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

The recognition and separation of anions attracts attention from chemists, materials scientists, and engineers. Employing exo‐binding of artificial macrocycles to selectively recognize anions remains a challenge in supramolecular chemistry. We report the instantaneous co‐crystallization and concomitant co‐precipitation between [PtCl6]2− 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 [PtCl6]2− dianion recognition is driven by weak [Pt−Cl⋅⋅⋅H−C] hydrogen bonding and [Pt−Cl⋅⋅⋅C=O] ion–dipole interactions. The synthetic protocol is highly selective. Recognition is not observed in combinations between cucurbit[6]uril and six other Pt‐ and Pd‐ or Rh‐based chloride anions. We also demonstrated that cucurbit[6]uril is able to separate selectively [PtCl6]2− dianions from a mixture of [PtCl6]2−, [PdCl4]2−, and [RhCl6]3− anions. This protocol could be exploited to recover platinum from spent vehicular three‐way catalytic converters and other platinum‐bearing metal waste. [ABSTRACT FROM AUTHOR]