Complex ions, structures containing

A complex salt is a saline compound having the structure of a combination of two or more salts and that is regarded as the normal salt of a complex acid. Complex salts do not split into a mixture of the constituent salts in solution, but furnish a complex ion that contains one of the bases (e.g., potassium molybdophosphate and potassium platinochlonde). 

A transition-state structure was proposed on the basis of the solid-state structure of [Ni((R,R)-DBF0X)(H20)3](C104)2 (Fig. 1.8). The catalyst-dienophUe complex is thought to be a square-bipyramidal structure containing an octahedral nickel ion. The dienophile adopts an s-cis conformation with the si face shielded by a phenyl group. 

According to X-ray powder diffraction data, compounds RF NbOFs, Cs2NbOF5 [174] and Cs2TaOF5 [176] have similar type structure and are similar to K2GeF6, whereas (NFL,)2NbOF5 crystal structure is similar with Rb2Mo02F4 [184]. The above-mentioned compounds contain isolated NbOF52" complex ions [185]. 

According to the above classification, the structures of LiNb(Ta)F6 and Li2Nb(Ta)OF5 should be composed of lithium cations and isolated octahedral complex ions, Nb(Ta)F6 or Nb(Ta)OF52, respectively. It is known, however, that the structure of these compounds consists only of octahedrons linked via their vertexes in the first case, and via their sides in the second case. The same behavior is observed in compounds containing bi- and trivalent metals. 

Table 55 presents the results discussed above. Fluoride melts containing tantalum contain two types of complex ions, namely TaF6 and TaF72 . The equilibrium between the complexes depends on the concentration of fluoride ions in the system, but mostly upon the nature of the outer-sphere cations. The complex ionic structure of the melts can be adjusted by adding cations with a certain polarization potential. For instance, the presence of low polarization potential cations, such as cesium, leads primarily to the formation of TaF72 complexes, while the addition of cations with relatively high polarization potentials, such as lithium or sodium, shifts the equilibrium towards the formation of TaF6 ions. 

Adding potassium hydroxide, KOH, to a melt containing KF and a 0.1 mol fraction of K2TaF7 leads to the appearance of an additional band at 900 cm 1, as shown in Fig. 79 [342]. This band corresponds to TaO bond vibrations in TaOF63 complex ions. Interpretation of IR spectra obtained from more concentrated melts is less clear (Fig. 80). The observed absorption in the range of 900-700 cm 1 indicates the formation of oxyfluoride polyanions with oxygen bridges. ..OTaO. The appearance of a fine band structure could be related to very low concentrations of some isolated components. These isolated conditions prevent resonance interaction between components and thus also prevent expansion of the bands by a mechanism of resonance [362]. 

We distinguish electrodes consisting of simple oxides, from those consisting of complex oxide systems. The latter include cations of different metals or cations of a given metal in different valence states. An example for the latter type is cobalt cobaltite C03O4 (a spinel structure) containing Co and Co ions. 

A complex ion is one that contains more than one ion. Because of its effect on mobility, complexation, the process by which complex ions form in solution, is very important for heavy metals and may be significant for organic wastes. Heavy metals are particularly prone to complexation because their atomic structure (specifically the presence of unfilled d-orbitals) favors the formation of strong bonds with polar molecules, such as water and ammonia (NH3), and anions, such as chloride (CO and cyanide (CN ). Depending on the chemistry of an injected waste and existing conditions, complexation can increase or decrease the waste s mobility. 

K2Hg(CN)4 and the crown ether dibenzo-18-crown-6 in aqueous ethanol yield the crystalline [K(C2oH2406)]2[I Ig(CN)4]-2I I2C) the structure contains two independent potassium-crown complexes and a distorted tetrahedral Hg(CN)4 entity (rav(l Ig—C) 218.4, rav(C—N) 112.3 pm) which coordinates to one of the complexed K ions through one of the CN ligands (slight lengthening of the C—N bond).116... 

For (203), models indicated that the isomer containing cis-syn-cis hydrogen atoms on the cyclohexane ring should be able to form clam-type complexes, provided the cyclohexane ring is in the flexible or twist conformation. The models suggested that the cavity defined by the ten oxygen donors would be ideal for K+. However, for the potassium and barium thiocyanate complexes, configurations of type (204) do not occur in the solid state. Instead, two molecules of the bis-crown coordinate simultaneously to two alkali metal ions - both these 2 2 complexes have structures of type (205). 

The preparation and reactions of metal cluster ions containing three or more different elements is an area with a paucity of results. The metal cyanides of Zn, Cd (258), Cu, and Ag (259) have been subjected to a LA-FT-ICR study and the Cu and Ag complex ions reacted with various reagents (2,256). The [M (CN) ]+ and [M (CN) +11 ions of copper, where n = 1-5, were calculated to be linear using the density functional method. The silver ions were assumed to have similar structures. The anions [M (CN) +1 of both copper and silver were unreactive to a variety of donor molecules but the cations M (CN) H + reacted with various donor molecules. In each case, where reactions took place, the maximum number of ligands added to the cation was three and this only occurred for the reactions of ammonia with [Cu2(CN)]+, [Cu3(CN)2]+, [Ag3(CN)2]+, and [ Ag4(CN)3]+. Most of the ions reacted sequentially with two molecules of the donor with the order of reactivity being Cu > Ag and NH3 > H2S > CO. 

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