Perchlorate as counter-ion

Using a glassy carbon electrode modified with a mercury film, Weber et al. [66] measured the association and dissociation rate constants for the complex formed between Pb + and the 18-crown-6 ether. It was found that Pb + forms a complex with 18-crown-6 with a stoichiometiy of 1 1 in both nitrate and perchlorate media. The formation constant, for the nitrate and perchlorate systems are (3.82 0.89) X 10 and (5.92 1.97) x lO mol Ls , respectively. The dissociation rate constants, are (2.83 0.66) x 10 with nitrate and (2.64 0.88) x 10 s with perchlorate as counter ion. In addition, the binding of Pb + with benzo-18-crown-6 embedded in a polymerized ciystalline colloidal array hydrogel has been also analyzed [67]. 

The mass spectra of 2,6-dimethylthio-3-phenylthiopyrylium (56) perchlorate and iodide, and 5-formyl-2-methylthio-3-phenylthiopyrylium (57) perchlorate have been discussed in detail (76BSF1195). With perchlorate as counter-ion, fragments corresponding to oxidation products of thiopyrylium have been found. 

With a strong hydrogen acceptor, tributyl phosphate, as stationary liquid phase, hydrophilic amines have been separated with perchlorate as counter-ion [5]. Owing to the low solubility of tributyl phosphate in the aqueous mobile phase, these systems are stable and have found use in recent applications, as illustrated in Figure 3. 

Neither copper perchlorate nor ferric perchlorate reacts with thiophene to yield a conducting polymer. However, electrically conductive polymers are synthesized by the reaction of 3-methylthiophene or bithiophene with ferric perchlorate. With copper perchlorate, only bithiophene undergoes a simultaneous polymerization and oxidation reaction. X-ray photoelectron spectroscopy of the PT derivatives with perchlorate as counter ion indicates that a significant amount of the chlorine may be covalently bonded to the polymer [288, 574], The electrical conductivity of polymerized bithiophene reaches values as high as 4.5 S cm [574]. 3-Dodecyl-2,2 -bithiophene, 3-(3-phenylpropyl)thiopheneand 3,4-dibutoxythiophene can be polymerized oxidatively using either copper perchlorate, copper tetrafluoroborate, or ferric perchlorate [575]. 

Studies were made with both lithium and sodium perchlorate as counter ions the rates were sensitive to the nature of the cation present, being lower in... 

The complexes formed with diamides, diacetamide [190], di-n-butyramide [191], iV,iV-dimethylacetoacetamide [184], tetramethyl malonamide [185] and tetramethyladi-pamide [192] have been synthesized. The complexes have the general formula Ln(diamide)4(C104)3. In the case of adipamide the complexes had the formulation Ln(diamide)3(C104)3. All the complexes had uncoordinated perchlorate ion as evidenced by its Td symmetry. With other anions as counter ions the number of coordinated diamide ligands decreased. 

Greving et al. analyzed some basic drugs and quaternary ammonium compounds by means of ion-pair chromatography in the straight-phase adsorption mode. Bromide or perchlorate were used as counter-ions in connection with microparticulate silica gel columns. Chloride and iodide were less suitable as counter-ions, because they caused, respectively, corrosion of the equipment or a too strong UV absorption background of the mobile phase. Methanol was used as mobile phase, containing 0.01-0.1 M of the counter-ion. 

The thianthrene cation-radical (56) shows enhanced stability in trifluoro-acetic acid, which is recommended generally as a solvent in which to prepare cation-radicals. Thianthrenium perchlorate (56 C10 as counter-ion) reacts with substituted benzenes PhR at the para position, rapidly where R = MeO, more slowly where R = Me. The product is a sulphonium salt (58). Kinetic studies show that the reaction is second-order in the thianthrene cation-radical (56). The suggested mechanism features the thianthrene dication (57) as the reactive species, formed in low concentration by disproportionation of the thianthrene cation-radical. 

Doping of PBT with lithium perchlorate, LiC104, (Li" as counter ion) is ineffective in acetonitrile and propylene carbonate, but it is successful when the effective radius of the lithium ion is increased by using hexamethylphosphoric acid triamide as a solvent with high solvating power [250]. 

A third-order rate-determining step involving iron(ii), ClOj, and a proton is suggested, and slight differences in rate have been noted using Li+ and Na+ as counter-ions in the perchlorate electrolyte. Chloride ion has been shown to inhibit the vanadium(iv)-chlorate redox reaction. When the VO + ion is present in excess, in the presence of initially added chloride ion, the stoicheio-metry is four, whereas in the absence of initial Cl, 5 moles of reductant are required. The rate law imder both conditions is of the form... 

To circumvent the ionic influence, anions such as perchlorates and tetraphenylbo-rates were often used as counter ions as they are assumed to have a low basicity and thus not influencing the donor and acceptor properties of solvents significantly.The first estimation of donor numbers for anions was based on the measurement of the free energies (i.e., equilibrium constant) of the reaction [VO(acac)2(MeCN)] + D ca [VO(acac)2D] +... 

