Microporous dinuclear copper(II) trans-1,4-cyclohexanedicarboxylate: heterogeneous oxidation catalysis with hydrogen peroxide and X-ray powder structure of peroxo copper(II) intermediate

A two-dimensional microporous dinuclear copper(II) trans-1,4-cyclohexanedicarboxylate, [CuII,II2(OOCC6H10COO)2] ⋅ H2O (1), can act as a heterogeneous catalyst for selective oxidations of various alcohols with hydrogen peroxide. Complex 1 catalyzed the selective oxidations of 2-propanol, cyclohexanol, benzyl alcohol, 2-octanol, and 1-octanol with >99% selectivities in a heterogeneous system. A green-colored active intermediate, H2[CuII,II2(OOCC6H10COO)2(O2)] ⋅ H2O (2), observed in the reaction of 1 with a 20-fold excess H2O2 in acetonitrile was characterized by elemental analysis, TG/DTA, magnetic susceptibility, FT-IR, diffuse reflectance UV-vis, EPR, X-ray powder diffraction (XRPD), resonance Raman spectra, BET surface area, pore size distribution, and nitrogen occlusion measurements. The molecular structure of 2 was determined from XRPD data and refined by the Rietveld method. The microporous structure of 2 was constructed by intramolecular bridging of μ-1,2-trans CuOOCu species between two-dimensional [Cu2(O2CC6H10CO2)] layers. The complex 2 was the first example of the microporous copper(II) peroxo complex for heterogeneous oxidation catalysis.