Arsonium ions studies

In addition to the arsafluorenes the UV spectra of a number of other 2-biphenyl and 2,2 -bridged biphenyl derivatives of arsenic have been studied 205, 489, 490, 491) but in most of these the arsenic was present either as arsonium ions as in (XXIV) or (XXV) or in the pentavalent state. 

At the present time the electrochemistry of immiscible electrolyte solutions is developing mainly on the basis of the studies of the water-nitrobenzene and water-1,2-dichloroethane interfaces. The polarizability ranges of these interfaces in the presence of typical electrolytes (system XV) are about 0.30 V. Extension of these ranges towards negative currents has been achieved by substitution of TBA" ions by tetraphenyl-arsonium ions [145], and by crystal violet cations [133,134]. But the substitution of TPhB ions by dicarboUyl cobaltate (III) anions leads to an extension of the above range towards positive currents [127]. 

Cavicchio c-Y al. (14) studied the reaction of stabilized ylides and related onium salts with tropylium ion and found that the reaction between a tropylium salt and an arsonium ylide led to tra .v-chalcone (48) along with triphenylarsine. 

X-ray and spectroscopic studies indicate that the arsonium halides are ionic. Mc4AsBr consists of tetrahedral Mc4As+ units and separate bromide ions. X-ray structures have also been obtained on a series of tetraphenylarsonium salts. " A regular tetrahedral stmcture is found about the arsenic atom when the counterion is a halide or ion of similar size. However, as the size of the counterion increases, the crystals become more disordered. In solution, tetraphenylarsonium salts are almost completely dissociated, but ion pairing can be significant and is dependent primarily on the dielectric constant of the solution. 

Tetraethylammonium tellurocyanate has been prepared and the electrochemical oxidation of the TeCN anion in acetonitrile studied. The reaction takes place with the transitory formation of the [(TeCN)3] complex ion, which then gives the unstable (TeCN)2 dimer this in turn decomposes into tellurium and cyanogen. Extending the earlier preparation and spectral study of several tetra-halogenoaryltellurates(iv) ArTeX, the ammonium, sulphonium, selenonium, arsonium, and iodonium derivatives have been prepared, thus giving more complete spectral data. ... 

Because of the possibility of ion association and charge transfer the use of conductometric titration is suggested. Preliminary unpublished conductometric studies by the authors on the reaction between bromophenol blue and quaternary ammonium and arsonium salts failed, within the sensitivity of the instrument used, to detect any conductivity changes. The reaction is, however, accompanied by metachromasia and can be followed spectrophotometrically, showing again the complementary nature of the physical methods available. 

It is interesting to note that the very widely used Makosza catalyst , benzyl triethyl ammonium chloride, does not show high efficiency in this study. 4) Phosphonium ions are somewhat more effective and thermally stable than the corresponding ammonium catalysts and both are better than arsonium systems. 5) Substitution of the quaternary ion by alkyl rather than aryl groups yields more effective catalysts. 6) Reaction rates are generally greater in orf/io-dichlorobenzene (and presumably in other chlorocarbon media) than in benzene, and botli are better than heptane. In connection with this latter point, Ugelstad and coworkers have studied the reactions of quaternary ammonium phenoxide ions with alkyl halides in a variety of media and concluded that the... 

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