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

Formation of the unexpected hexafluorosilicate (SiF 6 2- ) anion during crystallization via self-assembly in glassware is scrutinized. Self-assembly of M(BF 4 ) 2 (M 2+ = Cu 2+ and Zn 2+ ) with tridentate N-donors (L) in a mixture solvent including methanol in a glass vessel gives rise to an SiF 6 2- -encapsulated Cu 3 L 4 double-decker cage and a Zn 2 L 4 cage, respectively. Induced reaction of CuX 2 (X - = PF 6 - and SbF 6 - ) instead of Cu(BF 4 ) 2 , with the tridentate ligands, produces the same species. The formation time of SiF 6 2- is in the order of anions BF 4 - < PF 6 - < SbF 6 - under the given reaction conditions. The SiF 6 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 SiO 2 of the surface of the glass vessel.