Synthesis, Crystal Structures, and Thermal Properties of Protic Metal-Containing Ionic Liquids, Diethanolammonium Halometallates: (HOCH₂CH₂)₂NH₂FeCl₄ and ((HOCH₂CH₂)₂NH₂)₂CoCl₄

Abstract

Protic metal-containing ionic liquids with the diethanolammonium cation (HO–CH₂–CH₂)₂${\text{NH}}_{{\text{2}}}^{ + }$ (DEAH⁺) and anions ${\text{FeCl}}_{{\text{4}}}^{-}$ and ${\text{CoCl}}_{{\text{4}}}^{{{\text{2}}-}}$ (DEAHFeCl₄ (I), (DEAH)₂CoCl₄ (II)) are synthesized. The crystal structures of compounds I and II are determined by X-ray structure analysis (CIF files CCDC nos. 1957208 (I) and 1957189 (II)). Compound I has a layered structure. The layer consists of the DEAH⁺ cations with the disordered system of hydrogen bonds and attached ${\text{FeCl}}_{{\text{4}}}^{-}$ anions. The structure of compound II represents a three-dimensional framework consisting of the DEAH⁺ cations and ${\text{CoCl}}_{{\text{4}}}^{{{\text{2}}-}}$ anions linked by hydrogen bonds. The thermal analysis shows that the melting points of compounds I (45°С) and II (55°С) are lower than 100°С, the enthalpy of melting of compound I is higher than that of compound II, and the decomposition temperature of compound II (210°С) is higher than that of compound I (128°C).