Amino acid hexafluorosilicates – an overview

Abstract

Abstract Single crystal data on eight new hexafluorosilicate salts of amino acids are presented in this work. This includes crystal and molecular structures of the following salts: 2 β-Ala · H2SiF6 (I), 2 Bet · H2SiF6 (II), 2L-Orn · H2SiF6 (III), 2L-Ser · H2SiF6 (IV), 2L-Leu · H2SiF6 · 2 H2O (V), 2L-Ile · H2SiF6 · 2 H2O (VI), 2L-Met · H2SiF6 · H2O (VII), and 2L-Asp · H2SiF6 · 2 H2O (VIII). In all these crystals, the SiF6-anion is ordered, except for (III), where disorder of the fluorine atoms occurs. An analysis of previously published data on amino acid hexafluorosilicates showed that the amount of hydrogen bonding towards the SiF6-anion is an indication of disorder – we found that all structures with 0.6 or less hydrogen bonds per fluorine atom have disorder.