Coordination of silicon tetrafluoride with pyridine and other nitrogen electron-pair donor molecules

Abstract

Silicon tetrafluoride reacts with pyridine, pyrrolidine, and piperidine forming solid 1:2 complexes. With ethylenediamine, the stable 1:1 complex results. These compounds are easily hydrolyzed and sublimed and have no measurable vapor pressure at 25°. Hydrolysis of SiF₄•2C₅H₅N with aqueous HF produces pyridinium hexafluorosilicate (4), (C₅H₅NH⁺)₂SiF₆²⁻. Ethylenediamine readily displaces pyridine from SiF₄•2C₅H₅N, forming SiF₄•NH₂(CH₂)₂NH₂. Infrared spectra of the complexes are compared in the 900–280 cm⁻¹ region, but it was not possible to decide whether the pyrrolidine and piperidine complexes are cis- or trans-octahedral.