Аннотация:The extraction of tetrafl uoroboric acid from aqueous solutions to a solution of benzo-15crown-5 (B15С5, 1 mol L–1) in chloroform is shown to occur due to complexation with the ratio of components HBF4 : B15С5 = 1 : 1.5. It was revealed by IR spectroscopy that the whole crown ether in the extract is coordinated. The 1 : 1 HBF4•В15С5 complex was isolated and characterized using IR spectroscopy and Х-ray diff raction analysis. The O(2) and O(4) atoms of the crown ether ring participate in the coordination.