Mixed-Anion Salts

The structural properties of the tetrahedral PO , anion are related to those of other tetrahedral oxyanions XO and isostructural series are often found  

Typical crystalline mixed phosphate-sulphates which have been prepared are 

The crystal chemistry of actinide and lanthanide phosphates with mixed cations and anions has been recently reviewed [11,48,63,64,67,68]. 

Well-known examples of mixed silicate-phosphates are provided by two minerals present in basic slags  

Phosphovanadates and phosphochromates which have been studied include Pb3(P04)24(V04)2 2i, Pb4(P04)2Cr04 and Sr4(P04)2Cr04 and Zt2(P04)2(W04). Mixed salts of Sr, Ba and Pb can be 

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Salts with the homoleptic [Au(C=CR)4]- anion have been obtained in only one case (R = Ph), with [nBu4N]+ as the counterion. The synthesis from (Me3P)Au(C=CPh)3 and PhC=CLi followed by precipitation with nBu4N+Br from thf requires carefully controlled conditions. It is accompanied by reductive elimination of diphenyldiacetylene to give [nBu4N]+[Au(G=CPh)2] as the byproduct. The crystal structure of the colorless, diamagnetic mixed-anion salt 2[nBu4N]+[Au(C=CPh)2] [Au(C=CPh)4] has been determined. The anions are linear and square planar, respectively.120... 

The surfactants used in the emulsion polymerization of acryhc monomers are classified as anionic, cationic, or nonionic. Anionic surfactants, such as salts of alkyl sulfates and alkylarene sulfates and phosphates, or nonionic surfactants, such as alkyl or aryl polyoxyethylenes, are most common (87,98—101). Mixed anionic—nonionic surfactant systems are also widely utilized (102—105). 

The preparation and structural characterization of the ions HX2 has been an important feature of such work/ As expected, these H-bonded ions are much less stable than Hp2 though crystalline salts of all three anions and of the mixed anions HXY (except HBrI ) have been isolated by use of large counter cations, typically Cs+ and NR4+ (R = Me, Et, Bu") — see pp. 1313-21, of ref. 23 for further details. Neutron and X-ray diffraction studies suggest that [C1-H - C1] can be either centrosymmetric or non-centrosymmetric depending on the crystalline environment. An example of the latter mode involves interatomic distances of 145 and 178 pm respectively and a bond angle of -168 (Cl- -Cl 321.2pm).( >... 

The method developed by Epton [212,213] became the universally accepted method for the analysis of active matter of anionic and cationic surfactants. Epton s method, also known as the two-phase titration, is based on the titration of the anionic surfactant with cetylpyridinium bromide, a cationic surfactant, in the presence of methylene blue as indicator. A solution of the anionic surfactant is mixed with the indicator dissolved in dilute sulfuric acid, followed by further addition of chloroform, and then it is titrated with the cationic surfactant. Methylene blue forms a complex with the anionic salt that is soluble in chloroform, giving the layer a blue color. As the titration proceeds there is a slow transference of color to the water layer until the equivalence point. At the equivalence point colors of the chloroform and water layers are visually the same. On successive additions of titrant the chloroform layer lightens in shade and finally becomes colorless. 

From the neutral 1 2 complexes introduced before, two kinds of materials were obtained by electrocrystallization fully oxidized salts where both TTF CH= CH—py moieties are oxidized, and mixed valence salts in which the two ligands are partially oxidized. All oxidized complexes were obtained by oxidation at constant current of a neutral 1 2 complex in an electrolyte containing the anions, and using electrocrystallization technique with platinum wires (0 = 1mm) electrodes. 

Let us now look at this slightly more complex case where the Gibbs energy of the components are needed. Until now we have mixed one salt like AC with another like BD. This implies that the fraction of A atoms on the cation sub-lattice has been equal to the fraction of C atoms on the anion sub-lattice. Let us consider a composition like that marked with a cross in Figure 9.8. There are several possible... 

Fig. 4.2 Typical variations in ionic conductivity with composition. In all cases, variations in alkali or silver content are very low compared to the observed variation in log a (a) influence of the network modifier (LijS) (b) influence of a doping salt (c) mixed alkali effect (d) mixed anion effect. References for data are indicated in Souquet and Perera (1990).

As already discussed in Chapter 1, this kind of mixed valence salt becomes conductive due to the transfer of one electron from two BEDT-TTF molecules to the anion layers. However, at the surface, the charge can become unbalanced, resulting is an incomplete CT. This leads to differentiated surface vs. bulk nesting vectors and to the existence of surface CDWs (Ishida et al, 1999). The Peierls transition has also been observed on the a -planes of single crystals of TTF-TCNQ with a variable temperature STM (Wang et al, 2003) and will be discussed in Section 6.1. 

Electrochemical doping of insulating polymers has been attempted for polyacetylene, polypyrrole, poly-A/-vinyl carbazole and phthalocyaninato-poly-siloxane. Significantly, Shirota et al. [91] claim to have achieved the first synthesis of electrically conducting poly(vinyl ferrocene) by the method of electrochemical deposition (ECD) [91]. This is based on the insolubilization of doped polymers from a solution of neutral polymers. A typical procedure applied [91] for polyvinyl ferrocene is to dissolve the polymer in dichlorometh-ane and oxidize it anodically with Ag/Ag+ reference electrode under selective conditions. The modified polymer [91] (Fig. 28) is a partially oxidized mixed valence salt containing ferrocene and ferrocenium ion pendant groups with C104 as the counter anion. 

The solid-state structures of the mixed valence salts containing 1,2,3,5-diselenadiazole [50]i[l(l have been determined by X-ray crystallography <1994CM508>. The molecular (asymmetric) unit consists of a trimeric cation [50]3+ and an associated triiodide anion. Within the cation the mean interannular Se-Se contact is 3.377 A. The trimer units form dovetailed stacks in which consecutive layers are oriented in a transantipodal fashion. This arrangement introduces close interannular contacts between the blocks along the stack, as well as close lateral contacts. 

Fluoride salts with mixed anionic species present also interesting and specific features ... 

Ag(2+ V) in aHF is able to oxidize RuF6 the new Ag2+ salt with mixed anions was obtained AgRuF6BiF6 [33],... 

In four dendrimers terminated by 12 electroactive tetrathiafulvalenyl substituents (160), the three dimensional character of the inter- and intra-den-drimeric charge and eleetron transfer, and hence of the eleetroconductivity, has been assessed by examination of the electronic spectra of their corresponding neutral state and nation, radieal, dication, and mixed-valence salts, including a closed - shell anion (Figure 24). ... 

These builders are generally available as sodium, potassium, or mixed-metal salts, the latter being more soluble in water but also more costly. The widespread use of sodium TPP (STPP) in LADD formulations can be attributed to the many functions it performs during the wash cycle. Besides its efficient sequestration of hardness ions, STPP works to disperse and suspend soils, enhance the surface action of anionic surfactants, solubilize proteinaceous soils, and provide alkalinity and buffering action. Pyrophospates have been included in some LADD formulations because of its better solubility properties relative to tripolyphosphate [20],... 

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