Halides, cadmium

Table 2. Composition of Copper/Cadmium Halide Photochromic Glass ...

Concentrated, aqueous solutions of ZnCla dissolve starch, cellulose (and therefore cannot be filtered through paper ), and silk. Commercially ZnCla is one of the important compounds of zinc. It has applications in textile processing and, because when fused it readily dissolves other oxides, it is used in a number of metallurgical fluxes as well as in the manufacture of magnesia cements in dental fillings. Cadmium halides are used in the preparation of electroplating baths and in the production of pigments. 

Cadmium halides (chloride, bromide, iodide) react explosively with potassium. No accident has been mentioned with fluoride (but this does not prove anything). 

In terms of their chemical behavior, dialkylzinc compounds generally react to transfer alkyl groups to other metals. Dialkyls of cadmium are usually prepared by the reaction of a Grignard reagent with a cadmium halide. 

Mixed alkyl halide compounds result from the reaction of dialkylcadmium with cadmium halides. 

A few general remarks about homeotect structures. Other important sets of homeotect structure types are those related to disilicide structure types (MoSi2, CrSi2, etc.), cadmium halide structure types, etc. (See Parthe 1964, Hyde and Anderson 1989), or presented by certain groups of compounds such as rare earth trialuminides (Van Vucht and Buschow 1965). 

The properties of Cd species formed by the dissolution of cadmium metal in molten cadmium halides and at electrode interface were investigated [216]. 

Ammines of Cadmium Halides.—Cadmium chloride unites with ammonia with formation of the following compounds Mon-ammino-cadmium chloride, [Cd(NH3)]Cl2 diammino-cadmium chloride, [Cd(NH3)a]Cl2 triammino-cadmium chloride, [Cd(NH3)3]Cl2 letram-mino-cadmium chloride, [Cd(NH3)4]Cl2 hexammino-cadmium chloride, [Cd(NH3)6]Cl2A... 

Zinc Sulphate, Zinc Nitrate—Derivatives of Cadmium. Halides, Cadmium Sulphate, Cadmium Nitrate—Derivatives of Merouric Halides-—Amnrino-mercurio Salts, Ammonolysed Compounds, Millon s Base. 

The markedly greater jump in passing from the fluorides to chlorides than with the other steps in the case of the earths is supposed to be explained by a difference in constitution. There is also a difficulty with the cadmium halides. 

Cadmium is a member of Group 12 (Zn, Cd, Hg) of the Periodic Table, having a filled d shell of electrons 4valence state of +2. In rare instances the +1 oxidation state may be produced in the form of dimeric Cd2+2 species [59458-73-0], eg, as dark red melts of Cd° dissolved in molten cadmium halides or as diamagnetic yellow solids such as (Cd2)2+ (AlCl [79110-87-5] (2). The Cd + species is unstable in water or other donor solvents, immediately disproportionating to Cd2+ and Cd. In general, cadmium compounds exhibit properties similar to the corresponding zinc compounds. Compounds and properties are listed in Table 1. Cadmium(TT) [22537 48-0] tends to favor tetrahedral coordination in its compounds, particularly in solution as complexes, eg, tetraamminecadmium(II) [18373-05-2], Cd(NH3)2+4. However, solid-state cadmium-containing oxide or halide materials frequently exhibit octahedral coordination at the Cd2+ ion, eg, the rock-salt structure found for CdO. 

Cadmium Halides. Cadmium halides show a steadily increasing covalency of the metal—halide bond proceeding from fluoride through to iodide. Bond lengths increase through the series F, 0.197 nm Cl, 0.221 nm Br, 0.237 nm I, 0.255 nm. The fluoride is much less soluble in water than the others (see Table 1) and the Cl, Br, and I compounds dissolve to a significant extent in alcohols, ethers, acetone, and liquid ammonia. Boiling points and... 

Many organocadmium compounds are known but few have been of commercial importance. Wanklyn first isolated diethyl cadmium in 1856. The properties of this and other dialkylcadmiums are listed in Table 4. In general, these materials are prepared by reaction of an anhydrous cadmium halide with a Grignard or alkyUithium reagent followed by distillation of the volatile material in an inert atmosphere or in vacuo. Only the liquid dimethyl compound is reasonably stable and then only when stored in a sealed tube. Dimethylcadmium is mildly pyrophoric in air and produces dense clouds of white, then brown, cadmium oxide smoke, which is highly toxic if breathed (45). When dropped into water, the liquid sinks in large droplets that decompose with a series of small explosive jerks and pops. For this reason, and particularly because of the low thermal stability, most dialkylcadmium materials are prepared and used in situ without separation, eg, in the conversion of acid chlorides to speciality ketones (qv) ... 

Cadmium acetate is a colorant for glass and textiles, a glaze for ceramics where it produces iridescent effects, a starting material for preparation of the cadmium halides, and is an alternative to the cyanide bath for cadmium electroplating. In 1991, cadmium acetate dihydrate sold for 59.50/kg in 2 kg lots of reagent-grade material. 

Metal complexes of several zinc, cadmium and mercury salts with 2-, 3- and 4-cyanopyridine have been reported.495 In none of the complexes was cyanide coordination observed. Zinc halides react with 3- and 4-cyanopyridine, but not with 2-cyanopyridine, to give 1 2 complexes which are assigned a monomeric tetrahedral structure on the basis of IR evidence. The cadmium halides also form 1 2 complexes with all the cyanopyridines, except cadmium chloride, which reacts with 2-cyanopyridine to give a 1 1 complex. The former contain... 

The history of zinc and cadmium halides is long and well documented. 

The solution chemistry of zinc and cadmium halides is a topic of active interest, and numerous studies of the related equilibria shown in Scheme 3, in various solvents S, have been reported. 

An EMF method has been used to study the interaction of ZnCl2 with chloride ion in methanol. It is found that Kx (7.76 x 103 M) is less than K2 (1.74 x 104 M), a finding which is interpreted in terms of passing from an octahedral [ZnCl(MeOH)5]+ species to a tetrahedral [ZnCl2(MeOH)2] complex.967 Related studies have shown that the solubility of cadmium halides in water decreases with increasing pressure.968 969 Anionic [ZnCl3] and [ZnCU]2-species are present in zinc chloride battery electrolyte, and are responsible for the observed negative transference numbers for zinc in aqueous acidic chloride medium.970 In neutral... 

Raman measurements on concentrated aqueous solutions of cadmium halides show the presence of chloro complexes of tetrahedral and octahedral symmetry, but the formation of only tetrahedral bromo complexes.978 A combination of solution and solid state 113CdNMR spectroscopic results have allowed the compilation of 113Cd chemical shifts for the complexes [CdX]+, [CdX2], [CdX3] and [CdXJ2-, for X = Cl, Br or I.979... 

In general, the cadmium halides show in their crystal structure the relation between polarizing effect and si/e of anion. The tluoride has tile smallest and least polarizable anion of Ihe lour and forms a cubic structure, while the mure polarizable heavy halides have hexagonal layer structures, increasingly covalent and al increasing distances apart in inxler down tire periodic table, in solution the halides exhibit anomalous thermal and transport properties, due primarily to the presence of complex ions, such as CDlr and CdBr r. especially in concentrated solutions or those containing excess halide ions. 

In the absence of water, cadmium halides, CdX2, react with organolithium compounds, as shown by the following example ... 

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