title: Dramatic influence of an anionic donor on the oxygen-atom transfer reactivity of a Mn(V) -oxo complex.
abstract: Addition of an anionic donor to an Mn(V) (O) porphyrinoid complex causes a dramatic increase in 2-electron oxygen-atom-transfer (OAT) chemistry. The 6-coordinate [Mn(V) (O)(TBP8 Cz)(CN)](-) was generated from addition of Bu4 N(+) CN(-) to the 5-coordinate Mn(V) (O) precursor. The cyanide-ligated complex was characterized for the first time by Mn K-edge X-ray absorption spectroscopy (XAS) and gives MnO=1.53 Å, MnCN=2.21 Å. In combination with computational studies these distances were shown to correlate with a singlet ground state. Reaction of the CN(-) complex with thioethers results in OAT to give the corresponding sulfoxide and a 2e(-) -reduced Mn(III) (CN)(-) complex. Kinetic measurements reveal a dramatic rate enhancement for OAT of approximately 24 000-fold versus the same reaction for the parent 5-coordinate complex. An Eyring analysis gives ΔH(≠) =14 kcal mol(-1) , ΔS(≠) =-10 cal mol(-1)  K(-1) . Computational studies fully support the structures, spin states, and relative reactivity of the 5- and 6-coordinate Mn(V) (O) complexes.
authors.affiliation: Department of Chemistry, The Johns Hopkins University, Baltimore, MD (USA).
authors.forename: Heather M
authors.initials: HM
authors.lastname: Neu
authors.forename: Matthew G
authors.initials: MG
authors.lastname: Quesne
authors.forename: Tzuhsiung
authors.initials: T
authors.lastname: Yang
authors.forename: Katharine A
authors.initials: KA
authors.lastname: Prokop-Prigge
authors.forename: Kyle M
authors.initials: KM
authors.lastname: Lancaster
authors.forename: James
authors.initials: J
authors.lastname: Donohoe
authors.forename: Serena
authors.initials: S
authors.lastname: DeBeer
authors.forename: Sam P
authors.initials: SP
authors.lastname: de Visser
authors.forename: David P
authors.initials: DP
authors.lastname: Goldberg
mesh_terms: D000838:Anions / Q000737:chemistry; D056831:Coordination Complexes / Q000737:chemistry*; D008345:Manganese / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*
chemical_list: D000838:Anions; D056831:Coordination Complexes; D008345:Manganese; D010100:Oxygen
keywords: manganese; oxygen-atom-transfer; porphyrinoids; spin state reactivity; sulfoxidation