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

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].