Nickel intermediate

Hard plating is noted for its excellent hardness, wear resistance, and low coefficient of friction. Decorative plating retains its brilliance because air exposure immediately forms a thin, invisible protective oxide film. The chromium is not appHed directiy to the surface of the base metal but rather over a nickel (see Nickel and nickel alloys) plate, which in turn is laid over a copper (qv) plate. Because the chromium plate is not free of cracks, pores, and similar imperfections, the intermediate nickel layer must provide the basic protection. Indeed, optimum performance is obtained when a controlled but high density (40—80 microcrack intersections per linear millimeter) of microcracks is achieved in the chromium lea ding to reduced local galvanic current density at the imperfections and increased cathode polarization. A duplex nickel layer containing small amounts of sulfur is generally used. In addition to... 

The A3-phospholen sulphides (44), bearing reactive functional groups, may be reduced to the phosphine using nickelocene in the presence of allyl iodide.37 The intermediate nickel complex is decomposed with cyanide to free the functionalized A3-phospholen (45). 

Figure 9.3 pictures the oligomerisation reaction Ni is an abbreviation for the nickel-ligand moiety, kg stands for the rate of the growth reaction, and kt for the rate of the termination reaction. These rate constants are the same for all intermediate nickel alkyls, except perhaps for the first two or three members of the sequence owing to electronic and steric effects. Interestingly, a simple kinetic derivation leads to an expression for the product distribution. One can... 

Organic electroreductive coupling reactions using transition-metal complexes as catalysts have been widely investigated. Reviews on the subject have been published [89, 90]. The method involving the most common transition-metal complexes (nickel, cobalt, palladium) appears to be a useful tool to synthetize heterocycles from organic halides via radical intermediates. Nickel catalyst precursors are nickel(II) salts that are cathodically reduced either to nickel(I) or to nickel(O) and cobalt catalyst... 

Ni(acac)2] reacts with Me3Al and P(cyclohexyl)3 under nitrogen to give [ cyclohexyl)3P 2Ni2N2], the structure of which has been determined. The Ni—N—N—Ni system is linear with an N—N bond length of 1.12 A. Intermediate nickel-methyl compounds can be isolated from the reaction and the... 

One postulated reaction mechanism for electrochemical fluorination involves an intermediate nickel fluoride, with nickel in the oxidation stage +III/ + IV, as the active fluorination agent. The induction period in which the nickel fluoride layer is formed at the nickel surface can thus be explained. A radical fluorination mechanism has also been postulated, with oxidation of the fluoride anion to the radical, or as discussed below in the ECEC mechanism.15 The mechanism of this process is still a matter for debate. Reference should be made to a report that does not support the postulates of this section.21 For partial electrochemical fluorination, the ECEC mechanism is postulated as follows. In the first step the starting material is oxidized at the anode (E = electrochemical step). 

Insertion of carbon dioxide into a nickel-carbon bond has recently been demonstrated. The complex Ni(C2H5)2(bpy), (bpy = 2,2 -bipyridine), reacts with C02 in benzene at 40-50°C as shown in (62a) 141a). The intermediate nickel(II) alkyl carboxylate can then react with additional C02 to form either a dicarboxylate or diethyl ketone, as in (62b) and (62c). 

It has been shown that the addition of HCN to the alkene occurs in a cis (suprafacial) manner.601 This was achieved by the addition of DCN to (E)- -deuterio-3,3-dimethylbut-l-ene, catalyzed by [Ni P(OPh)3 4] (131) (equation 162). This requires retention of configuration at the alkyl carbon atom during the reductive elimination of the product from the intermediate nickel(II)-alkyl complex. A cyanoalkyl complex [Ni(CN)(CHDCHBut) P(OPh)3 2] was proposed as the key intermediate in this process. 

Dibromocyclopropanes with vicinal chloromethoxy or mesyloxymethyl substituents undergo [Ni(CO)4]-induced ring opening-carbonylation in the presence of alcohol or amine, leading to y.S-un-saturated carboxylic acid derivatives selectively via intermediate nickel enolates (equation 115).262 Di-... 

Two groups of workers (40, 41) have demonstrated that the reaction proceeds through the formation of a 77--allylnickel intermediate which absorbs CO to form a nickel acyl complex. This then liberates a molecule of acyl halide which is hydrolyzed by the solvent. The presence of the intermediate nickel acyl complex in solution has been demonstrated... 

The formation of both DVCB and COD directly from butadiene requires that the intermediate nickel complex exist in at least two isomeric forms. 

