Cation-Radical Salt with iodine

The interhalogens iodine bromide and iodine chloride form stronger charge-transfer complexes than iodine. Therefore, oxidation of suitable substrates should be feasible. In the case of thianthrene, oxidation is very rapid and a cation radical salt with a complex anion is formed (22) (Murata and Shine, 1969). 

The copper-porphyrin complex gives cation radicals with significant reactivity at the molecular periphery. This reactivity appears to be that of nucleophilic attack on this cation radical, which belongs to the -rr type (Ehlinger Scheidt 1999). A new bifunctional tetrathiafulvalene-type donor molecule (D-ct-D) with a copper iodine bridge has recently been synthesized. Its cation radical salt, (D-variable valence (Ramos et al. 1997). 

To our knowledge no reaction of iodide ion as a nucleophile with a cation radical is known. Iodide ion reduces cation radicals very well and is frequently used for the iodimetric assay of cation-radical salts. Since the reduction is reversible and some compounds can be oxidized to the cation radical stage by iodine, an excess of iodide is used. Some cation radicals are also reduced by other halide ions for example, that of 9,10-diphcnylanthracene is reduced by bromide ion (Sioda, 1968), that of perylene by bromide and chloride ions (Ristagno and Shine, 1971b), and thianthrene radical cation to some extent by chloride ion (Murata and Shine, 1969). These reductions, particularly those by iodide ion, reflect again the competition between nucleophilicity and oxidizability of a nucleophile in reactions with cation radicals. 

The insulating oligomers were reacted with iodine to create a new, cation-radical salt structure of high conductivity. The crystal structure of the iodine complex of N,N -diphenyl-p-phenylene diamine (PPAa)cI> 2 partially resolved by Huml and... 

Poly-SchifF bases containing DCZB units in the main chain (26b) were synthesized by the direct polycondensation of rran5-l,2-bis(3-formyl-9-carbazolyl)cyclo-butane with aromatic diamines [217]. Complexation of the polymers (26b) with iodine produces cation-radical salts which result from an electron transfer from DCZB moieties to iodine. The undoped polymers are insula-... 

The stoichiometry in equation (79) is confirmed by the spectroscopic quantification of the dimethoxybenzene cation radical as well as by the earlier observation that the reaction of electron-rich tetraanisylethylene with iodine monochloride produces the iodine dichloride (IClX) salt of tetraanisylethylene dication whose structure has been established by X-ray crystallography,228 i.e.,... 

A species believed to be the monomer cation radical of 9-ethylcarbazole as a green solution in acetonitrile formed by oxidation of 9-ethylcarbazole with iodine-silver(I) perchlorate, was detected by ESR spectroscopy, although the perchlorate of the cation radical could not be isolated subsequent treatment with potassium iodide gave 9,9 -diethyl-3,3 -bicarbazole. The borofluoride salts generated as crystalline materials by oxidation of carbazole or 9-methylcarbazole with tropylium borofluoride in acetonitrile followed by precipitation with methanol are not salts of the monomer cation-radicaP as originally believed. Russian workers have suggested that nitration of carbazole proceeds via a cation radical. ... 

Chemical oxidation of the TTF groups in compounds 34 and 35 has been achieved by reaction with an excess of iodine in dichloromethane solution, leading to new low-energy absorptions in the UV/visible spectra which are diagnostic of TTF cation radicals the broad absorption at = 830 nm for the iodide salt of 35 suggests the formation of aggregated TTF species. A charge transfer complex formed by 35 and tetracyano-p-quinodimethane (TCNQ) has been isolated as an insoluble black powder. The stoichiometry is (35), (TCNQ)3 (i.e. 8 TTF units 3... 

These reactions are related to the reaction of aryl diazonium salts with iodide yielding iodoaryls, the mechanism of which seems to be a one-electron transfer (radical) reaction and not a nucleophilic displacement. Just as iodide is easily oxi- zed to iodine by the aryl diazonium cation, 2.4.6-triphenyl-X -phosphorin is oxidized to the radical cation 58. 

The most common reactions involving nucleophiles and porphyrin systems take place on the metalloporphyrin 77-cation radical (i.e. the one-electron oxidized species) rather than on the metalloporphyrin itself. One-electron oxidation can be accomplished electrochemi-cally (Section 3.07.2.4.6) or by using oxidants such as iodine, bromine, ammoniumyl salts, etc. Once formed, the 77-cation radicals (61) react with a variety of nucleophiles such as nitrite, pyridine, imidazole, cyanide, triphenylphosphine, thiocyanate, acetate, trifluoroace-tate and azide, to give the correspondingly substituted porphyrins (62) after simple acid catalyzed demetallation (79JA5953). The species produced by two-electron oxidations of metalloporphyrins (77-dications) are also potent electrophiles and react with nucleophiles to yield similar products. 

Attempts to convert organic metals into superconductors have also been undertaken. The first organic superconductor was (TMeTSeF) PF6. The transformation took place at 0.9 K and 1 hPa. Substitution of Cl()4 for PF6 led to a superconductor even at normal pressure and temperature of 1.2 K. In addition, the salt of the ET cation radical with iodide was prepared. It also showed superconductivity at normal pressure. Superconductivity temperatures increased up to 7 K with iodine contents. It was established that a semiconducting sample of (ET)J LT (the so-called a-phase) transformed into the superconducting (3-phase upon heating (Baram and others 1986). 

