Organometallic Electrochemistry Based on Electrolytes Containing Weakly-Coordinating Fluoroarylborate Anions

摘要

Electrochemistry is a powerful tool for the study of oxi-ndative electron-transfer reactions (anodic processes). Sincenthe 1960s, the electrolytes of choice for nonaqueous electro-nchemistry were relatively small (heptaatomic or smaller) inor-nganic anions, such as perchlorate, tetrafluoroborate, ornhexafluorophosphate. Owing to the similar size-to-charge ratiosnof these “traditional” anions, structural alterations of the elec-ntrolyte anion are not particularly valuable in effecting changesnin the corresponding redox reactions. Systematic variations ofnsupporting electrolytes were largely restricted to cathodic pro-ncesses, in which interactions of anions produced in the reac-ntions are altered by changes in electrolyte cations. A typicalnladder involves going from a weakly ion-pairing tetraalkylam-nmonium cation, [N(CnH2n 1)4] , with n g 4, to more strongly ion-npairing counterparts with n 4, and culminating in very strongly ion-pairing alkali metal ions.nA new generation of supporting electrolyte salts that incorporate a weakly coordinating anion (WCA) expands anodicnapplications by providing a dramatically different medium in which to generate positively charged electrolysis products. Anchain of electrolyte anions is now available for the control of anodic reactions, beginning with weakly ion-pairing WCAs,nprogressing through the traditional anions, and culminating in halide ions.