The Effect of <i>trans</i> Axial Isocyanide Ligands on Iron(II) Tetra‐NHC Complexes and their Reactivity in Olefin Epoxidation

The performance of trans axially substituted mono-(2 a) and bis(tert-butylisocyanide) (2 b) complexes derived from the highly active bio-inspired iron(II) (pre- )catalyst 2 containing an equatorial macrocyclic tetra N-heterocyclic carbene in homogenous olefin epoxidation catalysis is reported. H2O2 used as oxidant combination with Lewis acid Sc(OTf)3 additive resulting a considerable improvement catalytic activity. In contrast to other iron catalysts, introduction π-accepting isocyanide ligands does not improve b posed by cyclic voltammetry. However, besides their lower activity, high temperature tolerance both compounds found unique feature for NHC catalysts.