Crystal structure and chemical oxidation of the palladium(II) cyclam complex within the cavity of cucurbit[8]uril

Inclusion compound of a macrocyclic cavitand cucurbit[8]uril (C48H48N32O16, CB[8]) with a square-planar palladium(II) complex of a polyamine ligand cyclam, {[Pd(cyclam)]@CB[8]}Cl2·16⅓H2O (1), was synthesized and characterized by X-ray crystallography, elemental analysis, IR, and electrospray ionization (ESI) mass spectrometry. The complex [Pd(cyclam)]2+ undergoes chemical oxidation within the CB[8] cavity leading to the formation of the palladium(IV) inclusion compound {trans-[Pd(cyclam)Cl2]@CB[8]}Cl2·14H2O (2). The Pd(II) and Pd(IV) complexes are completely encapsulated within the CB[8] cavity. The cyclam ring in 1 and 2 adopts the most stable configuration (trans-III (S,S,R,R)).