Insight into systematic formation of hexafluorosilicate during crystallization via self-assembly in a glass vessel.

Formation of the unexpected hexafluorosilicate (SiF6 2- ) anion during crystallization via self-assembly in glassware is scrutinized. Self-assembly of M(BF4 )2 (M2+ = Cu2+ and Zn2+ ) with tridentate N-donors (L) in a mixture solvent including methanol in a glass vessel gives rise to an SiF6 2- -encapsulated Cu3 L4 double-decker cage and a Zn2 L4 cage, respectively. Induced reaction of CuX2 (X- = PF6 - and SbF6 - ) instead of Cu(BF4 )2 , with the tridentate ligands, produces the same species. The formation time of SiF6 2- is in the order of anions BF4 - < PF6 - < SbF6 - under the given reaction conditions. The SiF6 2- anion, acting as a cage template or cage-to-cage bridge, seems to be formed from the reaction of polyatomic anions containing fluoride with the SiO2 of the surface of the glass vessel.