Ene Reactivity of an Fe=NR Bond Enables the Catalytic a-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 alpha-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.

Automated summary

In this study, we report the previously unknown reactions of an Fe(II) imido complex with internal alkynes and isobutyronitrile, resulting in the formation of novel Fe amido allenyl and keteniminate complexes. Compound 1, as a catalyst, exhibits efficient selective α-deuteration of nitriles and alkynes. These findings reveal a new reactivity mode for metal imido complexes and provide new insights into the use of imido ligands in catalysis.