An Oxido‐Bridged Diiron(II) Complex as Functional Model of Catechol Dioxygenase

Abstract An oxido‐bridged diiron(II)‐phenanthroline complex, [Fe 2 O(phen) 2 Cl 2 ] ( 1 ) [phen =1,10‐phenanthroline] has been synthesized from an oxido‐bridged diiron(III) precursor in presence of sodium azide and structurally characterized by different spectroscopic tools including single crystal X‐ray diffraction study.From X‐ray crystal structure of 1 , it is revealed that each of the Fe(II) centre is in distorted octahedral geometry with FeN 4 OCl core and the molecule crystallizes in P nc2 space group. Bond valence sum (BVS) calculation confirms the existence of iron ions in +2 oxidation state in 1 . The diiron(II) complex has been evaluated as model system for the catechol dioxygenase enzyme by using 3,5 ‐ di‐ tert ‐butylcatechol (DTBC) as the substrate in acetonitrile medium, revealing that 1 efficiently mimics the catalytic cycle of catechol dioxygenase. Upon stoichiometric addition of DTBC pretreated with two equivalents of triethylamine (Et 3 N) to the diiron complex, two catecholate‐to‐iron(III) LMCT bands (515 nm and 734 nm) are observed. The in situgenerated catecholate adduct from 1 in acetonitrile solution react with dioxygen to afford exclusively extradiol cleavage products along with a small amount of benzoquinone, which is also discerned from the appearance and decrease in intensity of the electronic spectral bands around (708 nm; 507 nm) nm. Nucleophilic attack by molecular oxygen on catecholate adduct in solution provides substantial evidence for the regioselective extradiol cleavage products.