title: Kinetic insights into the reactivity of the intermediates generated from hydrogen peroxide and diiron(III) complex with tris(picolyl)amine (TPA).
abstract: Two intermediates (2 and 3) are formed consecutively in the reaction of a diiron(III) complex [Fe(III)(2)(μ-O)(OH)(H(2)O)(TPA)(2)](ClO(4))(3) (TPA = tris(2-pyridylmethyl)amine, tris(picolyl)amine) with H(2)O(2) in CH(3)CN at -40 °C. Low-temperature stopped-flow studies showed that both species are kinetically competent in oxidation of phosphines and phenols. The first intermediate (2) reacts with substrates very rapidly (second-order rate constants reach 10(5)-10(6) M(-1) s(-1) for substituted triarylphosphines and 10(3)-10(5) M(-1) s(-1) for substituted phenols), in keeping with a diiron(IV)-oxo formulation. The second intermediate (3), a mixed-valent Fe(III)Fe(IV) species, is more stable than 2, and reacts with substrates more slowly (second-order rate constants range from 150 to 550 M(-1) s(-1) for triaryl phosphine oxidation, and from 18 to 790 M(-1) s(-1) for phenol oxidation). Reaction rates increase with increasing electron donating abilities of substituents, indicating that both 2 and 3 act as electrophilic oxidants.
authors: Department of Chemistry, Tufts University, Medford, MA, USA. Xianru.Sun@tufts.edu
authors: Xianru
authors: X
authors: Sun
authors: Sergiy V
authors: SV
authors: Kryatov
authors: Elena V
authors: EV
authors: Rybak-Akimova
mesh_terms: D056831:Coordination Complexes / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry*; D007700:Kinetics; D010084:Oxidation-Reduction; D019800:Phenol / Q000737:chemistry; D010720:Phosphines / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D005290:Ferric Compounds; D010720:Phosphines; D011725:Pyridines; C431843:tris(2-pyridylmethyl)amine; D019800:Phenol; D006861:Hydrogen Peroxide; C044646:phosphine