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Ligand Macrocycle Structural Effects on Copper−Dioxygen Reactivity

Lam, Bernice M. T ; Halfen, Jason A ; Young, Victor G ; Hagadorn, John R ; Holland, Patrick L ; Lledós, Agustí ; Cucurull-Sánchez, Lourdes ; Novoa, Juan J ; Alvarez, Santiago ; Tolman, William B

Inorganic chemistry, 2000-09, Vol.39 (18), p.4059-4072 [Periódico revisado por pares]

United States: American Chemical Society

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  • Título:
    Ligand Macrocycle Structural Effects on Copper−Dioxygen Reactivity
  • Autor: Lam, Bernice M. T ; Halfen, Jason A ; Young, Victor G ; Hagadorn, John R ; Holland, Patrick L ; Lledós, Agustí ; Cucurull-Sánchez, Lourdes ; Novoa, Juan J ; Alvarez, Santiago ; Tolman, William B
  • Assuntos: Copper - chemistry ; Electrochemistry ; Ligands ; Models, Molecular ; Molecular Structure ; Oxygen - chemistry
  • É parte de: Inorganic chemistry, 2000-09, Vol.39 (18), p.4059-4072
  • Notas: istex:F7BDAF69FFB04A6BAE47711A027A3A5E64382284
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  • Descrição: With the goal of understanding how the nature of the tridentate macrocyclic supporting ligand influences the relative stability of isomeric μ-η2:η2-peroxo- and bis(μ-oxo)dicopper complexes, a comparative study was undertaken of the O2 reactivity of Cu(I) compounds supported by the 10- and 12-membered macrocycles, 1,4,7-R3-1,4,7-triazacyclodecane (R3TACD; R = Me, Bn, iPr) and 1,5,9-triisopropyl-1,5,9-triazacyclododecane (iPr3TACDD). While the 3-coordinate complex [(iPr3TACDD)Cu]SbF6 was unreactive with O2, oxygenation of [(R3TACD)Cu(CH3CN)]X (R = Me or Bn; X = ClO4 - or SbF6 -) at −80 °C yielded bis(μ-oxo) species [(R3TACD)2Cu2(μ-O)2]X2 as revealed by UV−vis and resonance Raman spectroscopy. Interestingly, unlike the previously reported system supported by 1,4,7-triisopropyl-1,4,7-triazacyclononane (iPr3TACN), which yielded interconverting mixtures of peroxo and bis(μ-oxo) compounds (Cahoy, J.; Holland, P. L.; Tolman, W. B. Inorg. Chem. 1999, 38, 2161), low-temperature oxygenation of [(iPr3TACD)Cu(CH3CN)]SbF6 in a variety of solvents cleanly yielded a μ-η2:η2-peroxo product, with no trace of the bis(μ-oxo) isomer. The peroxo complex was characterized by UV−vis and resonance Raman spectroscopy, as well as an X-ray crystal structure (albeit of marginal quality due to disorder problems). Intramolecular attack at the α C−H bonds of the substituents was indicated as the primary decomposition pathway of the oxygenated compounds through examination of the decay kinetics and the reaction products, which included bis(μ-hydroxo)− and μ-carbonato−dicopper complexes that were characterized by X-ray diffraction. A rationale for the varying results of the oxygenation reactions was provided by analysis of (a) the X-ray crystal structures and electrochemical behavior of the Cu(I) precursors and (b) the results of theoretical calculations of the complete oxygenated complexes, including all ligand atoms, using combined quantum chemical/molecular mechanics (integrated molecular orbital molecular mechanics, IMOMM) methods. The size of the ligand substituents was shown to be a key factor in controlling the relative stabilities of the peroxo and bis(μ-oxo) forms, and the nature of this influence was shown by both theory and experiment to depend on the ligand macrocycle ring size.
  • Editor: United States: American Chemical Society
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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