Cobalt Superoxo and Alkylperoxo Complexes Derived from Reaction of Ring-Cleaving Dioxygenase Models with O2

The syntheses and O2 reactivities of active-site models of cobalt-substituted ring-cleaving dioxygenases are presented. The pentacoordinate cobalt­(II)-aminophenolate complex, [Co­(TpMe2)­(tBu2APH)], gives rise to two distinct dioxygen adducts at reduced temperatures. The first is a paramagnetic (S = 1/2) cobalt­(III)-superoxo species that was characterized with spectroscopic and computational techniques. The identity of the second Co/O2 adduct was elucidated by X-ray crystallography, which revealed an unprecedented cobalt­(III)-alkylperoxo structure generated by O2 addition to the metal ion and ligand. These results provide synthetic precedents for proposed intermediates in the catalytic cycles of O2-activating cobalt enzymes.本研究报道了钴取代开环双加氧酶（cobalt-substituted ring-cleaving dioxygenases）活性中心模型的合成及其与O₂的反应性。五配位钴(II)-氨基苯酚盐配合物[Co(TpMe₂)(tBu₂APH)]在低温下可生成两种不同的氧加合物：第一种为顺磁性（自旋量子数S=1/2）的钴(III)-超氧物种，通过光谱与计算技术完成了表征；第二种Co/O₂加合物的结构经X射线晶体学解析，其展现出一种前所未有的钴(III)-烷基过氧结构，该结构由O₂加成至金属离子与配体后形成。上述结果为O₂活化钴酶催化循环中所提出的中间体提供了合成先例。