Cadmium chloride, structure

Layered structures are extremely prevalent among transition metal halides. Examples of compounds adopting the cadmium iodide structure or the related cadmium chloride structure (Fig. 7.9) are ... 

The cadmium chloride structure differs from that of cadmium iodide only in the geometrical disposition of successive layers these layers are now so arranged that the halogen atoms are in cubic close packing. This close relationship between the two structures is emphasized by the behaviour of CdBr2 and NiBr2. These compounds both have the... 

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. 

Unusual arene-cadmium 7r-complexes have been recently prepared and structurally characterized. For example, the /w /zz-bcn/i porphyrin complex 194, which can be obtained by reaction of the free base with CdCl2, possesses a cadmium atom that is bound to the Mfez-phcnylcnc unit of the ligand in an apparent /-fashion (Figure 32). The resulting Cd-C distance of 2.71 A is shorter than the sum of the van der Waals radii.252 Despite this relatively short contact, DFT calculations and AIM analysis point to the weakness of the interaction. Comparable weak arene-cadmium 7r-interactions are also observed in the /wra-benziporphyrin cadmium chloride complex 195.253... 

Cadmium oxide, CdO, like nickel oxide, also adopts the sodium chloride structure (Fig. 1.14). However, unlike nickel oxide, this compound can be made to contain more metal than oxygen. The defects that cause this metal excess are usually considered to be interstitial Cd atoms or ions. In this case the reaction is one in which the solid formally loses oxygen. Because of the rules of equation writing, this must involve the removal of neutral oxygen atoms. Each oxygen lost results in the loss of a nonmetal site. In order to keep the site ratio correct, a metal site must also be lost, forcing the metal into interstitial sites ... 

Diffusion in the extrinsic region can readily be modified by doping, although knowledge of the mechanism by which the diffusion takes place is important if this is to be immediately successful. For example, sodium chloride structure materials that conduct by a vacancy mechanism can have the cation conductivity enhanced by doping with divalent cations, as these generate compensating cation vacancies. The inclusion of cadmium chloride into sodium chloride can be written ... 

The sodium chloride structure is adopted by most of the alkali metal halides All of the lithium, sodium, potassium, and rubidium halides plus cesium fluoride It is also found in the oxides of magnesium, calcium, strontium, barium, and cadmium... 

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 zinc blende structure of ZnS (3 2PT) has S2- filling ccp P layers and Zn2+ filling one T layer. For Li20 (3 3PTT, the antifluorite structure), the O2- ions fill ccp P layers with Li+ ions filling both T layers. The NaCl structure has the 3 2PO structure, with CP ions filling ccp P layers and Na+ ions filling O layers. Cadmium chloride (CdCh) has a... 

Table Some binary structures based on close-packed arrays of anions Array Holes filled Structure type Examples Fee All octahedral Rock salt (NaCl) LiF, MgO V2 octahedral Cadmium chloride MgCl2...

Fig. 7.9 Layered structure of cadmium chloride. CdCL. Note relationship to extended NaCI structure (missing atoms are dashed). (From Wells. A. F. Siriiciural Inorganic Chemistry, 5th ed. Oxford University Oxford, 1984. Reproduced with permission.)...

Layer structures 6 3 Cadmium iodide (C 6) Cadmium chloride (C19) TiS2, ZrS2, SnS2, PtS2, TaS2, HfS2 TaS2... 

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. 

Many AX2 halides, particularly those of the transition metals, show one or other of the closely related cadmium chloride and cadmium iodide structures. Both of these structures are formed by the superposition of a series of composite layers, each of which consists of a sheet of cadmium atoms sandwiched between two sheets of atoms of the halogen. The arrangement of one such layer is shown in fig. 8.08, and it will be seen that a characteristic feature of the structure is the asymmetry of the co-ordination the cadmium atoms are symmetrically surrounded by six halogen atoms at the corners of an octahedron, whereas the three cadmium neighbours of each halogen atom all lie to one side of it. In cadmium iodide the structure as a whole is built up by the superposition of such layers in identical orientation, and the structure can therefore be described in terms of the very simple hexagonal unit cell... 

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