Assemblies of Alkaline‐Earth‐Metal Ions with o ‐Tetramethyl‐Substituted Cucurbituril in the Presence of the Cadmium Tetrachloride Anion

o ‐Tetramethyl‐substituted cucurbituril ( o ‐TMeQ[6]), a polydentate ligand, has been synthesized and isolated in a controlled manner by using a dimer of dimethyl‐substituted glycoluril and a dimer of unsubstituted glycoluril. Coordination assemblies have been investigated by reactions between alkaline earth cations and o ‐TMeQ[6] in the presence of [CdCl 4 ] 2– , a structure inducer, in HCl aqueous solution. X‐ray diffraction analysis revealed that o ‐TMeQ[6] coordinates with Ca 2+ or Sr 2+ and forms centrosymmetric tetranuclear assemblies in the presence of [CdCl 4 ] 2– . [CdCl 4 ] 2– typically produces the “honeycomb effect” by forming honeycomb‐like frameworks, which assist metal ions in coordinating to o ‐TMeQ[6]. The driving forces of this effect are the “outer‐surface interactions” of cucurbit[ n ]urils.