Selective Separation of Hexachloroplatinate(IV) Dianions Based on Exo‐Binding with Cucurbit[6]uril

Abstract

The recognition and separation of anions attracts attention from chemists,m aterials scientists,a nd engineers. Employing exo-binding of artificial macrocycles to selectively recognizea nions remains ac hallenge in supramolecular chemistry.W er eport the instantaneous co-crystallization and concomitant co-precipitation between [PtCl 6 ] 2À dianions and cucurbit[6]uril, which relies on the selective recognition of these dianions through noncovalent bonding interactions on the outer surface of cucurbit[6]uril. The selective [PtCl 6 ] 2À dianion recognition is driven by weak [PtÀCl•••HÀC] hydrogen bonding and [Pt À Cl•••C = O] ion-dipole interactions.T he synthetic protocol is highly selective.R ecognition is not observed in combinations between cucurbit[6]uril and six other Pt-and Pd-or Rh-based chloride anions.W ea lso demonstrated that cucurbit[6]uril is able to separate selectively [PtCl 6 ] 2À dianions from amixture of [PtCl 6 ] 2À ,[PdCl 4 ] 2À ,and [RhCl 6 ] 3À anions.T his protocol could be exploited to recover platinum from spent vehicular three-wayc atalytic converters and other platinum-bearing metal waste.