Trimetallic coordination cage formation for nitrate encapsulation: transformation of kinetic products into thermodynamic products

Abstract

A procedure for the formation of a nitrate-encapsulating tripalladium(II) cage via self-assembly of Pd(NO₃)₂ with 1,3-bis(dimethyl(pyridin-4-yl)silyl)propane (L) was developed. The self-assembly reaction initially produces spiro-type macrocycles, PdL₂, and finally results in transformation into a nitrate-encapsulated cage, [(NO₃)@Pd₃L₆], in the mother liquor. The reaction of PdX₂ (X⁻ = BF₄⁻, ClO₄⁻, PF₆⁻, and CF₃SO₃⁻ instead of NO₃⁻) with L gives rise to a spiro species, PdL₂, as the final product, and anion exchange of the spiro products, [PdL₂](X)₂, with NO₃⁻ produces the tripalladium cage [(NO₃)@Pd₃L₆].