A Triplet Iron Carbyne Complex

Tuning the spin state of metal carbynes, which have broad applications in organic synthesis and material science, presents a formidable challenge for modern chemists as the strong field nature of carbyne ligands dictates low-spin ground spin states (S = 0 or 1/2) for known metal carbynes. Through the oxidative addition reaction of a low-coordinate iron(0) N-heterocyclic carbene complex with the C−S bond of a thioazole-2-ylidene, we synthesized the first triplet (S = 1) metal terminal carbyne, an iron cyclic carbyne complex. Different from the classical metal carbynes, the triplet complex features an LXZ-type carbyne ligand and a weak FeC triple bond, which endow it with the unique reactivity pattern of facile carbyne coupling, weak affinity toward nucleophiles, and facial addition reactions with electrophiles.金属卡炔（metal carbynes）在有机合成与材料科学领域拥有广泛应用前景，但其自旋状态的调控对现代化学家而言是一项极具挑战性的课题。究其本质，卡炔配体（carbyne ligands）具备强场特性，现有已报道的金属卡炔的基态自旋均为低自旋（自旋量子数S=0或1/2）。我们通过低配位零价铁氮杂环卡宾配合物与噻唑-2-亚基的碳硫键发生氧化加成反应，成功合成了首例三重态（自旋量子数S=1）金属端基卡炔配合物——环状铁卡炔配合物。与经典金属卡炔不同，该三重态配合物含有LXZ型卡炔配体与弱Fe≡C三键，这赋予其独特的反应模式：便捷的卡炔偶联反应、对亲核试剂较弱的亲和力，以及可与亲电试剂发生面式加成反应。