Metallo-Cryptophanes Decorated with Bis-N-Heterocyclic Carbene Ligands: Self-Assembly and Guest Uptake into a Nonporous Crystalline Lattice

Pd₃L₂ metallo-cryptophane cages with cyclotriveratrylene-type L ligands can be stabilized by use of a bis-N-heterocyclic carbene as an auxiliary cis-protecting ligand, while use of more common protecting chelating ligands such as ethylenediamine saw a Pd₃L₂ to Pd₆L₈ rearrangement occur in solution. The crystalline Pd₃L₂ complexes act as sponges, taking up 1,2-dichorobenzene or iodine in a single-crystal-to-single-crystal fashion despite not exhibiting conventional porosity.