Constants halide complexes

We begin by considering the stability constants for the formation of halide complexes with zinc(ii) and mercury(ii) (Table 9-2)... 

Uranium halide complexes, 25 437-439 physical constants for, 25 4371 Uranium hexachloride, 25 439 Uranium hexafluoride, 11 845, 859, 25 438 Uranium hydrocarbyl complexes,... 

One can set up to do this using the competition between dimerization and halogen atom abstraction from RX to form the rhodium(III) halide complex. As a function of [RX], the product ratio is quite easily evaluated. From that, one can get the rate constant ratio but, knowing independently the rate constant for dimerization, it is possible to extract from those data rate constants for reactions of the rhodium(II) complex with these organic halides. The rate constants obtained are listed in Table I. 

Table 51 Stability Constants (Log P) of Cationic Silver Halide Complexes Ag2X+ and Ag3X2+ in Various solvents at 24 "C380...

The stability constants in melts of NH4N03- H20 of ZnX+, ZnX2 (n = 1-3 X = Cl or Br), CdX+, CdX2 (n = 1.5-3 X = Cl or Br) and HgX HgX2 (n = 2.5 X = Cl or Br) have been determined.950,931 The behaviour of zinc is peculiar if the Ki and K2 values are compared with those of cadmium and mercury. The stability constants increase with temperature and the bromide is more stable than the chloride, trends which are opposite to those normally observed for the halide complexes of most metals in anhydrous or aqueous melts. The data also show... 

Much work has been devoted to the halide complexation of these elements in non-aqueous media. Equilibrium and calorimetric measurements for the formation of the [MX ](n-2) (M = Zn or Cd X = Cl, Br, I or SCN n = 1-4) anions in dimethyl sulfoxide (DMSO) have shown that stability constants follow the same order, but are much larger than those found for aqueous solution zinc exhibits an enhanced hardness as an acceptor in DMSO as compared to cadmium. Calorimetric measurements indicate a change from octahedral to tetrahedral coordination with increasing halide concentrations.1002-1006... 

Although the stability constant sequence for halide complexes of many metals is F > Cl > Br > I, Cu1 and Ag1 belong to the group of ions of the more noble metals, for which it is the reverse. 

Table 11.2 gives some stability constants for complexes of Th + and U02 +. Thorium forms stronger complexes with fluoride, the hardest halide ion, than with chloride and bromide this is the behaviour expected of a hard Lewis acid. Thorium also forms quite... 

Maciel et al. (243) have determined the shifts for the halide complexes ZnX " (n = 0,1,2,3,4 X = Cl , Br ) on the basis of the observed dependence of Zn " shieldings on halide concentration and individual formation constants available from other sources. For this purpose they developed a least-squares treatment which has permitted them to fit the experimental shieldings to ... 

For example, [Re (CN)(CO)3(bpy)] in strictly aprotic solvents at low temperature is reduced in two chemically reversible one-electron steps at —1.77 and —2.42 V, which correspond to formation of [Re (CN)(CO)3(bpy)] z = 1— and 2—, respectively [130]. The first reduction of [Re(CO)4(bpy)]+ or [Re(P(OEt3))(CO)3(bpy)]+ is chemically reversible even at room temperature [133, 135]. Halide complexes [Re (X)(CO)3(bpy)] (X = Cl, Br) have a complicated reduction pattern because of further reactions of the reduced products. Several reaction intermediates and products have been characterized spectroelectrochemically [131, 135-137] and rate constants of the main steps have been determined [130] by low-temperature cyclic voltammetry. 

A practical problem frequently encountered by the analytical chemist is that of maintaining as nearly as possible a constant ionic environment while varying the concentration of one component of a mixture of electrolytes. For example, in evaluating the successive formation constants of halide complexes of a metal ion, it is necessary to vary the halide ion concentration over wide limits. The practice generally... 

Sharma V. K. and Millero F. J. (1988d) Determining the stability constant of copper (I) halide complexes from kinetic measurements. Inorg. Chem. 27, 3256-3259. 

Most interesting are the selectivity differences between an alumina phase and a strongly basic anion exchanger with quaternary ammonium groups. In comparison with a conventional anion exchanger, halide ions, for example, are eluted in reverse order I-< Br < Cl < F. This order corresponds to the formation constants of aluminum halide complexes [46], which suggests an interaction between aluminum and halide ions within the A1203 structure. 

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