Nickel II salt

Because of ammine formation, when ammonia solution is added slowly to a metal ion in solution, the hydroxide may first be precipitated and then redissolve when excess ammonia solution is added this is due to the formation of a complex ammine ion, for example with copper(II) and nickel(II) salts in aqueous solution. 

Addition of an alkali metal hydroxide solution to an aqueous solution of a nickel(II) salt precipitates a finely-divided green powder. nickel(II) hydroxide NilOHfj on heating this gives the black oxide. NiO. which is also obtained by heating nickel(II) carbonate or the hydrated nitrate. Black nickel(II) sulphide, NiS, is obtained by passing hydrogen sulphide into a solution of a nickel(II) salt. 

The reactions of aqueous solutions of nickel(II) salts with hydroxide ions, with excess ammonia, with sulphide ion and with dimethyl-glyoxime (see above) all provide useful tests for nickel(II) ions. 

Nickel sulfide, NiS, can be prepared by the fusion of nickel powder with molten sulfur or by precipitation usiag hydrogen sulfide treatment of a buffered solution of a nickel(II) salt. The behavior of nickel sulfides ia the pure state and ia mixtures with other sulfides is of iaterest ia the recovery of nickel from ores, ia the high temperature sulfide corrosion of nickel alloys, and ia the behavior of nickel-containing catalysts. 

Nickel peroxide is a solid, insoluble oxidant prepared by reaction of nickel (II) salts with hypochlorite or ozone in aqueous alkaline solution. This reagent when used in nonpolar medium is similar to, but more reactive than, activated manganese dioxide in selectively oxidizing allylic or acetylenic alcohols. It also reacts rapidly with amines, phenols, hydrazones and sulfides so that selective oxidation of allylic alcohols in the presence of these functionalities may not be possible. In basic media the oxidizing power of nickel peroxide is increased and saturated primary alcohols can be oxidized directly to carboxylic acids. In the presence of ammonia at —20°, primary allylic alcohols give amides while at elevated temperatures nitriles are formed. At elevated temperatures efficient cleavage of a-glycols, a-ketols... 

The dianionic triple-decker species 25 in the presence of cobalt(II) and nickel(II) salts, molecular oxygen, and [(i7 -Cp )Co(C2Et2BHX)] (X = H,... 

Jfickeloxydul, n. nickelous oxide, nickel(II) oxide, NiO. -hydrat, n, nickelous hydroxide, nickel (II) hydroxide, -salz, n. nickelous salt, nickel(II) salt, -verbindung,/. nickelous compound, nickel(II) compound. Nickelpapier, n. nickel foil, nickelplattiert, a. nickel-plated. 

The Institut Fran ais du Petrole has developed and commercialized a process, named Dimersol X, based on a homogeneous catalyst, which selectively produces dimers from butenes. The low-branching octenes produced are good starting materials for isononanol production. This process is catalyzed by a system based on a nickel(II) salt, soluble in a paraffinic hydrocarbon, activated with an alkylalumini-um chloride derivative directly inside the dimerization reactor. The reaction is sec-... 

This reaction, like that between Zn and Cu2+, can serve as a source of electrical energy in a voltaic cell The cell is similar to that shown in Figure 18.2 except that, in the anode compartment, a nickel electrode is surrounded by a solution of a nickel(II) salt, such as NiCl2 or NiS04. The cell notation is Ni Ni2+ Cu2+ Cu. 

Methyl-3-formylpyrazole A-phenylthiosemicarbazone, 45, coordinates as a deprotonated NNS tridentate ligand to form the diamagnetic, spin-paired [Ni(45-H)NCS] complex [200]. However, the complexes formed with other nickel(II) salts have stoichiometry [Ni(45)2]A2, where A = Cl, Br, NO3, CIO4, and BF4. These octahedral complexes NNS coordinated neutral hgands have Dq values between 1086 and 1150cm" ... 

In 1968, Eisch and Foxton showed that nickel(II) salts enhance the rate of BU2AIH addition to internal alkynes by a factor of ca. 1000 compared to the process in the absence of a catalyst [26]. Similar catalytic activity of nickel compounds was found for the addihon of aluminum hydrides to alkenes. 

Nickel(II) salts are able to catalyze the coupling of Grignard reagents with alkenyl and aryl halides. A soluble 6 -phosphine complex, Ni(dppe)2Cl2, is a particularly effective catalyst.266 The main distinction between this reaction and Pd-catalyzed cross... 

A) Ziegler method Catalyst systems can be prepared by reacting a nickel(II) salt with an organometallic compound of the main group metals but aluminum is preferred. 

Its synthesis follows the usual pathway of coupling diazotized 4-chloroaniline onto 2,4-dihydroxy-quinoline and subsequently treating the product with a nickel (II) salt. 

A reaction known as diazo group transfer produces diazo barbituric acid from barbituric acid and p-toluene sulfonyl azide. Additional barbituric acid affords azo barbituric acid [7]. Subsequent complexation with a nickel (II) salt yields a greenish yellow pigment. 

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... 

