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].