Reactions of Terminal Olefins With Iron Carbenes

Abstract

ABSTRACT The application of sustainable, earth‐abundant iron complexes to the olefin metathesis of terminal olefins remains a formidable challenge due to competitive, metathesis‐divergent deactivation pathways. Herein, we investigate the reactivity of pincer‐supported iron carbenes toward various terminal olefins. Reactions with styrene, ethylene, or 2‐vinylanisole under ambient conditions proceed through 2π + 2π cycloadditions to generate transient metallacyclobutane intermediates that rapidly undergo metathesis‐divergent β‐hydride elimination to yield stable iron allyl hydride complexes. The addition of benzonitrile to the iron allyl hydride complexes demonstrates a unique hydride transfer from the iron center to the nitrile carbon, yielding a paramagnetic terminal imide complex. Conversely, reactions with the sterically demanding 1,1‐disubstituted olefin α‐methylstyrene successfully suppress β‐hydride elimination. Heating this mixture induces a 2π + 2π cycloaddition followed by cycloreversion and a subsequent 1,2‐hydride shift, resulting in productive, albeit low‐yield, metathesis to generate a paramagnetic side‐bound iron olefin complex.