Stable N-heterocyclic carbene derivatives of copper(i) and silver(i) containing radical anion redox active ligands

N-Heterocyclic carbene is a versatile ligand for the preparation of copper(i) and silver(i) derivatives bearing the radical anion forms of redox active o-benzoquinone and o-iminobenzoquinone. The paramagnetic three-coordinated copper(i) and silver(i) o-benzosemiquinone and o-iminobenzosemiquinone complexes were prepared and characterized by EPR spectroscopy and X-ray diffraction analysis.