 6036-46. 

Table 3. Results of various nickel catalysts prepared by impregnation method using... 

Approximately 9 parts by weight of the oxime of phenylpropanone was dissolved in approximately 60 parts by weight of 95% ethanol, containing 5 parts by weight of a nickel catalyst, prepared by dissolving aluminum from a nickel-aluminum alloy by means of caustic alkali. The resulting mixture was sealed in a bomb under a hydrogen pressure of 1880 lbs. per sq. in. and reduction was effected for a period of 3-1/3 hrs. at a temperature of 25° C., at the conclusion of which period the pressure was found to have dropped to approximately 1680 lbs. per sq. in. The pressure was then released and the catalyst removed by... 

Fonseca, A. and Assaf, E.M. Production of the hydrogen by methane steam reforming over nickel catalysts prepared from hydrotalcite precursors. Journal of Power Sources, 2005, 142 (1-2), 154. 

Almost all the supported nickel catalysts prepared by the methods mentioned above have a chemical structure more or less similar to that pictured in Fig. 5. 

Nickel catalysts (a), Raney type. The Raney Catalyst Division and the Davison Chemical Division of W. R. Grace and Co. supply an identical 50% sponge nickel catalyst prepared by the method of Raney by leaching 1 1 nickel-aluminum alloy with alkali. The catalyst is similar to the W-catalysts described in the next section. Harshaw Chem. Co. supplies similar nickel catalysts. Universal Oil Products Co. catalyst kieselguhr pellets are reduced with hydrogen and pulverized before use (.see Org. Syn., Coll. Vol., 3,278 (1955). 

Table I summarizes the characteristics of nickel catalysts prepared onto these supports. For brevity these catalysts will be referred to by a notation in the form aA-fi. For example, 7AAP-573 represents a 7 wt % Ni catalyst supported on A O 2A1P0 reduced at 573 K for 1 h. Incidentally, this sample did not reduce under these conditions and was excluded from further kinetic studies. Notations for the other catalysts are shown in the first column of Table I. All samples were reduced at the specified temperature for 1 h unless noted otherwise. The percent reduction was determined by measuring oxygen uptake at 673 K in a commercial thermogravimetric system (Cahn 113). The average particle size was determined by either X-ray diffraction line broadening or magnetic measurements (see below).

Modified nickel catalysts were prepared from the various nickel sources (Table 1). In the case of the modified nickel catalysts prepared from NiO, e.d. ability of the catalyst depended on the NiO manufacturers. These phenomena were also observed for the e.d. hydrogenation of methyl acetoacetate (MAA) [6]. Since the method of the NiO preparation presumably affect the percentage of crystallite part of reduced Ni, the types of NiO would reflect the e.d. ability of the catalyst. On the other hand, fine nickel powder (FNiP) gave the e.d. catalyst... 

A chelating diphosphite prepared from biphenol and PCI3 provides a very stable Ni(0) complex that catalyzes the hydrocyanantion of butadiene without excess ligand. Although the stability of this catalyst is enhanced, the amount of butadiene dimerization byproducts is significant. A related nickel catalyst prepared using a chiral chelating diphosphite based on I -2,2 -binaphthol provides enantioselectivity in the hydrocyanation of norbomene. The major product, J -exo-2-cyanonorbomane, was obtained in an enantiomeric excess of up to 38%. 

The results of Hightower and White s work02 confirm those of the earlier workers. With a nickel catalyst prepared by the decomposition of nickel nitrate on porcelain in a current of hydrogen, these workers obtained the following results from single slow passes of the gas mixture over the catalyst at 350° C. ... 

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. 

Couplings. A nickel catalyst prepared from reduction of (dppf)NiCl2 with BuLi has been employed to synthesize aiylalkenes by coupling arylborortic acids with enolphosphates. ... 

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