Crystal structure and dynamic properties of a bimetallic cyano complex Cd(C4H8O2)Cu(CN)3 with an interpenetrating 3D framework containing a 1,4-dioxane bridging ligand as a rotor

Abstract

The title complex Cd(C₄H₈O₂)Cu(CN)₃ has a 3D twofold interpenetrating framework structure. The structural base of the framework is a planar hexagonal network complex of [Cu(CN)₃Cd]_∞ ,which is formed with cyanides connecting the coordination sites of Cu(I) ions with a triangle planar form and the equatorial coordination sites of Cd(II) ions with a trigonal bipyramid form. The networks are stacked and a 1,4-dioxane molecule coordinates to two Cd(II) ions in alternate networks as a bridging ligand. The 1,4-dioxane ligand penetrates a hexagonal window of the network sandwiched between the bridged networks. This 1,4-dioxane bridge completes the 3D twofold interpenetrating framework structure. ²H-NMR powder patterns of the deuterated complex Cd(C₄D₈O₂)Cu(CN)₃ revealed the dynamics of the 1,4-dioxane bridge as a rotor. Above 253 K, the 1,4-dioxane ligand undergoes rotational motion combined with a ring inversion between two chair conformations. The free energy of activation ΔG^‡ for the ring inversion was calculated to be 41.4(7) kJ mol⁻¹ at 298 K.