Despite the reactivity of carbazole cation-radicals, that of 9-ethylcarbazole has been trapped by nucleophiles, e.g., I", NO2,475 Thus, iodo and nitro derivatives of 9-ethylcarbazole result, along with 9,9 -diethyl-3,3 -bicarbazole, when 9-ethylcarbazole is oxidized by iodine in the presence of iodide and nitrite.473 Oxidation in the absence of nucleophiles, e.g., by nitrosonium tetrafluoroborate, permits the synthesis of the cation-radical fluoroborate salts of the 3,3 -bicarbazoles476 The reactivity of the cation-radical of 9-vinylcarbazole has been reviewed recently.11,477... 

Salts have been prepared of 249 by oxidation of the heterocycle with SbClj, UClg, and MoOC. The perchlorate of 3,7-dimethoxy-phenothiazine cation-radical was prepared by oxidation using iminoxyl radicals in organic solvents followed by treatment with perchloric acid. " Various salts of 261 and its benzo derivatives and of lO-phenylphenothiazine were prepared by oxidation with iodine and the appropriate silver salt, " and radical salts of phenothiazine drugs have been made by oxidation of the heterocycles with the acid whose counterion was used for the salt perchlorate and sulfate. ... 

In mineral acids, with or without added oxidizer, according to the oxidizing power of the acid, radical-cation and/or dication salts are formed. The ion-radical halides and thiocyanates of nearly 1 1 stoicheiometry can be prepared by mixing solutions of TTT acetate and solutions containing an excess of the sodium or potassium salt of the anion.Simply by mixing TTT with iodine in nitrobenzene, with different proportions of the reagents, two kinds of crystals are obtained with the composition (TTT)I and (TTTlzIj. ... 

Tosyl iodide, which is easily prepared by the reaction of the sodium salt of p-toluenesulfinic acid with iodine, is a useful reagent for cleavage of vinylcyclopropanes, resulting in functionalized 5-iodopent-2-enyl sulfones (Table 6). ° Experimentally, a dichloromethane solution of the vinylcyclopropane was added to tosyl iodide and propylene oxide in dichloromethane at 40°C. The mechanism probably involved both free-radical and cationic intermediates, and was sensitive to solvent polarity. The resulting 5-iodopent-2-enyl sulfones were formed with Z configuration which enabled their use in subsequent base-catalyzed ring-closure reactions. 

The divergent outcome between the reactions of diaryliodonium salts with charged nucleophiles and with neutral nucleophiles was also explained by this model. In principle, the 10-1-3 intermediate, which is formed in the first step of the overall process, can decompose by two routes. When intramolecular rotation is possible, ligand coupling takes place easily. The second possibility is the homolytic cleavage of the iodine-nucleophile bond, leading to a pair of radicals formed by one electron reduction of the iodonium cation. 

Wieland, 1907 Wieland and Wecker, 1910). Oxidation was carried out in an inert solvent such as benzene, from which the salt precipitated. The easier and more reliable preparation of perchlorate salts by the iodine-silver perchlorate method (Weitz and Schwechten, 1926, 1927), to which we have referred earlier (p. 168), allowed a much clearer understanding of the nature of triarylaminium ions to be obtained. Isolation of perchlorates permitted chemical studies, and easy reduction to the triarylamine by iodide ion, ferrous ion, etc., was consistent with the cation-radical view that was developed. The name aminium ion was coined by Weitz. Other salts were prepared such as tritolylaminium picrate (by oxidation of the amine with lead dioxide in the presence of picric acid), and it was also recognized that conjugate anions in salts obtained by oxidation with antimony pentachloride, phosphorus pentachloride and ferric chloride had to be complex anions rather than simple anionic radicals. This is a particularly pertinent point in antimony pentachloride oxidations (p. 165). 

A unique property of metalloporphyrinates is the general stability and longevity of Tc-cation radicals as obtained in organic or aqueous solutions by oxidation with iodine, bromine, iV-bromosuccinimide (NBS), iron (III) salts, or cathodic oxidation. Titration of magnesiumporphyrinates in chloroform/methanol with NBS or iodine, for example, gives a clean and quantitative conversion to the 7i-cation rad-... 

A new class of highly conducting charge-transfer complexes (306 R=H or Me, X = Cl, Br, or I) has been prepared. ° Cyclic voltammetry of the bis(dithiafulvenyl)-derivatives (307) and (308) has been reported.Oxidation of the bis(dithiolan) (309) with iodine in the presence of aluminium chloride yields the crystalline radical cation salt (310). ... 

All of the cation radicals of 1-11 have been isolated as solid perchlorate salts. Compounds 1 ( ) and 2 ( ) are best oxidized by perchloric acid in anhydrous solvents. The cation radicals of 3 (O, 5 (2 ), 7, 8 ( ), 10 ( ), and 11 (10) can be made by oxidation with iodine-silver perchlorate. The crystalline cation radical perchlorates can be separated out or used in mixture with the solid silver iodide. The cation radical of 4 (7) y as well as that of 3( ) is obtained by an interesting disproportionation reaction of the parent compound and its 5-oxide in perchloric acid (eq. 2). The reaction probably involves the dication and the... 

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