In addition to its importance in alloys (for example, alnico, vicalloy, and stellite), cobalt is of use as a catalyst in the Fisher-Tropsch process in which carbon monoxide is hydrogenated to a mixture of hydrocarbons. It appears likely here that one or more carbonyl derivatives of cobalt act as intermediates. Nickel is of importance in a number of alloys Monel metal, alnico, stainless steel, etc.). In a very finely divided state Raney nickel), it is of use to the organic chemist in hydrogenation reactions, for it will absorb large quantities of hydrogen gas with probable breakage of the molecules to atoms (p. 27). 

Vinyl carbene intermediates can also be generated from the intermolecular addition of TMS diazomethane onto an alkyne component in the presence of Ni(cod)2 as a catalyst. If a diene moiety is also present, as in 1,6-enyne system 78, reaction of the intermediate nickel carbenoid with this partner gives birth to the fused 5,7-bicyclic system 79 in fair yields (Scheme 34). Several mechanistic scenarios are possible from generic precursor 78, including a metathesis-type sequence to generate a nickelacyclobutane 80, followed by... 

Nickel. The only mention of a nickel-C2 system appears to be as an intermediate in the reactions of NiCl2(PR3)2 (R = Me, Pr, Bu) with C2C12, in which an intermediate nickel(I) species NiCl(PR3) may react with NiCl(C=CCl)(PR3)2 to give NiCl(PR3)2 C=C NiCl2(PR3) (56 Scheme 18).183 Elimination of NiCl(PR3) then generates the observed product, [NiCl(C=CPMe3)(PMe3)2]+. 

In addition, acetone itself reacts with the intermediate nickel complex to form the following compounds. This reaction is similar to the Reformatsky reaction. 

Reduction of Ni L in aqueous media by two-electron reductants such as 1,2- or 1,4-dihydroxybenzene proceeds by consecutive two-electron transfer with formation of nickel(II) intermediates.Nickel(III) complexes with (415) and (416) of formula Ni (HL)(C104)2 and Ni °(HT)(C104)2 have been obtained by oxidation with (NH4)2S20g in borate buffer and alkaline solution respectively of nickel(II) complexes or by exposure of the nickel(IV) complexes to moist air. The g values of the nickel(III) species are gii = 2.03-2.05, g = 2.15-2.16.3 - ... 

Carboxy derivatives of seco-corrin metal complexes can be synthesized as shown in Scheme 17. Using the nickel(II) complex (86), treatment with acetic acid/triethylamine in toluene at 110° gave a 56% yield of the nickel corrin (87), along with about 20% of the decarboxylated uncyclized material (88). This latter observation suggested that the ring closure step precedes decarboxylation in accord with this it was shown that the intermediate nickel 19-carboxy-... 

The intermediate nickelacycles decompose by P-hydride elimination to form mixtures of alkenes. For example, tranj-dimethylsuccinic anhydride reacts with Ni(CO)j(PPh3)2 to form a 10 10 1 mixture of trans-and ds-2-butene and 1-butene (Scheme 4). The formation of these alkenes indicates that an intermediate nickel hydride, such as the one shown in Scheme 4, is involved because control experiments demonstrate that no isomerization of the alkenes takes place under the reaction conditions. ... 

The rate is determined by the formation of the intermediate. Nickel is the most effective catalyst followed by cobalt and then copper. Iridium is also a catalyst, but manganese and iron are not. Dissolved metals have the greatest effect, followed by precipitated metal compounds and metal particles. The effect of particles increases with increasing surface area. 

Isolation of the byproduct L98 (R = CH3, Ri = /1-C3H7) gives evidence in favour of the proposed mechanism. It is difficult to imagine its formation without the existence of the intermediate diarylhydrazone L96 [134, 136], which transforms into (Ni(L95B)] through the intermediate nickel(II) chelate of H3L97 (R = H, Ri = WO-C3H7) [137]. 

Addition of compounds containing divalent sulfur, selenium or tellurium also shortens the induction period and increases the rate of reaction. These compounds are highly active if nickel or cobalt halides are used as catalyst precursors. The increase in the rate of reaction may well be explained by the faster regeneration of the active intermediate nickel carbonyl complexes [370]. 

Transition metal nitrate hydrates are industrially favored precursors for the preparation of supported metal (oxide) catalysts because of their high solubility and facile nitrate removal. The final phase and particle size depend on the experimental conditions, as reported for both supported and unsupported metal nitrates [1-3]. Several authors report that decreasing the water partial pressure during the decomposition of unsupported nickel nitrate hexahydrate, via vacuum or a high gas flow, increases the final NiO surface area [3, 4], The low water partial pressure results in dehydration of the nickel nitrate hydrate to anhydrous nickel nitrate followed by decomposition to NiO. Decomposition at higher particle pressures, however, occitrred through the formation of intermediate nickel hydroxynitrates prior to decomposition to NiO. Thus, NiO obtained via intermediate nickel hydroxynitrate species showed a poorer siuface area (1 m /g) compared to NiO obtained via anhydrous nickel nitrate species (10 mVg) [4]. 

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