ABSTRACT The cobalt–carbon bond in alkylcobaloximes and in alkylcobalt derivatives of related chelates is reductively cleaved by thiols in mildly acidic medium, or by carbon monoxide, dithionite and stannite in alkaline solution. The reductants interact initially by trans attack of the cobalt atom, followed by the rate-determining cleavage of the Co–C bond. Cobalt-bound methyl groups are converted into methyl carbanions, or species with the reactivity of methyl carbanions, which react with protons of the medium to form methane. In the presence of CO 2 detectable amounts of acetic acid are formed, in accord with this mechanism. The reductive cleavage of organocobalt complexes, derived from vitamin B 12 or vitamin B 12 model compounds, by thiols is correlated with available enzymological evidence on ribonucleotide reductase of Lactobacillus leichmannii. microbial methane biosynthesis of Methanobacillus omelianskii and acetate biosynthesis by Clostridium thermoaceticum. All three enzymatic processes are envisaged to involve reductive Co–C bond cleavage reactions of coenzyme–substrate intermediates as part of the catalytic cycle.

中文翻译：

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维生素 B12 和维生素 B12 模型化合物化学的最新进展：还原性钴碳键裂解反应

摘要 烷基钴肟和相关螯合物的烷基钴衍生物中的钴-碳键在弱酸性介质中被硫醇或在碱性溶液中被一氧化碳、连二亚硫酸盐和亚锡石还原裂解。还原剂最初通过钴原子的反式攻击相互作用，然后是 Co-C 键的决速断裂。与钴结合的甲基转化为甲基碳负离子，或具有甲基碳负离子反应性的物质，它们与介质的质子反应形成甲烷。根据该机理，在CO 2 存在下形成可检测量的乙酸。来自维生素 B 12 或维生素 B 12 模型化合物的有机钴复合物的还原裂解，由硫醇与可用的关于莱氏乳杆菌核糖核苷酸还原酶的酶学证据相关。Methanobacillus omelianskii 的微生物甲烷生物合成和热乙酸梭菌的乙酸盐生物合成。设想所有三个酶促过程都涉及辅酶 - 底物中间体的还原性 Co-C 键裂解反应，作为催化循环的一部分。