Chloro-complexes

Thallium lII) chloride, TlCl3,4H20. Formed by passing CI2 through a suspension of TlCl in water. Hygroscopic, loses CI2 at lOO C. The [TlCl2l ion is stable chloro complexes up to [TlClfi] are formed. 

To maintain charge neutrality, additional halide ions (Cl in our example) have to migrate inside the pit tluis increasing tire local chloride concentration and a chloro-complex is fonned. 

The chloro-complex is in equilibrium witli its hydroxo-chlorocomplex and... 

To understand why AgCl shows a more complex solubility relationship than that suggested by equation 8.2, we must recognize that Ag+ also forms a series of soluble chloro-complexes... 

Equation 8.7 explains the solubility curve for AgCl shown in Figure 8.1. As Ch is added to a solution of Ag+, the solubility of AgCl initially decreases because of reaction 8.1. Note that under these conditions, the final three terms in equation 8.7 are small, and that equation 8.1 is sufficient to describe the solubility of AgCl. Increasing the concentration of chloride, however, leads to an increase in the solubility of AgCl due to the soluble chloro-complexes formed in reactions 8.3-8.5. ... 

Nickel and Cobalt. Often present with copper in sulfuric acid leach Hquors are nickel [7440-02-0] and cobalt [7440-48-4]. Extraction using an organophosphoric acid such as D2EHPA at a moderate (3 to 4) pH can readily take out the nickel and cobalt together, leaving the copper in the aqueous phase, but the cobalt—nickel separation is more difficult (274). In the case of chloride leach Hquors, separation of cobalt from nickel is inherently simpler because cobalt, unlike nickel, has a strong tendency to form anionic chloro-complexes. Thus cobalt can be separated by amine extractants, provided the chloride content of the aqueous phase is carefully controUed. A successhil example of this approach is the Falcon-bridge process developed in Norway (274). 

Several processes are available for the recovery of platinum and palladium from spent automotive or petroleum industry catalysts. These include the following. (/) Selective dissolution of the PGM from the ceramic support in aqua regia. Soluble chloro complexes of Pt, Pd, and Rh are formed, and reduction of these gives cmde PGM for further refining. (2) Dissolution of the catalyst support in sulfuric acid, in which platinum is insoluble. This... 

Figure 10,5 Structure of SnCi and some chloro complexes of Sn ,...

The solubility of AS2O3 in water, and the species present in solution, depend markedly on pH. In pure water at 25°C the solubility is 2.16 g per lOOg this diminishes in dilute HCl to a minimum of 1.56g per lOOg at about 3 m HCl and then increases, presumably due to the formation of chloro-complexes. In neutral or acid solutions the main species is probably pyramidal As(OH)3, arsenious acid , though this compound has never been isolated either from solution or otherwise (cf. carbonic acid, p. 310). The solubility is much greater in basic solutions and spectroscopic evidence points to... 

In the thermal production of gold coatings on ceramics and glass, paints are used which comprise Au chloro-complexes and sulfur-containing resins dissolved in an organic solvent. It seems likely that polymeric species are responsible for rendering the gold soluble. 

A chiral titanium complex with 3-cinnamoyl-l,3-oxazolidin-2-one was isolated by Jagensen et al. from a mixture of TiCl 2(0-i-Pr)2 with (2R,31 )-2,3-0-isopropyli-dene-l,l,4,4-tetraphenyl-l,2,3,4-butanetetrol, which is an isopropylidene acetal analog of Narasaka s TADDOL [48]. The structure of this complex was determined by X-ray structure analysis. It has the isopropylidene diol and the cinnamoyloxazolidi-none in the equatorial plane, with the two chloride ligands in apical (trans) position as depicted in the structure A, It seems from this structure that a pseudo-axial phenyl group of the chiral ligand seems to block one face of the coordinated cinnamoyloxazolidinone. On the other hand, after an NMR study of the complex in solution, Di Mare et al, and Seebach et al, reported that the above trans di-chloro complex A is a major component in the solution but went on to propose another minor complex B, with the two chlorides cis to each other, as the most reactive intermediate in this chiral titanium-catalyzed reaction [41b, 49], It has not yet been clearly confirmed whether or not the trans and/or the cis complex are real reactive intermediates (Scheme 1.60). 

