Air-Stable Iron-Based Precatalysts for Suzuki–Miyaura Cross-Coupling Reactions between Alkyl Halides and Aryl Boronic Esters

The development of an air-stable iron­(III)-based precatalyst for the Suzuki–Miyaura cross-coupling reaction of alkyl halides and unactivated aryl boronic esters is reported. Despite benefits to cost and toxicity, the proclivity of iron­(II)-based complexes to undergo deactivation via oxidation or hydrolysis is a limiting factor for their widespread use in cross-coupling reactions compared to palladium-based or nickel-based complexes. The new octahedral iron­(III) complex demonstrates long-term stability on the benchtop as assessed by a combination of 1H NMR spectroscopy, Mössbauer spectroscopy, and its sustained catalytic activity after exposure to air. The improved stability of the iron-based catalyst facilitates an improved protocol in which Suzuki–Miyaura cross-coupling reactions of valuable substrates can be assembled without the use of a glovebox and access a diverse scope of products similar to reactions assembled in the glovebox with iron­(II)-based catalysts.