Oxidation of Nickel II

Under milder oxidation conditions a different product is formed (25, 26), best formulated as [Ni (en)2Nilv(en)2Cl2]Cl4. The magnetic moment is reduced to 0.76 BM and there is an intense intervalence band 

The higher valent nickel complexes with saturated amine donors have little more than a transient existence as independent species in solution and consequently have a limited chemistry. Complexes with stronger donor ligands have a more extensive chemistry. 

There is no evidence that oxidation of [Nim(bpy)3]3+ to give a nickel(IV) species can be effected. Likewise, when one of the pyridine rings is replaced by a benzoyl oxime as in syn-2-benzoylpyridine oxime (bpoH), oxidation, using persulfate in basic solution, is limited to 

The reasons for this change in behavior on going from bpy to bpo and dmg2 are not readily apparent since reduction potential data which would allow comparisons of the complexes are not available for all members of the series. The most obvious change is that the ligands differ in charge and that deprotonation parallels the ability of the complex to accept a loss of electrons. 

The best characterized (35-38) of the oxidized nickel dimethyl-glyoximate species is [Nilv(dmg)3]2-, which can be obtained as the diamagnetic potassium, sodium, or barium salt. Preparation of 

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Apart from the activation of the anode no reagent has to be produced. Nickel peroxide, however, has to be prepared by oxidation of nickel(II)sulfate with sodium hypochlorite. Subsequently the reagent has to be carefully dried and the amount of active oxygen determined by iodometric titration. This must be kept in mind, because small amounts of alcohol need already a relative large amount of nickel peroxide, e.g. 100 mmol alcohol more than 75 g nickel peroxide. For that reason the use of the relative expensive, commercial nickel peroxide is restricted. 

The oxidation of nickel(II) complexes of cyclam and Me6cyclam by NO+ in acetonitrile solutions has been studied by Barefield and Busch.3049... 

Ni(diphos)2X2]C104 X = Cl, Br +3 Prepared by oxidation of nickel(II) complexes with FeCl3-6H20. -= 1-90 3046... 

The oxidation of benzaldehyde is also catalyzed by nickel(II) acetate317a>b. Reaction (237) is faster than reaction (236). Hence, oxidation of nickel(II) is... 

Kinetic studies of the oxidation of nickel(II) dimethylglyoximate by periodate, catalyzed by iridium(IV), has been published recently.629 Additionally, the kinetics and mechanism of iridiu-m(III)- and ruthenium(III)-catalyzed oxidation of isopropyl alcohol by iodosoacetate have been elucidated.630... 

Compounds in which nickel is present in a higher oxidation state than 2+ are uncommon and often relatively unstable. Exceptions are found in sodium and potassium nickel(IY) paraperiodates, which have been described by R y and Sarma1 and which correspond to the formulation Na(K)NiI06-xH20. These compounds are readily prepared by peroxydisulfate oxidation of nickel(II) in the presence of periodate. 

Krautler B, Pfaltz A, Nordmann R, Hodgson KO, Dunitz JD, Eschaunoser A (1976) Experiments on a simulation of the photochemical A/D-secocerrin to corrin cycloisomerization by redox prex esses. Electrochemical oxidation of nickel(II)-l-methylidene-2,2,7,7,12,12-hexamethyl-15-cyano-l,19-secexr)rrinate perchlorate. Helv Chim Ac4a 59 924—937... 

Nitric acid oxidation " of nickel(ii) complexes with ligands of the type (14),... 

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... 

More recently, reductive elimination of aryl ethers has been reported from complexes that lack the activating substituent on the palladium-bound aryl group (Equation (55)). These complexes contain sterically hindered phosphine ligands, and these results demonstrate how steric effects of the dative ligand can overcome the electronic constraints of the reaction.112,113 Reductive elimination of oxygen heterocycles upon oxidation of nickel oxametallacycles has also been reported, but yields of the organic product were lower than they were for oxidatively induced reductive eliminations of alkylamines from nickel(II) mentioned above 215-217... 

Nickel hexacyanoferrate (NiHCF) films can be prepared by electrochemical oxidation of nickel electrodes in the presence of hexacyanoferrate(III) ions,141 or by voltammetric cycling of inert substrate electrodes in solutions containing nickel(II) and hexacyanoferrate(III) ions.142 NiHCF films do not possess low-energy intervalent CT bands, however, when deposited on ITO they are observed to reversibly switch from yellow to colorless on electroreduction.143... 

Kruger, H.-J. and Holm, R. H. (1989) Chemical and electrochemical reactivity of nickel(II,I) thiolate complexes - examples of ligand-based oxidation and metal-centered oxidative addition. Inorg. Chem., 28, 1148-55. 

This oxidation state which resembles Cu(II) may be prepared by electrochemical, photochemicalor pulse radiolytic reduction of nickel(II). Nickel(I) macrocycles are powerful reductants and their spectra and redox potentials have been measured. The reactions of the Ni(I) complexes Ni(tmc) 10 and 11 with RX are similar. 

A complete series of nickel(ii) complexes (136)—(139) has been produced wherein the macrocyclic ligands contain four N-donors and vary stepwise from containing one to four unsaturated N atoms. All the complexes are formally obtained by hydrogenation or oxidative-dehydrogenation of Ni(CR) (138). The complexes of (CR) and (CR -f- 4H) have been reported earlier. [(CR -h 2H)-... 

Ni" forms square-planar bis-complexes with the amidate anions of L-Val, L-Phe, and L-Pro. The structure of bis(Gly)-bis(imidazole)nickel(ii) has been reported and the configuration around the metal atom is cis-O(carboxyl), cis-N(amine), cis-N(imidazole). Tetra- and penta-peptide complexes of nickel(ii) consume oxygen in neutral solutions as the metal ion catalyses peptide oxidation to give a number of products, including amides of amino-acids and peptides, oxo-acids, and C02- ... 

The first definitive case of nickel(II) in a tetrahedral environment was in the spinel NiCtaCh (215) the octahedral sites in the oxide lattice are preferentially occupied by chromium(III) ions, leaving only tetrahedral sites for the nickel(II) ions. 

The tertiary triarsine complexes of nickel(II) halides have been more thoroughly investigated. They have formulas [Ni(TA)X2J, and are not dissociated in solution 15, 192). The fact that oxidation affects the metal but not the arsenic must mean that all arsenic atoms are coordinated to the... 

Nickel (III) Hydroxide. Add bromine water to a precipitate of nickel(II) hydroxide. What happens Write the equation of the reaction. How can you explain the different reaction of ironfll), cobalt(II), and nickel(II) hydroxides with the oxygen of the air Why does the method of preparing cobalt(III) and nickel (III) hydroxides differ from that of preparing iron(III) hydroxide How and why do the acid and basic properties of iron, cobalt, and nickel hydroxides change depending on their oxidation state ... 

Presumably, the same consideration might also explain the trend recorded for the other modified oxides of Table II. The reason why the inversion point has not been reached in those samples containing nominally up to 1 % foreign oxide might be the low temperature at which they have been fired together (600°C.) whereas Fensham (54) finds that a temperature of 1100°C. has to be reached before homogeneous solution of a foreign oxide into nickel oxide can be accomplished. 

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