Comparison of the Conductivity Properties of the Tetrabutylammonium Salt of Tetrakis(pentafluorophenyl)borate Anion with Those of Traditional Supporting Electrolyte Anions in Nonaqueous Solvents

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Abstract
Cyclic voltammetry experiments at minielectrodes exhibit less ohmic error for lower polarity solvents when the supporting electrolyte anion is [B(C6F5)4]- rather than one of the smaller traditional anions such as [BF4]-, [PF6]-, or [ClO4]-. Conductance measurements have been performed for [NBu4][B(C6F5)4] in tetrahydrofuran, dichloromethane, benzotrifluoride, and acetonitrile and compared with results for [NBu4]+ salts of several traditional anions in the same solvents. In solvents with dielectric constants of 10 or less, ion association constants, KA, are as much as 2 orders of magnitude lower with [B(C6F5)4]-, TFAB, as the electrolyte anion and the degree of this lowering is related to the acceptor property of the solvent. Analyses carried out on the basis of a Fuoss model attribute this fact to differences in concentrations of contact ion pairs rather than of solvent-separated ion pairs. The greater dissociation of the TFAB ion is attributed to its highly delocalized charge.

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