Crystal structure cadmium chloride

Many studies on the direct reaction of methyl chloride with silicon-copper contact mass and other metal promoters added to the silicon-copper contact mass have focused on the reaction mechanisms.7,8 The reaction rate and the selectivity for dimethyldichlorosilane in this direct synthesis are influenced by metal additives, known as promoters, in low concentration. Aluminum, antimony, arsenic, bismuth, mercury, phosphorus, phosphine compounds34 and their metal complexes,35,36 Zinc,37 39 tin38-40 etc. are known to have beneficial effects as promoters for dimethyldichlorosilane formation.7,8 Promoters are not themselves good catalysts for the direct reaction at temperatures < 350 °C,6,8 but require the presence of copper to be effective. When zinc metal or zinc compounds (0.03-0.75 wt%) were added to silicon-copper contact mass, the reaction rate was potentiated and the selectivity of dimethyldichlorosilane was enhanced further.34 These materials are described as structural promoters because they alter the surface enrichment of silicon, increase the electron density of the surface of the catalyst modify the crystal structure of the copper-silicon solid phase, and affect the absorption of methyl chloride on the catalyst surface and the activation energy for the formation of dimethyldichlorosilane.38,39 Cadmium is also a structural promoter for this reaction, but cadmium presents serious toxicity problems in industrial use on a large scale.41,42 Other metals such as arsenic, mercury, etc. are also restricted because of such toxicity problems. In the direct reaction of methyl chloride, tin in... 

Analysis of the Structures. In the following, questions concerning the stereoregularity of the polymer and the origin of the photoinactivity of the copper salts will be answered. For this purpose, the crystal structures of the reactive cadmium chloride complex salt 2 as monomer and polymer, and of the corresponding copper salt i. have been solved by x-ray diffraction. 

To meet the difficulties presented by metal systems, various wider definitions of chemical combination in terms of crystal structure have been proposed. For example, it has been suggested that we should regard an ideal chemical compound as one in which structurally equivalent positions are occupied by chemically identical atoms, and an ideal solid solution as a structure in which all atoms are structurally equivalent. It is clear that such a definition of chemical combination embraces all the generally accepted compounds, but it is not without objection when applied to metal systems. Thus, to take only one example, the ft phase in the silver-cadmium system already discussed has, in its ordered state, the simple caesium chloride structure and must therefore... 

Partin D, O Keeffe M (1991), The structures and crystal chemistry of magnesium chloride and cadmium chloride , J. Solid State Chem., 95(1), 176-183. 

The crystal structure of ammonium cadmium chloride, NH4CdCl3. J. Am. Chem. Soc. 60 (1938) 2886-2890. (Henri Brasseur and Linus Pauling). 

Cadmium is a transition metal in group IIB of the periodic table of elements. The metal is bluish-white to silver-white. At room temperature, it has a hexagonal close-packed crystal structure. Eight stable isotopes are known to be present in natui . The atomic weight of cadmium is 112.4 and the atomic number 48. The density at 25°C is 8.6 g/cm the melting point 321°C and the boiling point 765°C. The most common oxidation state is +2. " The most important compounds are cadmium acetate, cadmium sulfide, cadmium sulfoselenide, cadmium stearate, cadmium oxide, cadmium carbonate, cadmium sulfate, and cadmium chloride. The acetate, chloride, and sulfate are soluble in water, whereas the oxide and sulfide are almost insoluble. ... 

The radius ratios for sphalerite and wurzite type crystals with eighteen-shell cations do not conform to our criterion, so that some other influence must be operative. Without doubt this is deformation. Here again it is seen that the tetrahedral structure is particularly favorable to deformation, for the observed Zn++—O distance (1.93 A.) is 0.21 A. shorter than the theoretical one, while in cadmium oxide, with the sodium chloride structure, the difference is only 0.01 A. 

Cadmium Hydroxide. Cd(OH)2 [21041-95-2] is best prepared by addition of cadmium nitrate solution to a boiling solution of sodium or potassium hydroxide. The crystals adopt the layered structure of Cdl2 there is contact between hydroxide ions of adjacent layers. Cd(OH)2 can be dehydrated to the oxide by gende heating to 200°C it absorbs C02 from the air forming the basic carbonate. It is soluble in dilute acids and solutions of ammonium ions, ferric chloride, alkali halides, cyanides, and thiocyanates forming complex ions. 

The halides of cadmium demonstrate the effect on structure of the easier polarisation of an anion by a smaller cation. Cdp2 has the cubic fluorite lattice but the chloride, bromide and iodide form hexagonal crystals based on layer lattices (p. 150). The distances between the layers increase from the chloride to the iodide, with a corresponding reduction in lattice energies. 

The picture below shows part of the structure of a crystal of CdCh. The layers in the picture continue longways and sideways, and the stack of layers upwards and downwards. Each cadmium ion (green) is surrounded by six chloride ions (blue), but each chloride ion has three cadmium ions on one side, and three chloride ions from the next layer on the other side. 

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