A massive structural change accompanies electron capture by the 1,2-dicarba-closo-dodecaborane cage molecule (1). Bimolecular electron transfer (ET) by pulse radiolysis found a reduction potential of E0 = -1.92 V vs Fc+/0 for 1 and rate constants that slowed greatly for ET to or from 1 when the redox partner had a potential near this E0. Similarly, two electrochemical techniques could detect no current at potentials near E0, finding instead peaks or polarographic waves near -3.1 V, which is 1.2 V more negative than E0. Voltammetry could determine rate constants, but only near -3.1 V. DigiSim simulations can describe the irreversible voltammograms but require electrochemical rate constants near 1 × 10-10 cm/s at E0, a factor of 10-10 relative to molecules undergoing facile ET. This factor of 10-10 compared to ∼10-5 for bimolecular ET presents a puzzle. This puzzle can be understood as a manifestation of one of the "Frumkin Effects" in which only part of the applied voltage is available to drive ET at the electrode.