Reversible formation and cleavage of Pt→Ag dative bonds in a pre-organized cavity of a luminescent heteropolynuclear platinum(ii) complex

Abstract

A U-shaped Pt₂Ag₂ complex [Pt₂Ag₂(ppy)₂(Ph₂pz)₄] with a pre-organized cavity (ppy = 2-phenylpridinate and Ph₂pz = 3,5-diphenylpyrazolate) and related complexes have been prepared. The Pt₂Ag₂ complexes react with Ag(I) ions to give the corresponding Pt₂Ag₃ complexes containing Pt→Ag dative bonds. It became obvious that the existence of the C(ipso) atom in the chelate ligand is important as the driving force for forming Pt→Ag dative bonds. However, once the Pt₂Ag₃ complex is formed, the trapped Ag(I) ion is mainly stabilized by the Pt→Ag dative bonds, which are stronger than the Ag–C(ipso) bond. The trapped Ag(I) ion can be abstracted from the cavity selectively by adding an equivalent amount of chloride ion into the solution of Pt₂Ag₃ complexes to reproduce the original Pt₂Ag₂ complexes.