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

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)(2)Cu-2(THF)(2))] (1), which upon oxidation with AgX (X = SbF6- or ClO4-) in THF afforded the mixed-valent complexes [(ArCO2)(2)Cu-2(THF)(2)]SbF6 (2) and [(ArCO2)(2)Cu-2(THF)(3)]ClO4 (3), respectively. Fully delocalized mixed-valent ((CuCu1.5)-Cu-1.5) formulations for 2 and 3 were determined on the basis of X-ray crystallography and UV-vis, resonance Raman, H-1 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.