Tetraphenylarsonium permanganate

Arsonium salts have found considerable use in analytical chemistry. One such use involves the extraction of a metal complex in aqueous solution with tetraphenylarsonium chloride in an organic solvent. Titanium (TV) thiocyanate [35787-79-2] (157) and copper(II) thiocyanate [15192-76-4] (158) in hydrochloric acid solution have been extracted using tetraphenylarsonium chloride in chloroform solution in this manner, and the Ti(IV) and Cu(II) thiocyanates determined spectrophotometrically. Cobalt, palladium, tungsten, niobium, and molybdenum have been determined in a similar manner. In addition to their use for the determination of metals, anions such as perchlorate and perrhenate have been determined as arsonium salts. Tetraphenylarsonium permanganate is the only known insoluble salt of this anion. 

After irradiation and cooling, samples are dissolved in acid and carrier added. Separation of manganese can be made by precipitation as tetraphenylarsonium permanganate (Cotzias et al.. 1966) or manganese dioxide (Miyata et al., 1983) by extraction at pH 8 into chloroform with 8-hydroxyquinoline (Versieck et al.. 1973) or with diethylammonium diethyidithiocarbamate (Damsgaard et al., 1973) by separation with anion exchange resin (Miyata et al., 1973) and after removal of alkali metal salts on a hydrated antimony pentoxide (HAP) column (Miyata et al., 1973). Addition of another manganese isotope ( Mn) can be used to check recoveries of separation procedures. 

These include the simplest ion-association systems in which bulky cations and anions are extracted as pairs or aggregates without further coordination by solvent molecules. An example of this type of system is the extraction of manganese or rhenium as permanganate or perrhenate into chloroform by association with the tetraphenylarsonium cation derived from a halide salt... 

The internal vibrations of the MnOi ion seem to be influenced less by the cations than other metal-oxygen vibrations [see(705)]. For example, the isotypical potassium-, rubidium-, cesium-, and ammonium permanganates have practically the same vi and vz frequencies. The difference observed in the case of AgMn04 is explained in Ref. 83). By the large cations, such as tetraphenylarsonium and tetraphenylphosphonium, the vz band is very sharp and well defined. Since these vz bands are not spht as expected it can be concluded that the anion... 

Of a series of quaternary permanganate salts examined as organic oxidants, those of the unsaturated cations benzyltrimethylammonium, benzyltriethylammonium, methyltriphenylphosphonium, ethylenebis(triphenylphosphonium) and hexadecyl-pyridinium all decomposed explosively at —80—90°C, and of tetraphenylarsonium at 120—130°C. The permanganate salts of the saturated cations... 

The permanganate ion was labeled with " Mn. The separation of Mn04 for kinetic determinations was achieved by co-precipitation with tetraphenylarsonium perrhenate, and the activity was determined with a scintillation counter. The rate constant, Arexch = 710 M s at 273 K, was obtained by fitting of the data to Eq. 65... 

Permanganate ion forms ion-pairs with the tetraphenylarsonium [17,18]-, ethylenebis(triphenylphosphonium) [19,20], trimethylenebis(triphenylphosphonium) [21,22], and benzyltributylammonium [23,24]- cations, soluble in chloroform and in other solvents. These compounds are used in the extractive variants of the permanganate method. 

Similarly, the uranyl ion is extracted from aqueous nitrate solution into isobutanol by associating with two nitrate ions (U02 , 2N03 ), with the uranium probably being solvated by the solvent to make it solventlike. Permanganate forms an ion pair with tetraphenylarsonium ion [(C6H5)4As , Mn04"], which makes it organiclike, and it is extracted into methylene chloride. There are numerous other examples of ion-association extractions. 

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