Reactions of Co(III)–Nitrosyl Complexes with Superoxide and Their Mechanistic Insights

New CoIII–nitrosyl complexes bearing N-tetramethylated cyclam (TMC) ligands, [(12-TMC)­CoIII(NO)]2+ (1) and [(13-TMC)­CoIII(NO)]2+ (2), were synthesized via [(TMC)­CoII(CH3CN)]2+ + NO­(g) reactions. Spectroscopic and structural characterization showed that these compounds bind the nitrosyl moiety in a bent end-on fashion. Complexes 1 and 2 reacted with KO2/2.2.2-cryptand to produce [(12-TMC)­CoII(NO2)]+ (3) and [(13-TMC)­CoII(NO2)]+ (4), respectively; these possess O,O′-chelated nitrito ligands. Mechanistic studies using 18O-labeled superoxide (18O2•–) showed that one O atom in the nitrito ligand is derived from superoxide and the O2 produced comes from the other superoxide O atom. Evidence supporting the formation of a Co–peroxynitrite intermediate is also presented.

新型搭载N-四甲基环拉胺（N-tetramethylated cyclam, TMC）配体的三价钴亚硝酰配合物[(12-TMC)­CoIII(NO)]²⁺（编号1）与[(13-TMC)­CoIII(NO)]²⁺（编号2），通过[(TMC)­CoII(CH3CN)]²⁺与气态一氧化氮（NO）的反应合成。光谱与结构表征结果证实，此类配合物以弯曲端基配位模式结合亚硝酰基团。配合物1与2分别与超氧化钾/2.2.2-穴醚（2.2.2-cryptand）反应，生成[(12-TMC)­CoII(NO2)]⁺（编号3）与[(13-TMC)­CoII(NO2)]⁺（编号4），二者均带有O,O′-螯合型亚硝酸根配体。借助18O标记的超氧阴离子自由基（¹⁸O₂•–）开展的机理研究表明，亚硝酸根配体中的一个氧原子源自超氧阴离子，而生成的O₂则来自另一个超氧阴离子的氧原子。本研究同时还提供了支持Co-过氧亚硝酸根中间体形成的实验证据。