Intramolecular C-H Functionalization Followed by a [2 + 2] Addition via an Intermediate Nickel-Nitridyl Complex.

Irradiation of a disphenoidal Ni(II) azido complex, [Cz (Pyr )NiN] (1), revealed an unprecedented nickel complex, [Cz (Pyr )(NH-Pyr )] (2), in >90% isolated yield. As evidenced by single-crystal X-ray diffraction, 2 is produced by double intramolecular C-H activation of a putative nickel-nitridyl intermediate, [Cz (Pyr )Ni-⃛N]. Calculations support the generation of an intermediate with significant nitridyl radical character after the loss of N, which, in turn, undergoes tandem C-H activations, leading to functionalized intermediates and products. This is an unprecedented example of transient Ni-⃛N-promoted intramolecular C-H functionalization, followed by a [2 + 2] addition, yielding bis-metallacyclic product 2. Complex 2 is also observed from the reaction of Ni(I) precursor Cz (Pyr )Ni (3) and MeSiN, suggesting a unique thermal route toward a masked nickel-nitridyl intermediate.