When the base is in the form of a salt of a weak acid, removal of an anionic counter ion prior to titration is not necessary, e.g. for salts of bases with weak acids such as tartrate, acetate or succinate. However, when a base is in the form of a chloride or bromide salt, the counter ion has to be removed prior to titration. This is achieved by addition of mercuric acetate the liberated acetate is then titrated with acetous perchloric acid. This is illustrated in Figure 3.9 for the example of phenylephrine.HCl. 

Perchlorate salts of metal complexes are liable to detonate. Perchlorate has been a popular counter ion for metal complexes, but safer ions, such as tetrafluoroborate or hexafluorophosphate, can generally take its place. 

Druy et al.562) showed that iodine- and perchlorate-doped samples lose conductivity quite rapidly in vacuum, due to reaction of the polymer with the counter-ion. Yang and Chien 56l) also observed the instability of these doped polymers and showed that the reaction of polyacetylene with perchlorate counter-ions can be explosive. They showed that doped samples are much more stable to oxygen than is the undoped material. Muller et al.565) also observed that the stability of polyacetylene in air depends on the extent of doping, as did Ohtsuka et al.566). Aldissi 5671 has suggested that iodine doped polyacetylene can be stabilized by phenolic antioxidants, although the effect was modest. 

As often is the case (see Chapter 2, Sections 2.2.6 and 2.7), the molecular mechanics analysis above does not include any electrostatic interaction energies. To include these, the charge distribution and the charge compensation by ion-pairing to counter ions (perchlorate) have to be known. Model calculations indicate that an effective charge of around +1.6 per copper site, a value that is expected from thermodynamic considerations, leads to electrostatic repulsion energies of ca. 17 kJ mol-1 and 10 kJ mol-1, respectively, for the folded and stretched conformers. In agreement with the experiment (EPR spectra), this qualitative analysis indicates a preference for the folded structure of A, and for the stretched structure of B1 201. 

Very few binary compounds of this class have been described, but CIO is widely used as a counter ion for the preparation of many of the cationic species of the other neutral ligands, despite the instability that gives some risk of explosion For many years, it was regarded as the standard for non-coordination —especially in aqueous solution—and both the chlorate and perchlorate crystallized from aqueous solution as [Mn(H20)6]X2. However, the anhydrous Mn(C104)2 can be... 

The first systematic study of Zn shieldings by high-resolution pulse FT methods is that by Epperlein et al. (242) The non-linearity of the shift dependence on concentration for a variety of zinc salts is taken as evidence for complexation with the counter-ion through displacement of water molecules from the hexacoordinated hydration sphere. Generally the concentration shifts for the halides follow the order Cl > Br > I whereas nitrate, perchlorate, and sulphate do not show any concentration dependence. 

Observed molar conductivities were analyzed by assuming the ion association (ion-pair formation) between the complex ions and the counter ions in the same manner as described previously. The closest distances of approach of ions (a) in the Robinson-Stokes conductivity equation and in the Debye-HUckel equation were taken as 6.8 and 7.3 A for chlorides and perchlorates of the tris(phen) complexes 6.6 and 7.1 A for those of the tris(bpy) complex, respectively, using the effective ionic radii of the complex ions, shown in T le 1, and those of Cl (1.81 A) and C104 (2.30A). The values of ref were estimated from the ionic partial molar volumes (f i°°) by use of Glueckauf equation. > ... 

Bipyridyl and phenanthroline give polymeric 1 1 complexes with eopper(II) chloride 597). The existence of the dimeric ion [(bipy)Cu(OH)2Cu(bipy)] + in solution has been established 177, 566) and it has been isolated as the lilac perchlorate (498). The species (bipy)Cu + has surprisingly large affinity for ligands other than OH (370). The di-/a-hydroxo cation considered above has now been prepared with a variety of counter ions the corresponding phenanthroline salts are also known. There is no evidence of antiferromagnetic interaction between the copper(II) ions even at 80°K (321). When the counter ion is iodide or thiocyanate there is evidence for metal ion-coimter ion interaction. 

J0rgensen [105] and Lectka [106] have reported the ene reactions of imines. Both used BINAP as ligands, and a variety of copper salts (Sch. 58). The ee of 266 depended on the counter ion on the copper—PFf, and CIO4 anions gave the highest selectivity. It is also important to note that CuPFs is safer to use than the perchlorate. 

The importance of both the cationic and anionic portions of the initiator was revealed by a study of various initiators for THF polymerization having different cations and different counter-ions. In this study, Yamashita et al. [84,85] concluded that the kp value with CH2CI2 solvent at 0°C is almost independent of counter-ion when triethyloxonium ions are used as initiators. They found much slower apparent rates when the different cation initiators, acetyl hexafluoroantimonate and 2-methyl-1,3-dioxolenium perchlorate, were used. They explained the slower rates by decreased rates of initiation. The apparent fep s can be increased to the... 

The structure of tropyl azide, which is synthesized by the action of azide ion on tropylium perchlorate , may be represented as the covalent azidocycloheptatriene (161), the non-benzenoid aromatic tropylium salt with azide as the counter-ion (162), or an equilibrium mixture of the two. Spectroscopic studies by Wulfman and colleagues indicate that in non-polar solvents such as carbon... 

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