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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.