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Abstract C–H functionalization is a highly appealing strategy for accessing complex molecular structures. Herein, we show that π-tethered pincer ligands can engage in C–H activation when coordinated to iron. These reactions result in C(sp2)–C(sp2) bond formation through oxidative coupling and β-hydride elimination/reductive elimination pathways with alkynes and isocyanides. 

Olefin metathesis is one of the most versatile reactions in a synthetic chemist’s toolbox. Metathesis of C=X (X = O, N,(=NR)2) substrates has also been developed; however, the simple cross-metathesis of diazenes and olefins remains unrealized, in part due to the lack of mechanistic information about deactivation pathways for traditional olefin cross-metathesis catalysts. Herein, we report the reactions of [{PC(sp2)P}Fe(NCtBu)(N2)] ([PC(sp2)P] = bis(2-di-iso-propylphosphino)methylene) with cyclic diazenes, and the formation of metathesis-related products. These reactions led to the isolation of a diazametallacyclobutane from diazocine that ring opens to afford an in situ iron imido complex, which undergoes an intramolecular C-H amination to afford an iron-indoline. Restricting this side reaction with dibenzodiazepine led to the formation of an iron imide complex, which was stabilized and characterized by a one-electron oxidation. 

The reactivity of PC_carbeneP iron carbenes, was investigated toward imines, ketones, diazenes, 2-vinylpyridine, and 8-methylquinoline, revealing the directed activation of aryl, vinyl, or benzyl C–H bonds by 1,2-addition across the iron-carbene bond. 

Olefin metathesis catalyzed by iron complexes has garnered substantial interest due to iron’s abundance and nontoxicity relative to ruthenium, yet its full potential remains untapped, largely because of the propensity of iron carbenes to undergo cyclopropanation instead of cycloreversion from a metallacycle intermediate. In this report, we elucidate the reactions of [{PC(sp2)P}Fe(L)(N2)], ([PC(sp2)P] = bis[2-(diisopropylphosphino)phenyl]methylene) with strained olefins, unveiling their capability to yield metathesis-related products. Our investigations led to the isolation of a structurally characterized metallacyclobutane during the reaction with norbornadiene derivatives, ultimately leading to a ring-opened iron alkylidene. These findings provide compelling evidence that iron complexes adhere to the Chauvin olefin metathesis mechanism.