Nickel forms

Nickel forms yellow anhydrous halides NiXjlX = F. Cl. Br) and a black iodide Nil2 all these halides are made by direct combination of the elements, and the chloride by reaction of sulphur dichloride oxide with the hydrated salt. All dissolve in water to give green solutions from which the hydrates can be crystallised the solutions contain the ion [NifHjOls], and the chloride crystallises as NiCl2.6H2O, nickel(II) chloride hexahydrate. 

Nickel forms a green hydrated sulphate NiS04. TH O and the double sulphate (NH4),S04. NiS04.6HtO (cf. iron, p. 396). 

Properties. Nickel forms anhydrous as well as hydrated haHdes. The properties of the anhydrous salts are given in Table 1. 

Other simple nickel salts of organic acids include the oxalate [20543-06-0] oleate [68538-38-5], and stearate [2223-95-2]. The latter two have been used as oil-soluble nickel forms in the dyeing of synthetic polyolefin fibers (see Driers and metallic soaps). Nickel oxalate has been used as a catalyst intermediate (59). 

Metals and alloys, the principal industrial metalhc catalysts, are found in periodic group TII, which are transition elements with almost-completed 3d, 4d, and 5d electronic orbits. According to theory, electrons from adsorbed molecules can fill the vacancies in the incomplete shells and thus make a chemical bond. What happens subsequently depends on the operating conditions. Platinum, palladium, and nickel form both hydrides and oxides they are effective in hydrogenation (vegetable oils) and oxidation (ammonia or sulfur dioxide). Alloys do not always have catalytic properties intermediate between those of the component metals, since the surface condition may be different from the bulk and catalysis is a function of the surface condition. Addition of some rhenium to Pt/AlgO permits the use of lower temperatures and slows the deactivation rate. The mechanism of catalysis by alloys is still controversial in many instances. 

During recent years a considerable amount of information has been published on the anodic behaviour of nickel alloys. The data include studies both of binary alloy systems in which nickel forms the major alloying component and of more complex commercially produced nickel alloys. The data are sufficiently numerous to permit a rational and fairly complete interpretation of many of the corrosion-resistant properties of nickel alloys on the basis of their anodic behaviour. 

When stainless steel is struck the passive film is reduced and an adherent flash of nickel forms on the active metal surface. Deposition is continued in a normal bath. 

On heating in air, nickel forms a protective oxide and gives good service up to 700°C. Nickel is not recommended for exposure to chlorine, sulphur dioxide, nitric acid, sodium hypochlorite, mercuric or silver salts. 

Oxidaton of heme goes through the biliverdin species. Octaethylbiliverdin can exist in coordinated form as the fully reduced trianion (OEB)3-, as the two-electron-oxidized monoanion (OEBox), or as the one-electron-oxidized radical (OEB-)2-. Nickel forms complexes with all three moieties, [Nin(OEB)]ra with n I 1, 0, and -1 (689).1787 The most highly oxidized species [Ni(OEBox)]I3 could be crystallized. The structure shows a helical coordination of the linear tetrapyrrole ligand around nickel with Ni—N distances of 1.867 A and 1.879 A. 

Cadmium, along with nickel, forms a nickel-cadmium alloy used to manufacture nicad batteries that are shaped the same as regular small dry-cell batteries. However, a major difference is that the nicads can be recharged numerous times whereas the common dry cells cannot. A minor difference between the two types of cells is that nicads produce 1.4 volts, and regular carbon-zinc-manganese dioxide dry-cell batteries produce 1.5 volts. 

Three-dimensional epitaxial crystallites (TECs) were observed in the first stages of electrodeposition of copper (51) and nickel (58) on copper substrates. TECs of nickel formed on copper-film substrate from nickel sulfate solutions in low concentration are shaped rectangularly with edges averaging 1300 A in length. The coherent... 

Nickel forms a large number of complexes with various anions (monoden-tate, bidentate, and polydentate) and many neutral ligands. The most common coordination numbers of the metal in these complexes are six and four while the metal is usually in +2 oxidation state, Ni2+. Also, some complexes of three and five coordinations exist. Several zero valent nickel complexes, such as nickel tetracarbonyl, and a number of substituted carbonyl complexes are well known. 

Nickel forms useful alloys with many metals. It is added to metals to increase their hardness, strength, and corrosion resistance. The most familiar nickeliferous alloys are stainless steel and coinage metal. 

In natural waters, nickel primarily exists as the hexahydrate. While nickel forms strong, soluble complexes with OH, S04 , and HCQ, these species are minor compared with hydrated in surface water and groundwater with pH <9 (Rai and Zachara 1984). Under anaerobic conditions, such as may exist in deep groundwater, nickel sulfide would control aqueous nickel concentrations to low levels. 

Nickel forms organometallic clusters with three to six metal atoms. Among these some unusual structures and bonding situations occur which were mentioned in Chapter 2. The cluster chemistry of palladium is rather poor, and the outstanding features of platinum are a considerable number of trinuclear heterometallic complexes and the chimney-like structures of the clusters [Pt3(C0)g]. ... 

Chemical Combinations. — Nickel forms two oxides a protoxide, Ni 0—and a sesqmoxide, Nis Oj. 

With its 3d84,r2 electron configuration, nickel forms Ni2 ions. Having a nearly complete 3d subshell, nickel does not yield a 3d electron as readily as iron and cobalt, and trivalent and tetravalent forms are known only in the hydrated oxides. Ni203 and Ni()2. and a few complexes. 

Other elements with which nickel forms binary compounds, especially at higher temperature, are. boron, carbon, nitrogen, silicon, and phosphorus. Like NiO. these compounds may depart slightly or even considerably from daltonide composition, frequently being interstitial compounds, and with higher elements of transition groups 5 and 6, merging into the interstitial compound-solid solution picture which nickel exhibits with the other transition metals. 

Divalent nickel forms two main types of complexes. The first consists of complexes of the spin-free ( ionic or outer orbital) octahedral type (see also Ligand for their discussion) in which the ligands are principally H2O, NH3, and various amines such as ethylenediamine and its derivates, e.g., Ni(H20>62+. Ni(NH3)e2+, Ni(en)62+. These complexes usually have colors toward the high-frequency side of the spectrum, i.e., violet, blue, and green. The other class consists of tetracovalent square complexes with ligands such as CN, the dioximes and their derivatives, and other chelates, which usually have colors on the low frequency side of the spectrum, i.e., red. orange, and yellow. The structure of the nickel-climethylglyoxime complex is... 

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