Crystal structures of hydrates of simple inorganic salts. I. Water-rich magnesium halide hydrates MgCl₂·8H₂O, MgCl₂·12H₂O, MgBr₂·6H₂O, MgBr₂·9H₂O, MgI₂·8H₂O and MgI₂·9H₂O

Abstract

The previously reported structures of the hydrates of simple inorganic salts that crystallize at room temperature are generally well determined. This is not true for water-rich hydrates, which crystallize at temperatures below 273 K. In this series, investigations of the crystal structures of water-rich hydrates crystallized from aqueous solutions at low temperatures are presented. Reported herein are the structures of a set of magnesium salts. Crystals of MgCl2·8H2O (magnesium dichloride octahydrate), MgCl2·12H2O (magnesium dichloride dodecahydrate), MgBr2·6H2O (magnesium dibromide hexahydrate), MgBr2·9H2O (magnesium dibromide nonahydrate), MgI2·8H2O (magnesium diiodide octahydrate) and MgI2·9H2O (magnesium diiodide nonahydrate) were grown from their aqueous solutions at temperatures below 298 K according to the solid-liquid phase diagrams. All structures are built up from Mg(H2O)6 octahedra. Dimensions and angles in the hexaaqua cation complexes are very similar and variation is not systematic. The anions are incorporated into a specific network of O-H...X hydrogen bonds.

Structure, thermal expansion and incompressibility of MgSO4·9H2O, its relationship to meridianiite (MgSO4·11H2O) and possible natural occurrences

“…However, it appears that these are substantially less common than finite branched and unbranched chains. Branched or decorated (H 2 O) 9 chains occur in both trivalent and divalent metal bromide and iodide enneahydrates (Hennings et al, 2013;Schmidt et al, 2014), whereas branched (H 2 O) 8 chains appear in CaBr 2 .9H 2 O (Hennings et al, 2014b). Of course, the principal difference with our title compound is the 1:2 or 1:3 cation-to-anion ratio in these other materials.…”

Nucleobase carbonyl groups are poor Mg2+inner-sphere binders but excellent monovalent ion binders—a critical PDB survey

“…The water exclusion zones and the second coordination shells are marked by gray and blue rectangles, respectively. (B) Ultra-high-accuracy X-ray structures of Mg(H 2 O) 6 2+ (top) and Na(H 2 O) 6 + (bottom) illustrating similarities between Mg 2+ and Na + octahedral first hydration shells (Gerasimchuk and Dalley 2004;Hennings et al 2013). (C ) In scale schematic representation of the radius of the Mg(H 2 O) 6 2+ (green) and Na(H 2 O) 6 + (magenta) first cordination shells.…”

MIR, VNIR, NIR, and Raman spectra of magnesium chlorides with six hydration degrees: Implication for Mars and Europa

“…The Cl atoms act as bridging ligands, occupying the four equatorial and one of the axial positions (Mg─Cl bond length We draw the structure of (MgCl 2 •nH 2 O, n = 6, 8, 12) based on the structural refinement data of MgCl 2 •nH 2 O (n = 6, 8, 12). [28,29] In the structure of MgCl Tables 1 and 2) consist the peaks from the fundamental vibrational modes of structural H 2 O and the lattice vibrational modes of these crystals. These spectra can be divided into three sections and discussed separately, focusing on the H 2 O stretching (3,800-2,900 cm −1 ; Figure 4a), H 2 O bending (2,500-1,400 cm −1 ; Figure 4b), and H 2 O libration and lattice vibrations (1,300-100 cm −1 ; Figure 4c).…”