Direct Influence on Electron-Transfer Equilibrium

a very important factor of preferential dianion formation is the decrease in electrostatic repulsion between anion-radicals. By changing the ion-pair stability, particularly, by solvent selection, one can manage the equilibrium of liquid-phase electron-transfer reactions. 

A special case of disproportionation as a consequence of ion association is mentioned in conclusion. If a suspension of triethyloxonium hexachlorantimonate and tetrakis(anisyl)ethylene. 

An2C=CAn2, is stirred in dichloromethane, their corresponding cation-radical salt forms quantitatively (Rathore et al. 1998)  

Slow crystallization of salt from the reaction solution layered with diethyl ether leads to the formation of a mixture of tetrakis(anisyl)ethylene cation-radical and dicationic salts along with tetrakis( anisyl)ethylene. All the compounds precipitate from the solution containing the cation-radical salt only. The formation of dication is a result of disproportionation. 

two possible causes of this disproportionation should be taken into account—changes in the solution parameters during slow mixing of the solvent layers (dichloromethane and diethyl ether) and requirements with respect to the closest packing in crystals. 

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