Dicopper(i,i) and delocalized mixed-valent dicopper(i,ii) complexes of a sterically hindered carboxylate ligand

Abstract

Admixture of the lithium salt of the bulky ligand 2,6-dimesitylbenzoate [ArCO₂]⁻ with [Cu(CH₃CN)₄]O₃SCF₃ yielded the dicopper(I,I) complex [(ArCO₂)₂Cu₂(THF)₂)] (1), which upon oxidation with AgX (X = SbF₆⁻ or ClO₄⁻) in THF afforded the mixed-valent complexes [(ArCO₂)₂Cu₂(THF)₂]SbF₆ (2) and [(ArCO₂)₂Cu₂(THF)₃]ClO₄ (3), respectively. Fully delocalized mixed-valent (Cu^1.5Cu^1.5) formulations for 2 and 3 were determined on the basis of X-ray crystallography and UV-vis, resonance Raman, ¹H NMR, and EPR spectroscopy. Notably, solvent dependent UV-vis spectra suggest that THF and/or counter ion coordination influence the intermetal bonding interactions in the mixed-valent cores.