Generation and Characterization of the Tris(pentafluorophenyl)borane Radical Anion

The anion derived from B(C 6 F 5 ) 3 has been detected by EPR, and the boron and fluorine hyperfine splitting constants have been determined. Treatment of B(C 6 F 5 ) 3 with the reductant Cp* 2 Co in THF at −50 °C rapidly results in a dark blue (λ max = 603 nm) paramagnetic solution containing the anion radical. The half-life for disappearance of λ max, about 10 min at room temperature, is consistent with that of the EPR signal.