Square-planar cobalt(II) systems have emerged as powerful carbene transfer catalysts for the synthesis of numerous (hetero)cyclic compounds via cobalt(III)–carbene radical intermediates. Spectroscopic detection and characterization of reactive carbene radical intermediates is limited to a few scattered experiments, centered around monosubstituted carbenes. Here, we reveal the formation of disubstituted cobalt(III)–carbene radicals derived from a cobalt(II)–tetraphenylporphyrin complex and acceptor–acceptor λ³-iodaneylidenes (iodonium ylides) as carbene precursors and their catalytic application. Iodonium ylides generate biscarbenoid species via reversible ligand modification of the paramagnetic cobalt(II)–tetraphenylporphyrin complex catalyst. Two interconnected catalytic cycles are involved in the overall mechanism, with a monocarbene radical and an N-enolate–carbene radical intermediate at the heart of each respective cycle. Notably, N-enolate formation is not a deactivation pathway but a reversible process, enabling transfer of two carbene moieties from a single N-enolate–carbene radical intermediate. The findings are supported by extensive experimental and computational studies.

方形平面钴 (II) 系统已成为强大的卡宾转移催化剂，用于通过钴 (III)-卡宾自由基中间体合成大量（杂）环状化合物。反应性卡宾自由基中间体的光谱检测和表征仅限于一些分散的实验，以单取代卡宾为中心。^{在这里，我们揭示了从钴 (II)-四苯基卟啉复合物和受体-受体 λ 3}衍生的二取代钴 (III)-卡宾自由基的形成作为卡宾前体的-碘亚甲基（碘鎓叶立德）及其催化应用。碘鎓叶立德通过顺磁性钴（II）-四苯基卟啉络合物催化剂的可逆配体修饰产生双卡宾物质。整个机制涉及两个相互关联的催化循环，一个单卡宾自由基和一个N-烯醇-卡宾自由基中间体位于每个循环的核心。值得注意的是，N-烯醇化物的形成不是一种失活途径，而是一个可逆过程，能够从单个N-烯醇化物-卡宾自由基中间体转移两个卡宾部分。这些发现得到了广泛的实验和计算研究的支持。