This work describes small molecule activation by copper and iron complexes with structurally and electronically modified bis(oxazoline) (BOX) ligand systems, focusing on dioxygen and nitric oxide as substrates. Dioxygen activation at low temperatures by copper(I) complexes with neutral BOX scaffolds generated the side on peroxo dicopper(II) systems that resemble the intermediates found in type III copper proteins, whereas those complexes with an anionic BOX-derived scaffold generated the bis(µ-oxido) dicopper(III) species. The bis(µ-oxido) system has recently been proposed as an active intermediate of pMMO. All complexes have been comprehensively characterized in solid state and solution, including single crystal X-ray crystallographic structure determination for representative examples, and the intermediates were screened for substrate reactivity. Moreover, triggered by protonation/deprotonation reactions, it was possible to interconvert the side-on peroxo dicopper(II) and bis(µ-oxido) dicopper(III) systems. The reaction of iron(II) BOX complexes with nitric oxide successfully generated a dinitrosyl iron complex that was isolated and characterized as well. In conclusion, BOX ligands that have been termed as a privileged ligand class in the field of asymmetric catalysis, have proved themselves to be useful in the field of bioinorganic chemistry as well.
Keywords: small molecule activation; type III copper proteins; side-on peroxo dicopper(II); bis mu-oxido dicopper(III); nitric oxide; dinitrosyl iron complex; bis(oxazoline)
