REDOX REACTIONS OF COBALT-CYANIDE COMPLEXES .3. REACTION OF CO(CN)5H3- WITH P-BENZOQUINONE

p-Benzoquinone reacts in alkaline solutions with Co(CN)5H3- via two paths: a slow, pH-independent, direct reaction with the hydride species (k1 = 13.5 M-1 sec-1) and a fast reaction with the Univalent cobalt complex Co(CN)54-, formed by the deprotonation of the hydride, The rate constant for the reaction with Co(CN)54- is of the order 109 M-1 sec-1. In both cases (CN)5CoOC6H4OH3- is the only primary product of the reaction. The formal rate constant of the process at pH >9.2 and 0° is k = 13.5 + 8.7 × 104[OH-]. An addition mechanism is proposed for both reaction paths, the direct hydride transfer or an insertion process being excluded. At pH <9, p-benzoquinone is partly reduced in two one-electron steps, (CN)5Co(μ-OC6H4O)Co(CN)5 being the primary product of this reaction path. © 1969, American Chemical Society. All rights reserved.