The products of reaction of fluorosilicic acid (FSA) with organic bases, the fluorosilicates of the relevant "onium" cations, find an application as anti-caries agents, ionic liquids, reagents for modified zeolite catalytic agents, in the synthesis of the complexes of silicon tetrafluoride, fungicides, or in preparation of herbicide-containing mixtures [1]. On the other hand these compounds are of interest for stabilization of various fluorido complexes of silicon, the products of the hydrolytic transformations of FSA [2]. In the process of study of FSA interaction with bidentate ligands L = 2,2′-bipyridine (2,2′-Bipy) and 1,10-phenanthroline it was found that the products of reactions are mixtures of the corresponding hexafluorosilicates and molecular cis-chelate silicon tetrafluoride complexes: H2SiF6 (aq) + L (MeOH) → (LH2)SiF6 + cis-[SiF4(L)] In the case of reaction system H2SiF6 – 2,2′-Bipy – H2O – MeOH both products of interaction – salt (2,2′-BipyH2)SiF6 (I) as a dominant form and complex cis-[SiF4(2,2′-Bipy)] (II) as a by-product were identified by X-ray crystallography: I II It is known that the silicon tetrafluoride complexes with N-donor ligands reveal extremely low hydrolytic stability, therefore their synthesis by interaction of SiF4 with ligands is carried out in anhydrous solvents or in gas phase [3]. Even in the humid air complexes tend to be converted into the corresponding hexafluorosilicates. Evidently, the detection of complex II as a by-product of I crystallized from organic-aqueous solution, is provided by the chelating ligand effect. Compound II represents the first structurally confirmed example of molecular complex formed by SiF4 with Ndonor ligand separated from the mixed aqueous-organic medium, which retains its structure after recrystallization from aqueous solution.