Nickel(lll) oxide, prepared from a nickel(ii) salt and sodium hypochlorite, is used for the oxidation of alkanols in aqueous alkali [46]. Residual nickel(Ii) oxide can be re-activated by reaction with sodium hypochlorite. Nickel oxides have also long been used in the manufacture of the positive pole in the Edison nickel-iron rechargeable battery, now largely superseded by die lead-acid accumulator, and in the Jungner nickel-cadmium batteries used as button cells for calculators [47]. Here, prepared nickel oxide is pressed into a holding plate of perforated nickel. Such prepared plates of nickel(lli) oxide have been proposed as reagent for the oxidation, in alkaline solution, of secondary alcohols to ketones and primary alcohols to carboxylic acids [48]. Used plates can be regenerated by anodic oxidation. 

Concerning the possible reaction mechanism, the activated lithium can both reduce the nickel(II) salt to give nickel(O) and react with the crystallization water present in the metallic salt to produce molecular hydrogen. However, no gas evolution was observed in the reaction, so the hydrogen initially formed was probably adsorbed on the surface of the active nickel to perform like hydrogenation without hydrogen in the sense that no external source of molecular hydrogen was employed. 

Nickel(II) salts, such as NiCl2, NiBr2 and Ni(acac)2, are commercially available in anhydrous form as inexpensive compounds (< 200-300/mol), and some others, such as Ni(0Ac)2-4H20 and Ni(N03)2-6H20, are also inexpensive but available only as hydrates. Recently, Ni(II) on C was prepared from Ni(N03)2-6H20 and charcoal and used as needed... 

Acetic Acid, Cupric Salt Acetic Acid, Dimethylamide Acetic Acid, Ethyl Ester Acetic Acid, Isobutyl Ester Acetic Acid, Isopropyl Ester Acetic Acid, Methyl Ester Acetic Acid, Nickel (II) Salt Acetic Acid, Propyl Ester Acetic Acid, Sec-Butyl Ester Acetic Acid, Zinc Salt Acetic Aldehyde Acetic Anhydride Acetic Ester Acetic Ether... 

The coordination process may either stabilize or destabilize aromatic Schiff bases. If nickel (II) salts are added to ammoniacal solutions of salicylaldehyde, the precipitate obtained is the inner complex salt of nickel (II) and salicylaldimine (61). If beryllium chloride is added to the Schiff base derived from 2-hydroxy-l-naphthaldehyde and ethylamine, however, the Schiff base is decomposed and the inner complex of beryllium (II) and 2-hydroxy-1-naphthaldehyde is obtained (59). Here the strength of the coordinate bonds formed with the metal seems to determine which complex will be formed. 

Properties of Nickelfll) Salts. Test the reaction of hydrogen sulphide and sodium sulphide with a solution of a nickel(II) salt. Acquaint yourselfwith the values of the solubility products of nickel and cobalt sulphides. 

Cobalt and Nickel Ammines. First add a little, and then an excess of a concentrated ammonia solution to solutions of cobalt(II) and nickel(II) salts. What do you observe Boil the ammonium solution of the cobalt salt while shaking the test tube (for what purpose ). Explain the changes in its colour. Write the equations of the reactions. 

Another arylation method, in the case of nitrogen heterocycles, does not need a halogenated derivative but a heterocycle activated by triflic anhydride260,261 (reaction 22). Simple aryl halides usually do not react with phosphines and special methods therefore have to be used for their arylation. The most widely used is the complex salt method , in which an aryl halide is heated with a phosphine in the presence of a transition metal such as nickel (II)2e (reaction 23). The catalytic cycle probably takes place by means of a reduced nickel(I) complex, generated in situ from the starting nickel(II) salt this nickel(I) species could undergo an oxidative addition of the aryl halide to yield a transient nickel(III) adduct, which after the reductive elimination of the aryphosphonium affords the recovery of the first active-nickel(I) complex (reaction 24). 

Hydrated nickel(II) salts in the presence of the ligand p3 react with both white phosphorus and yellow arsenic, breaking up the structure of the tetraatomic P4 and As4 molecules to form triatomic cyclo-triphosphorus and cyc/o-triarsenic species. These fragments act as trihapto ligands yielding double sandwich complexes (equation 99).292 The compounds are air-stable both in the solid state and in solution. Upon reduction with NaBH the complexes of equation... 

The mononuclear species [Ni(p3)(r/3-P3)]+, which could not be obtained by the reaction of a nickel(II) salt with P4, was obtained by die reaction outlined in equation (102) through the cleavage of the P4S3 cage molecule.297... 

When nickel(II) salts containing a coordinating anion (halide and pseudohalide) are reacted with NaBH4 in the presence of np3, trigonal bipyramidal nickel(I) complexes of the type [NiXnp3], in which the coordinating anion occupies die axial position, 39,340 are obtained. When nickel(II) salts with poorly coordinating anions are used, non-stoichiometric hydrido complexes of nickel(II) are obtained (equations 108 and 109). 

Ammonia complexes can be prepared by addition of ammonia solutions to aqueous solutions of nickel(II) salts.636 Monodentate primary and secondary alkylamines require anhydrous reaction conditions and tertiary amines have only a very slight tendency to form complexes.637,638 Few examples of nickel(II) complexes with MejN and Et3N have been reported.639,640... 

Scheme 3 Some reactions of the naphthyridine ligand (L) and nickel(II) salts...

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