Snapshots of Dioxygen Activation by Copper: The Structure of a 1:1 Cu/O<sub>2</sub> Adduct and Its Use in Syntheses of Asymmetric Bis(μ-oxo) Complexes
作者:Nermeen W. Aboelella、Elizabeth A. Lewis、Anne M. Reynolds、William W. Brennessel、Christopher J. Cramer、William B. Tolman
DOI:10.1021/ja027164v
日期:2002.9.1
The X-raystructure of a 1:1 Cu/O(2) adductrevealed side-on (eta(2)) O(2) coordination. Density functional calculations corroborated the structure, indicated a significant contribution of a Cu(III)-(O(2)(2-)) resonance form, and provided insights into the key bonding interactions. Reaction of a 1:1adduct supported by a slightly different beta-diketiminate ligand with Cu(I) reagents resulted in the
Selective oxidation of exogenous substrates by a bis-Cu(III) bis-oxide complex: Mechanism and scope
作者:Tao A.G. Large、Viswanath Mahadevan、William Keown、T. Daniel P. Stack
DOI:10.1016/j.ica.2018.11.027
日期:2019.2
Cu(III)(2)(mu-O)(2) bis-oxides (O) form spontaneously by direct oxygenation of nitrogen-chelated Cu(I) species and constitute a diverse class of versatile 2e(-)/2H(+) oxidants, but while these species have attracted attention as biomimetic models for dinuclear Cu enzymes, reactivity is typically limited to intramolecular ligand oxidation, and systems exhibiting synthetically useful reactivity with exogenous substrates are limited. O-TMPD (TMPD = N-1, N-1, N-3, N-3-tetramethylpropane-1,3-diamine) presents an exception, readily oxidizing a diverse array of exogenous substrates, including primary alcohols and amines selectively over their secondary counterparts in good yields. Mechanistic and DFT analyses suggest substrate oxidation proceeds through initial axial coordination, followed by rate-limiting rotation to position the substrate in the Cu(III) equatorial plane, whereupon rapid deprotonation and oxidation by net hydride transfer occurs. Together, the results suggest the selectivity and broad substrate scope unique to O-TMPD are best attributed to the combination of ligand flexibility, limited steric demands, and ligand oxidative stability. In keeping with the absence of rate-limiting C-H scission, O-TMPD exhibits a marked insensitivity to the strength of the substrate C-alpha-H bond, readily oxidizing benzyl alcohol and 1-octanol at near identical rates.