Structural properties of [Cu(ii)3L6] cages: bridged polyatomic anion effects on unprecedented efficiency of heterogeneous catechol oxidation

Abstract

Self-assembly of CuX₂ (X⁻ = BF₄⁻, ClO₄⁻, PF₆⁻, and SbF₆⁻) with a bidentate ethylmethylbis(3-pyridine)silane ligand (L) in the presence of additional polyatomic anions (X′ = SiF₆²⁻ and PF₆⁻) gives rise to single crystals consisting of the X′@[Cu(II)₃L₆] cage motif. These cages exist as discrete or anion-bridged 3D networks depending on outside anions. The anion-bridged 3D networks interpenetrate in a four-fold fashion, and show, to our best knowledge, the most effective heterogeneous catalysis in 3,5-di-tert-butylcatechol oxidation reaction within 20 min at room temperature. Surprisingly, the heterogeneous catalysis is more effective than its corresponding homogeneous catalysis. Such notable catalytic effects can be explained by the maintenance of 3D inter-cage Cu⋯Cu distance as a catalytic center.