For a variety of organometallic catalytic processes, most notably Suzuki-Miyaura cross coupling reactions, the oxidative addition of aryl and alkyl halides is a key substrate activation step. Demonstration of this fundamental transformation with iron has little precedent, principally due to competing atom-abstraction chemistry. The aryl-substituted bis(imidazol-2-ylidene)pyridine iron dinitrogen complex, (3,5-Me2MesCNC)Fe(N2)2 (3,5-Me2MesCNC = 2,6-(2,4,6-Me-C6H2-imidazol-2-ylidene)2-3,5-Me2-pyridine) reacts rapidly with non-coordinating aryl and alkyl halides (R–X) at room temperature to yield the corresponding oxidative addition products, (3,5-Me2MesCNC)Fe(R)(X)(N2), in good yields (70 – 80%). Mechanistic studies, specifically relative rate studies, stereochemical probes, and radical clocks, are consistent with a concerted oxidative addition pathway for aryl halides and a radical pathway for alkyl halides. Further reactivity of the (3,5-Me2MesCNC)Fe(R)(X)(N2) products such as transmetalation and C–C bond forming reductive elimination will also be discussed.

Exploring fundamental reactions relevant to iron-catalyzed cross-coupling: strong-field CNC ligands enable two-electron chemistry

ACS Spring Meeting 2021

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