117371-33-2Relevant academic research and scientific papers
Three-coordinate copper(II)-phenolate complexes
Jazdzewski,Holland,Pink,Young Jr.,Spencer,Tolman
, p. 6097 - 6107 (2001)
The reactions of LCuCl (L = 2,4-bis((2,6-diisopropylphenyl)imido)pentane (LiPr), 2,4-bis((2,6-diisopropylphenyl)-imido)-3-chloropentane (LCliPr)) with the phenolates T1OAr (Ar = C6H3Me2, C6H4Me, C6H4tBu) and NaOC6H3(tBu)2 were explored. Novel three-coordinate CU(II) -phenolates, LCuOAr, were isolated from the reactions with the thallium phenolates and were characterized by X-ray crystallography and spectroscopy (UV-vis, EPR). The complexes feature short Cu-O(phenolate) distances (average Cu-O = 1.81 A) and, with one exception, irregular N-Cu-O(phenolate) angles that differ within each compound (15° 1-Cu-O-∠N2-Cu-O). The exception is LiPrCu(OC6H4tBu), for which X-ray structures at -100 and 25 °C differed due to an unusual reversible phase change with nonmerohedral twinning (2:1 ratio) in the low-temperature form. The high-temperature form has local C2ν symmetry (Δ = 0°), and upon cooling below the phase transition temperature (-8 ± 5 °C) lateral movement of the phenolate ligand (Δ = 17.6°) and rotation of the phenolate plane by 10.7° occurs. Resonance Raman spectroscopic data acquired for LiPrCu(OC6H4tBu) corroborated assignment of phenolate → Cu(II) LMCT character in the UV-vis spectra. Cyclic voltammetry experiments (THF, 0.5 M NBu4PF6) revealed negative E1/2 values for the Cu(II)/Cu(I) couples relative to NHE, consistent with enhanced stabilization of the Cu(II) state by both the strongly electron donating β-diketiminate ligand and the phenolates. Although thermally stable, the Cu(II)-phenolates are unusually reactive with dioxygen, albeit to give product(s) that have yet to be identified. In the reaction of LiPrCuCl with NaOC6H3(tBu)2 no Cu(II)-phenolate was observed. Instead, a Cu(I) complex was generated quantitatively by trapping with added isocyanide, [LiPrCuNC(C6H3Me2)], along with 3,3′,5,5′-tetra-tert-butyl-4,4′-dibenzoquinone and 2,6-di-tert-butylphenol in 27 ± 3% and 46 ± 6% yields, respectively, corresponding to the overall reaction 4LiPrCu11Cl + 4NaOAr → 4LiPrCu(I) + 4NaCl + dibenzoquinone + 2(phenol).
