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Nickel

About: Nickel is a research topic. Over the lifetime, 79308 publications have been published within this topic receiving 1210058 citations. The topic is also known as: Ni & element 28.


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Journal ArticleDOI
TL;DR: The mechanistic details of nickel-catalyzed reduction of CO(2) with catecholborane (HBcat) have been studied by DFT calculations and suggested that ligand sterics and metal electronic properties play critical roles in controlling the outcome of the reaction.
Abstract: The mechanistic details of nickel-catalyzed reduction of CO2 with catecholborane (HBcat) have been studied by DFT calculations. The nickel pincer hydride complex ({2,6-C6H3(OPtBu2)2}NiH = [Ni]H) has been shown to catalyze the sequential reduction from CO2 to HCOOBcat, then to CH2O, and finally to CH3OBcat. Each process is accomplished by a two-step sequence at the nickel center: the insertion of a C═O bond into [Ni]H, followed by the reaction of the insertion product with HBcat. Calculations have predicted the difficulties of observing the possible intermediates such as [Ni]OCH2OBcat, [Ni]OBcat, and [Ni]OCH3, based on the low kinetic barriers and favorable thermodynamics for the decomposition of [Ni]OCH2OBcat, as well as the reactions of [Ni]OBcat and [Ni]OCH3 with HBcat. Compared to the uncatalyzed reactions of HBcat with CO2, HCOOBcat, and CH2O, the nickel hydride catalyst accelerates the Hδ− transfer by lowering the barriers by 30.1, 12.4, and 19.6 kcal/mol, respectively. In general, the catalytic role...

155 citations

Journal ArticleDOI
TL;DR: A new pincer-type bis(amino)amine (NN2) ligand and its lithium and nickel complexes, including Ni(II) methyl, ethyl, and phenyl complexes, were synthesized and undergo unprecedented reactions with CH2Cl2 and CHCl3 to cleave all the C-Cl bonds and replace them with C-C bonds.
Abstract: A new pincer-type bis(amino)amine (NN2) ligand and its lithium and nickel complexes, including Ni(II) methyl, ethyl, and phenyl complexes, were synthesized. The Ni(II) alkyl complexes react cleanly with alkyl halides including chlorides to form C−C coupled products and Ni(II) halides. More interestingly, the Ni(II) alkyls undergo unprecedented reactions with CH2Cl2 and CHCl3 to cleave all the C−Cl bonds and replace them with C−C bonds. The reactions are highly selective and lead to the first efficient catalytic coupling of CH2Cl2 with alkyl Grignards. A conversion of 82% and a turnover number of 47 are achieved within minutes. Coupling of CD2Cl2 and 1,1-dichloro-3,3-dimethylbutane with nBuMgCl is also realized. Preliminary mechanistic study suggests a radical initiated process for these reactions.

155 citations

Journal ArticleDOI
TL;DR: In the presence of a bis(1,3-diketonato)nickel(II) complex, various olefins are directly monooxygenated into the corresponding epoxides on treatment with atmospheric pressure of oxygen or air and aldehydes as discussed by the authors.
Abstract: In the presence of a bis(1,3-diketonato)nickel(II) complex, various olefins are directly monooxygenated into the corresponding epoxides on treatment with atmospheric pressure of oxygen or air and aldehydes. Especially, it is noted that bis[1,3-bis(p-methoxyphenyl)-1,3-propanedionato]nickel(II) behaves as an excellent catalyst in the present epoxidation.

154 citations

Journal ArticleDOI
TL;DR: A series of materials containing nickel and aluminium ions has been prepared by coprecipitation with alkaline solutions, under various conditions, from solutions of the nitrates as discussed by the authors, and the composition and structure of the precipitates has been examined using a number of techniques including chemical analysis, X-ray diffraction, thermogravimetry and infrared spectroscopy.
Abstract: A series of materials containing nickel and aluminium ions has been prepared by coprecipitation with alkaline solutions, under various conditions, from solutions of the nitrates. The composition and structure of the precipitates has been examined using a number of techniques including chemical analysis, X-ray diffraction, thermogravimetry and infrared spectroscopy. The precipitates have structures typical of minerals of the hydrotalcite group and particularly of the nickel-aluminium compound, takovite. They consist of brucite-like layers of composition [NixAl1–x(OH)2](1–x)+ and interlayers containing CO2–3, NO–3 or OH– ions, or combinations of these, depending on the preparation conditions, together with molecular water; the anions balance the excess charge of the brucite layers. It is concluded that the aluminium ions are randomly substituted for nickel ions in the brucite layers and that the structure of these layers is independent of the anions in the interlayer. For freshly precipitated samples, 0.5 ⩽x≲ 0.85, but for hydrothermally aged materials, 0.66 ⩽x⩽ 0.75; outside these ranges, boehmite or Ni(OH)2 from as separate phases. The results are compared with those for precipitates prepared from ammoniacal solutions and it is concluded that the two types of material are indistinguishable.

154 citations

Journal ArticleDOI
TL;DR: In this article, x-ray photoelectron spectroscopy (XPS) analysis was performed on pumice-supported nickel catalysts, which were prepared by the method of slow homogeneous precipitation with urea.
Abstract: Pumice-supported nickel catalysts, prepared by the method of slow homogeneous precipitation with urea, were analysed by x-ray photoelectron spectroscopy (XPS). By comparison with similarly prepared silica- and alumina-supported nickel catalysts, a preferential interaction of Ni2+ with Al3+ of the support has been determined. A quantitative XPS analysis indicated large segregation of nickel to the surface. The treatment with H2 at 673 K and 1073 K produced a partial reduction of Ni+2 to Ni0. The extent of the reduction was largest at 1073 K and in this case the reduced Ni in the metallic phase was detectable by x-ray diffraction. A decrease of the Ni 2p/Si 2p intensity ratio occurring in the lower temperature H2-treated catalysts was attributed to diffusion of nickel as Ni2+, as a consequence of a solid-state reaction between nickel ions and support oxides, whereas the decrease of the intensity ratio in the high-temperature reduced catalysts was attributed to sintering of the nickel particles and to diffusion of nickel atoms interacting with oxygen vacancies of the support.

154 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20233,184
20226,229
20211,949
20202,693
20193,234
20183,107