Intramolecular Electron Transfer Through a Bridging Carboxylate Group Coordinated to Two Cobalt(III)‐Ions: A Pulse Radiolytic Study

Reduction of the binuclear μ‐p‐nitrobenzoato‐di‐μ‐hydroxo‐bis[triamminecobalt(III)] cation with (CH3)2COH radicals yields a radical cation with the p‐nitrobenzoato radical being coordinated to two cobalt(III) ions at the carboxylic group. The unprotonated form of this species undergoes intramolecular electron transfer producing Co(II) (k = (3.3 ± 0.3) · 103 s−1). The role of the carboxylate group in the intramolecular electron transfer process is tentatively assessed in terms of an intramolecular outer‐sphere reaction because of lack of overlap of the donor orbitals (π) and the acceptor orbital (σ). The protonated form of the radical cation (pKa = 2.5) disproportionates via a bimolecular process without production of Co(II). The effect of two coordinated Co(III) ions as compared to only one on the properties of the nitrobenzoate radical anion are discussed.