Toward asymmetric aziridination with an iron complex supported by a D 2 -symmetric tetra-NHC.

A neutral D 2 -symmetric macrocyclic tetra-N-heterocyclic carbene ligand was synthesized. The macrocycle was ligated to iron(II) via transmetalation from an isolated silver complex that has two conformers. The iron complex catalyzed the first stereospecific aziridination between aryl azides and aliphatic alkenes, albeit with low ee's.