Ene Reactivity of an Fe═NR Bond Enables the Catalytic α-Deuteration of Nitriles and Alkynes.

Abstract

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.