1610044-26-2Relevant academic research and scientific papers
Tuning of the copper-thioether bond in tetradentate N3S (thioether) ligands; O-O bond reductive cleavage via a [Cu II2(μ-1,2-peroxo)]2+/[CuIII 2(μ-oxo)2]2+ equilibrium
Kim, Sunghee,Ginsbach, Jake W.,Billah, A. Imtiaz,Siegler, Maxime A.,Moore, Cathy D.,Solomon, Edward I.,Karlin, Kenneth D.
, p. 8063 - 8071 (2014/06/23)
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-CuI}2-(O2) species L = DMMESE, DMMESP, and DMMESDP, which are N 3S(thioether)-based ligands varied in the nature of a substituent on the S atom, along with a related N3O(ether) (EOE) ligand. CuI and CuII complexes have been synthesized and crystallographically characterized. Copper(I) complexes are dimeric in the solid state, [{L-CuI}2](B(C 6F5)4)2, however are shown by diffusion-ordered NMR spectroscopy to be mononuclear in solution. Copper(II) complexes with a general formulation [L-CuII(X)]n+ {X = ClO4-, n = 1, or X = H2O, n = 2} exhibit distorted square pyramidal coordination geometries and progressively weaker axial thioether ligation across the series. Oxygenation (-130 °C) of {( DMMESE)CuI}+ results in the formation of a trans-μ-1,2-peroxodicopper(II) species [{(DMMESE)Cu II}2(μ-1,2-O22-)]2+ (1P). Weakening the Cu-S bond via a change to the thioether donor found in DMMESP leads to the initial formation of [{( DMMESP)CuII}2(μ-1,2-O2 2-)]2+ (2P) that subsequently isomerizes to a bis-μ-oxodicopper(III) complex, [{(DMMESP)CuIII} 2(μ-O2-)2]2+ (2O), with 2P and 2O in equilibrium (Keq = [2 O]/[2P] = 2.6 at -130 °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-μ-oxo isomer. Further weakening of the Cu-S bond in DMMESDP or substitution with an ether donor in DMMEOE leads to only a bis-μ-oxo species (3O and 4 O, respectively). Reactivity studies indicate that the bis-μ-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.
