Tuning of the Copper鈥揟hioether Bond in Tetradentate N3S(thioether) Ligands; O鈥揙 Bond Reductive Cleavage via a [CuII2(渭-1,2-peroxo)]2+/[CuIII

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• 作者：Sunghee Kim ; Jake W. Ginsbach ; A. Imtiaz Billah ; Maxime A. Siegler ; Cathy D. Moore ; Edward I. Solomon ; Kenneth D. Karlin
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：June 4, 2014
• 年：2014
• 卷：136
• 期：22
• 页码：8063-8071
• 全文大小：556K
• 年卷期：v.136,no.22(June 4, 2014)
• ISSN：1520-5126

文摘

Current interest in copper/dioxygen reactivity includes the influence of thioether sulfur ligation, as it concerns the formation, structures, and properties of derived copper-dioxygen complexes. Here, we report on the chemistry of {L-Cu^I}₂-(O₂) species L = ^DMMESE, ^DMMESP, and ^DMMESDP, which are N₃S_(thioether)-based ligands varied in the nature of a substituent on the S atom, along with a related N₃O_(ether) (EOE) ligand. Cu^I and Cu^II complexes have been synthesized and crystallographically characterized. Copper(I) complexes are dimeric in the solid state, [{L-Cu^I}₂](B(C₆F₅)₄)₂, however are shown by diffusion-ordered NMR spectroscopy to be mononuclear in solution. Copper(II) complexes with a general formulation [L-Cu^II(X)]ⁿ⁺ {X = ClO₄^{鈥?/sup>, n = 1, or X = H₂O, n = 2} exhibit distorted square pyramidal coordination geometries and progressively weaker axial thioether ligation across the series. Oxygenation (鈭?30 掳C) of {(DMMESE)CuI}+ results in the formation of a trans-渭-1,2-peroxodicopper(II) species [{(DMMESE)CuII}₂(渭-1,2-O₂2鈥?/sup>)]2+ (1P). Weakening the Cu鈥揝 bond via a change to the thioether donor found in DMMESP leads to the initial formation of [{(DMMESP)CuII}₂(渭-1,2-O₂2鈥?/sup>)]2+ (2P) that subsequently isomerizes to a bis-渭-oxodicopper(III) complex, [{(DMMESP)CuIII}₂(渭-O2鈥?/sup>)₂]2+ (2O), with 2P and 2O in equilibrium (K_eq = [2O]/[2P] = 2.6 at 鈭?30 掳C). Formulations for these Cu/O₂ adducts were confirmed by resonance Raman (rR) spectroscopy. This solution mixture is sensitive to the addition of methylsulfonate, which shifts the equilibrium toward the bis-渭-oxo isomer. Further weakening of the Cu鈥揝 bond in DMMESDP or substitution with an ether donor in DMMEOE leads to only a bis-渭-oxo species (3O and 4O, respectively). Reactivity studies indicate that the bis-渭-oxodicopper(III) species (2O, 3O) and not the trans-peroxo isomers (1P and 2P) are responsible for the observed ligand sulfoxidation. Our findings concerning the existence of the 2P/2O equilibrium contrast with previously established ligand-CuI/O₂ reactivity and possible implications are discussed.}