title: Characterization and reactivity of a terminal nickel(III)-oxygen adduct.
abstract: High-valent terminal metal-oxygen adducts are hypothesized to be the potent oxidizing reactants in late transition metal oxidation catalysis. In particular, examples of high-valent terminal nickel-oxygen adducts are scarce, meaning there is a dearth in the understanding of such oxidants. A monoanionic Ni(II)-bicarbonate complex has been found to react in a 1:1 ratio with the one-electron oxidant tris(4-bromophenyl)ammoniumyl hexachloroantimonate, yielding a thermally unstable intermediate in high yield (ca. 95%). Electronic absorption, electronic paramagnetic resonance, and X-ray absorption spectroscopies and density functional theory calculations confirm its description as a low-spin (S = 1/2), square planar Ni(III)-oxygen adduct. This rare example of a high-valent terminal nickel-oxygen complex performs oxidations of organic substrates, including 2,6-di-tert-butylphenol and triphenylphosphine, which are indicative of hydrogen atom abstraction and oxygen atom transfer reactivity, respectively.
authors.affiliation: School of Chemistry and CRANN/AMBER Nanoscience Institute, The University of Dublin, Trinity College, College Green, Dublin 2 (Ireland).
authors.forename: Paolo
authors.initials: P
authors.lastname: Pirovano
authors.forename: Erik R
authors.initials: ER
authors.lastname: Farquhar
authors.forename: Marcel
authors.initials: M
authors.lastname: Swart
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Fitzpatrick
authors.forename: Grace G
authors.initials: GG
authors.lastname: Morgan
authors.forename: Aidan R
authors.initials: AR
authors.lastname: McDonald
mesh_terms: D000965:Antimony / Q000737:chemistry*; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D009942:Organometallic Compounds; D010636:Phenols; D000644:Quaternary Ammonium Compounds; C079938:tris(4-bromophenyl)ammoniumyl hexachloroantimonate; C035407:2,6-di-tert-butylphenol; D009532:Nickel; D000965:Antimony; D010100:Oxygen
keywords: high-valent metals; metal-oxo species; nickel; oxidation catalysis; reactive intermediates