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(NO 3 ) 2 with 1,3-bis(dimethyl(pyridin-4-yl)silyl)propane (L) was developed. The self-assembly reaction initially produces spiro-type macrocycles, PdL 2 , and finally results in transformation into a nitrate-encapsulated cage, [(NO 3 )@Pd 3 L 6 ], in the mother liquor. The reaction of PdX 2 (X − = BF 4 − , ClO 4 − , PF 6 − , and CF 3 SO 3 − instead of NO 3 − ) with L gives rise to a spiro species, PdL 2 , as the final product, and anion exchange of the spiro products, [PdL 2 ](X) 2 , with NO 3 − produces the tripalladium cage [(NO 3 )@Pd 3 L 6 ]. The self-assembly of Pd(NO 3 ) 2 with 1,3-bis(dimethyl(pyridin-4-yl)silyl)propane (L) initially produces the nitrate-encapsulated cage [(NO 3 )@Pd 3 L 6 ] via the spiro-type macrocyclic kinetic product.