Phase equilibria in the fluorosilicic acid-o-phenylenediamine-water system at 25°C:: The crystal structure of o-phenylenediammonium hexafluorosilicate

The interactions in the H2SiF6-o-phenylenediamine-H2O (FSA-PDA-H2O) system at 25 degrees C is studied using the isothermal solubility method. The solid phases existing in the system are o-PDA (0-23.70 wt % H2SiF6) and hexafluorosilicate formulated as (o-PDAH(2))SiF6 (23.70-44.60 wt % H2SiF6). The structure for the latter is solved in single-crystal X-ray diffraction experiments. In the ionic structure of the complex, o-PDA cations and Si anions are linked through H-bonds NH center dot center dot center dot F(N center dot center dot center dot F2.865(2)-2.967(2) angstrom) into a two-dimensional net. The Si-F bond lengths are 1.6709(12)-1.6958(12) angstrom.