title: Dioxygen reactivity of biomimetic iron-catecholate and iron-o-aminophenolate complexes of a tris(2-pyridylthio)methanido ligand: aromatic C-C bond cleavage of catecholate versus o-iminobenzosemiquinonate radical formation.
abstract: An iron(III)-catecholate complex [L(1)Fe(III)(DBC)] (2) and an iron(II)-o-aminophenolate complex [L(1)Fe(II)(HAP)] (3; where L(1) = tris(2-pyridylthio)methanido anion, DBC = dianionic 3,5-di-tert-butylcatecholate, and HAP = monoanionic 4,6-di-tert-butyl-2-aminophenolate) have been synthesised from an iron(II)-acetonitrile complex [L(1)Fe(II)(CH(3)CN)(2)](ClO(4)) (1). Complex 2 reacts with dioxygen to oxidatively cleave the aromatic C-C bond of DBC giving rise to selective extradiol cleavage products. Controlled chemical or electrochemical oxidation of 2, on the other hand, forms an iron(III)-semiquinone radical complex [L(1)Fe(III)(SQ)](PF(6)) (2(ox)-PF(6); SQ = 3,5-di-tert-butylsemiquinonate). The iron(II)-o-aminophenolate complex (3) reacts with dioxygen to afford an iron(III)-o-iminosemiquinonato radical complex [L(1)Fe(III)(ISQ)](ClO(4))(3(ox)-ClO(4); ISQ = 4,6-di-tert-butyl-o-iminobenzosemiquinonato radical) via an iron(III)-o-amidophenolate intermediate species. Structural characterisations of 1, 2, 2(ox) and 3(ox) reveal the presence of a strong iron-carbon bonding interaction in all the complexes. The bond parameters of 2(ox) and 3(ox) clearly establish the radical nature of catecholate- and o-aminophenolate-derived ligand, respectively. The effect of iron-carbon bonding interaction on the dioxygen reactivity of biomimetic iron-catecholate and iron-o-aminophenolate complexes is discussed.
authors: Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India.
authors: Partha
authors: P
authors: Halder
authors: Sayantan
authors: S
authors: Paria
authors: Tapan Kanti
authors: TK
authors: Paine
mesh_terms: D000627:Aminophenols / Q000737:chemistry; D016227:Benzoquinones / Q000138:chemical synthesis / Q000737:chemistry; D032701:Biomimetics; D002396:Catechols / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D010100:Oxygen / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*
chemical_list: D000627:Aminophenols; D016227:Benzoquinones; D002396:Catechols; D005290:Ferric Compounds; D005296:Ferrous Compounds; D008024:Ligands; D011725:Pyridines; C025232:semiquinone radicals; C029347:2-thiopyridine; D010100:Oxygen