title: A Peroxynitrite Dicopper Complex: Formation via Cu-NO and Cu-O2Intermediates and Reactivity via O-O Cleavage Chemistry.
abstract: A mixed-valent Cu(I)Cu(II) complex, [CuI,II2(UN-O-)]2+(1), reacts with NO(g)at -80 °C to form [CuI,II2(UN-O-)(NO)]2+(2), best described as a mixed-valent nitrosyl complex that has a ν(N-O) band at 1670 cm-1in its infrared (IR) spectrum. Complex 2 undertakes a one-electron oxidation via the addition of O2(g)to generate a new intermediate, best described as a superoxide and nitrosyl adduct, [CuII2(UN-O-)(NO)(O2-)]2+(3), based on its distinctively blue-shifted ν(N-O) band at 1853 cm-1. Over the course of 20 min at -80 °C, 3 is converted to the peroxynitrite (PN) complex [CuII2(UN-O-)(-OON═O)]2+(4), which was characterized by low-temperature electrospray ionization mass spectrometry (ESI-MS) and IR spectroscopy; ν(N-O) absorptions at 1520 and 1640 cm-1have been assigned as cis- and trans-conformers of the PN ligand in 4. Alternatively, the superoxide complex [CuII2(UN-O-)(O2•-)]2+(5) is found to react with NO(g)to generate the same intermediate superoxide and nitrosyl adduct 3 (based on IR criteria), which likewise converts to the same PN complex 4. The O-O bond in 4 undergoes heterolysis in dichloromethane solvent and is postulated to produce nitronium ion, leading to ortho-nitration of 2,4-di-tert-butylphenol (DTBP). However, in 2-methyltetrahydrofuran as solvent, the O-O bond undergoes homolysis to generate•NO2(detected spectrophotometrically) and a putative higher-valent complex, [CuII,III2(UN-O-)(O2-)]2+, that abstracts a H-atom from DTBP to give [CuII2(UN-O-)(OH)]2+and a phenoxyl radical. The latter may dimerize to form the bis-phenol observed experimentally or couple with the•NO2present, leading to o-phenol nitration.
authors.affiliation: Department of Chemistry, Johns Hopkins University , Baltimore, Maryland 21218, United States.
authors.forename: Rui
authors.initials: R
authors.lastname: Cao
authors.affiliation: Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States.
authors.forename: Lee Taylor
authors.initials: LT
authors.lastname: Elrod
authors.affiliation: Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States.
authors.forename: Ryan L
authors.initials: RL
authors.lastname: Lehane
authors.affiliation: Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States.
authors.forename: Eunsuk
authors.initials: E
authors.lastname: Kim
authors.affiliation: Department of Chemistry, Johns Hopkins University , Baltimore, Maryland 21218, United States.
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Karlin
mesh_terms: D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry; D003300:Copper / Q000737:chemistry*; D015394:Molecular Structure; D009569:Nitric Oxide / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D030421:Peroxynitrous Acid / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D030421:Peroxynitrous Acid; D009569:Nitric Oxide; D003300:Copper; D010100:Oxygen