CoTPP电化学催化还原溴代环己烷的机理

Mechanism Study on Electrochemical Reduction of Co(Ⅱ)TPP/Cyclohexyl Bromide system

以电化学循环伏安、现场ＥＳＲ电化学以及现场薄层电化学方法研究了电生Ｃｏ（Ⅰ）ＴＰＰ与溴代环己烷的反应机制。在ＤＭＦ中，Ｃｏ（Ⅱ）／Ｃｏ（Ⅰ）的氧化还原有明显的催化溴代环己烷还原的特征，反应现场有自由基生成。反应产物之一是Ｃｏ—Ｃ键化合物，可以在－１．３０Ｖ（ＳＣＥ）一电子还原。当存在ＣＨ＿２＝ＣＨＣＮ时，生成另一种Ｃｏ—Ｃ键化合物，该化合物在—１．１０Ｖ（ＳＣＥ）处一电子还原。证明溴代环己烷与Ｃｏ（Ⅰ）ＴＰＰ反应主要是经过形成烷基自由基的机制进行的。

The mechanism of electrochemical reactions of electrogenerated Co(Ⅰ)TPP andcyclohexyl bromide was investigated with cyclic voltammetry,in-situ ESR-spectroelec-trpchemistry and in-situ micro-electrode-CV thin-layer electrochemistry in DMF solution.The redox reaction of Co(Ⅱ)/Co(Ⅰ) parallelly catalyzed the reduction of cyclohexylbromide,and generated both the cyclohexyl radicals and Co-C bond compoundC6H11 Co(Ⅲ)TPP. Further reduction of the Co-C bond compound at-1.30V (SCE ) im-plied an EC mechanism,namely electrochemical reduction followed by Co-C bond splittingreaction which regenerated the cyclohexyl radicals with rate constant of 0. 73s￣(-1). The pres-ence of additional CH_2=CHCN led to the generation of a new Co-C bond compound whichgave rise to a reduction peak at-1. 10V (SCE).A mechanism for the Co(Ⅱ)TPP/cyclo-hexyl bromide system, suggesting that the cyclohexyl bromide primarily reacts with electro-generated Co(Ⅰ)TPP via the production of the cyclohexyl radicals,has been proposed.