Ene Reactivity of an FeNR Bond Enables the Catalytic α‑Deuteration of Nitriles and Alkynes

Herein, we report the reactions of an Fe(II) imido complex [Ph₂B(^tBuIm)₂FeNDipp]⁻ (1) with internal alkynes and isobutyronitrile, affording the Fe amido allenyl complexes [Ph₂B(^tBuIm)₂Fe(NHDipp)((R₁)CCC(R₂)(H))]⁻ (R₁ = Et or ⁿPr; R₂ = Me or Et, 2–5) and the Fe amido keteniminate complex [Ph₂B(^tBuIm)₂Fe(NHDipp)(NCCMe₂)K(THF)]_n (8-K), respectively. These transformations represent the previously unknown ene-like reactivity of a metal–ligand multiple bond. Stoichiometric reactions of 2 and 8-K with DippNH₂ lead to the regeneration of 3-hexyne and isobutyronitrile, respectively, with concomitant formation of the bis(anilido) complex [Ph₂B(^tBuIm)₂Fe(NHDipp)₂]⁻ (9). These results provide the platform for 1 as an efficient catalyst for the selective α-deuteration of nitriles and alkynes by RND₂. These results demonstrate a new reaction mode for metal imido complexes and suggest new avenues for using the imido ligand in catalysis.