Catalytic Azoarene Synthesis from Aryl Azides Enabled by a Dinuclear Ni Complex

Azoarenes are valuable
chromophores that have been extensively
incorporated as photoswitchable elements in molecular machines and
biologically active compounds. Here, we report a catalytic nitrene
dimerization reaction that provides access to structurally and electronically
diverse azoarenes. The reaction utilizes aryl azides as nitrene precursors
and generates only gaseous N2 as a byproduct. By circumventing
the use of a stoichiometric redox reagent, a broad range of organic
functional groups are tolerated, and common byproducts of current
methods are avoided. A catalyst featuring a NiNi bond is found
to be uniquely effective relative to those containing only a single
Ni center. The mechanistic origins of this nuclearity effect are described.