Geometric control of cage architecture; observation of ligand-selective behaviour in the structures of [{As2(NCy)4}2M4] (M = Na, Cu; Cy = C6H11)

Abstract

The structure of [{As2(NCy)4}2Cu4] reveals a dramatic change in the metal coordination mode compared to that found in the Sb analogue [{Sb2(NCy)4}2Cu4], resulting in the distortion of the Cu4 core from a square-planar to a butterfly shape and providing the first illustration of ligand-selective cage modification in such heterobimetallic species; in contrast the square-planar Na4 arrangement found in [{Sb2(NCy)4}2M4] (M = Na, Cu, Ag) is retained in [{As2(NCy)4}2Na4].