Carbon–Hydrogen Bond Activation, C–N Bond Coupling, and Cycloaddition Reactivity of a Three-Coordinate Nickel Complex Featuring a Terminal Imido Ligand

The three-coordinate imidos (dtbpe)­NiNR (dtbpe = <sup><i>t</i></sup>Bu<sub>2</sub>PCH<sub>2</sub>CH<sub>2</sub>P<sup><i>t</i></sup>Bu<sub>2,</sub> R = 2,6-<sup><i>i</i></sup>Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub>, 2,4,6-Me<sub>3</sub>C<sub>6</sub>H<sub>2</sub> (Mes), and 1-adamantyl (Ad)), which contain a legitimate Ni–N double bond as well as basic imido nitrogen based on theoretical analysis, readily deprotonate HCCPh to form the amide acetylide species (dtbpe)­Ni­{NH­(Ar)}­(CCPh). In the case of R = 2,6-<sup><i>i</i></sup>Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub>, reductive carbonylation results in formation of the (dtbpe)­Ni­(CO)<sub>2</sub> along with the N–C coupled product keteneimine PhCHCN­(2,6- <sup><i>i</i></sup>Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub>). Given the ability of the NiN bond to have biradical character as suggested by theoretical analysis, H atom abstraction can also occur in (dtbpe)­NiN­{2,6-<sup><i>i</i></sup>Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub>} when this species is treated with HSn­(<sup><i>n</i></sup>Bu)<sub>3</sub>. Likewise, the microscopic reverse reactionconversion of the Ni­(I) anilide (dtbpe)­Ni­{NH­(2,6-<sup><i>i</i></sup>Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)} to the imido (dtbpe)­NiN­{2,6-<sup><i>i</i></sup>Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub>}is promoted when using the radical Mes*O<sup>•</sup> (Mes* = 2,4,6-<sup><i>t</i></sup>Bu<sub>3</sub>C<sub>6</sub>H<sub>2</sub>). Reactivity studies involving the imido complexes, in particular (dtbpe)­NiN­{2,6-<sup><i>i</i></sup>Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub>}, are also reported with small, unsaturated molecules such as diphenylketene, benzylisocyanate, benzaldehyde, and carbon dioxide, including the formation of C–N and N–N bonds by coupling reactions. In addition to NMR spectroscopic data and combustion analysis, we also report structural studies for all the cycloaddition reactions involving the imido (dtbpe)­NiN­{2,6-<sup><i>i</i></sup>Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub>}.