The fact that the pH values of the pure metals were lower than the theoretical values was attributed to the formation of hydroxy-chloro complexes of the metal and to the high chloride ion concentration in the pit, and the results highlight the very pronounced decrease in pH that can occur in an occluded cell, particularly when the alloy contains high concentrations of chromium and molybdenum. They also showed that migration of chloride ions into the solution in the pit can result in a 7-12-fold increase in concentration, and that the potential in the pit is in the active region. 

Theory. Cadmium and zinc form negatively charged chloro-complexes which are absorbed by a strongly basic anion exchange resin, such as Duolite A113. The maximum absorption of cadmium and zinc is obtained in 0.12 M hydrochloric acid containing 100 g of sodium chloride per litre. The zinc is eluted quantitatively by a 2M sodium hydroxide solution containing 20 g of sodium chloride per litre, while the cadmium is retained on the resin. Finally, the cadmium is eluted... 

The solution should be free from the following, which either interfere or lead to an unsatisfactory deposit silver, mercury, bismuth, selenium, tellurium, arsenic, antimony, tin, molybdenum, gold and the platinum metals, thiocyanate, chloride, oxidising agents such as oxides of nitrogen, or excessive amounts of iron(III), nitrate or nitric acid. Chloride ion is avoided because Cu( I) is stabilised as a chloro-complex and remains in solution to be re-oxidised at the anode unless hydrazinium chloride is added as depolariser. 

In general, the dimers have three chlorine bridges, and Ru3C18(PBu3)4 resembles the mixed-valence chloro complex Ru3Cl 2. A similar, but less extensively studied, pattern of behaviour has been found with other alkyl phosphines. 

The reaction of the (necessarily) cis-oxalato complex with HCI in the last example, ensures the c/s-configuration for the chloro complex on recrystallization, the thermodynamically more stable fra s-isomer forms. fra s-Rupy4Cl2 has Ru-N 2.079 A and Ru—Cl 2.405 A. An imidazole complex (imH) tra s-[RuCl4(im)2] shows promise as a tumour inhibitor and is currently undergoing preclinical trials [135]. 

Compounds of the type [PeX(R2dtc)2] have been obtained by treating [Fe(R2dtc)3] complexes with concentrated hydrohalic acids. [FeCl(Et2dtc)3] has been studied by Hoskins and White (264) it has a square pyramidal structure, with the chlorine atom at the apex, and with the Fe atom situated 62 pm above the basal plane of the four sulfur atoms. A similar structure is found (265) for the monoiodo derivative [FeI(Et2dtc)2]. The chloro complex has been synthesized (266) by the following reaction. 

There is some uncertainty regarding the validity of the stability constants of chloro complexes of Mn according to other computations Mn is a major inorganic species. 

Each entry has the % of total metal present as the free hydrated ion, then the ligands forming complexes, in decreasing order of expected concentration. For instance, in inorganic freshwater at pH 9, Ag is present as the free aquo ion (65%), chloro-complexes (25%), and carbonato-complexes (9%). 

The oxidation of Cr(Il) by Fe(ril) in perchloric acid is markedly catalysed by chloride ion. Taube and Myers found that Cr(H20)5Cl is formed along with Cr(Fl20)5 as products of the oxidation, the relative proportions of the two species depending on concentrations of H and Cl . The suggestion was made that Cr(H20)5Cl is produced by reaction of Cr(H20)g with a chloro complex of Fe(III), viz. 

The complexes show SmA mesophases, except the 2-fluorohexyloxy derivative, which shows a narrow nematic range and the 2-fluoroiodo derivative, which is not a liquid crystal. The transition temperatures of the chloro complexes compared with... 

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