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Crystal structures of ZnCl2·2.5H2O, ZnCl2·3H2O and ZnCl2·4.5H2O.

Hennings E, Schmidt H, Voigt W - Acta Crystallogr Sect E Struct Rep Online (2014)

Bottom Line: The [ZnCl4] tetra-hedra and [Zn(H2O)6] octa-hedra are arranged in alternating rows parallel to [001].The structure of the 4.5-hydrate {hexa-aqua-zinc tetra-chlorido-zinc trihydrate, [Zn(H2O)6][ZnCl4]·3H2O}, consists of isolated octa-hedral [Zn(H2O)6] and tetra-hedral [ZnCl4] units, as well as additional lattice water mol-ecules.O-H⋯O hydrogen bonds between the water mol-ecules as donor and ZnCl4 tetra-hedra and water mol-ecules as acceptor groups leads to the formation of a three-dimensional network in each of the three structures.

View Article: PubMed Central - HTML - PubMed

Affiliation: TU Bergakademie Freiberg, Institute of Inorganic Chemistry, Leipziger Strasse 29, D-09596 Freiberg, Germany.

ABSTRACT
The formation of different complexes in aqueous solutions is an important step in understanding the behavior of zinc chloride in water. The structure of concentrated ZnCl2 solutions is governed by coordination competition of Cl(-) and H2O around Zn(2+). According to the solid-liquid phase diagram, the title compounds were crystallized below room temperature. The structure of ZnCl2·2.5H2O contains Zn(2+) both in a tetra-hedral coordination with Cl(-) and in an octa-hedral environment defined by five water mol-ecules and one Cl(-) shared with the [ZnCl4](2-) unit. Thus, these two different types of Zn(2+) cations form isolated units with composition [Zn2Cl4(H2O)5] (penta-aqua-μ-chlorido-tri-chlorido-di-zinc). The trihydrate {hexa-aqua-zinc tetra-chlorido-zinc, [Zn(H2O)6][ZnCl4]}, consists of three different Zn(2+) cations, one of which is tetra-hedrally coordinated by four Cl(-) anions. The two other Zn(2+) cations are each located on an inversion centre and are octa-hedrally surrounded by water mol-ecules. The [ZnCl4] tetra-hedra and [Zn(H2O)6] octa-hedra are arranged in alternating rows parallel to [001]. The structure of the 4.5-hydrate {hexa-aqua-zinc tetra-chlorido-zinc trihydrate, [Zn(H2O)6][ZnCl4]·3H2O}, consists of isolated octa-hedral [Zn(H2O)6] and tetra-hedral [ZnCl4] units, as well as additional lattice water mol-ecules. O-H⋯O hydrogen bonds between the water mol-ecules as donor and ZnCl4 tetra-hedra and water mol-ecules as acceptor groups leads to the formation of a three-dimensional network in each of the three structures.

No MeSH data available.


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The connection of individual [Zn2Cl4(H2O)5] units through hydrogen bonds (dashed lines) in the structure of ZnCl2·2.5H2O.
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fig5: The connection of individual [Zn2Cl4(H2O)5] units through hydrogen bonds (dashed lines) in the structure of ZnCl2·2.5H2O.

Mentions: In the structure of ZnCl2·2.5H2O, all terminal Cl− anions are connected to the octa­hedral parts of neighbouring [Zn2Cl4(H2O)5] units by three O—H⋯Cl hydrogen bonds per anion (Table 1 ▶, Fig. 5 ▶). The coordination polyhedra in the trihydrate are arranged in zigzag chains parallel to [001] in the crystal structure. The chains are highlighted in different shades of colors in Fig. 3 ▶b. Hydrogen bonds (Table 2 ▶) are established within one chain and between neighbouring chains (not shown in the Figure). As can be seen from Fig. 4 ▶b, five water mol­ecules in the crystal structure of ZnCl2·4.5H2O are connected via hydrogen bonds to the [Zn1(H2O]2+ octa­hedron, three of them at the axial coordination sites and two of them at the equatorial coordination sites. Seven chloride anions from [Zn2Cl4]2− tetra­hedra contribute to the second coordination sphere of Zn1. Thus, every coordinating water mol­ecule forms two hydrogen bonds. The structural situation in this salt can be compared with the second coordination shells around magnesium in magnesium halide nonahydrates like MgBr2·9H2O or MgI2·9H2O (Hennings et al., 2013 ▶). Each water mol­ecule of the [Mg(H2O)6]2+ octa­hedra forms two hydrogen bonds, thus six water mol­ecules and six halide atoms are involved in the second shell. However, in case of the magnesium halides each water mol­ecule donates a hydrogen bond towards a halide anion and towards another water mol­ecule. The hydrogen-bond geometry in ZnCl2·4.5H2O is given inTable 3 ▶.


Crystal structures of ZnCl2·2.5H2O, ZnCl2·3H2O and ZnCl2·4.5H2O.

Hennings E, Schmidt H, Voigt W - Acta Crystallogr Sect E Struct Rep Online (2014)

The connection of individual [Zn2Cl4(H2O)5] units through hydrogen bonds (dashed lines) in the structure of ZnCl2·2.5H2O.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4257420&req=5

fig5: The connection of individual [Zn2Cl4(H2O)5] units through hydrogen bonds (dashed lines) in the structure of ZnCl2·2.5H2O.
Mentions: In the structure of ZnCl2·2.5H2O, all terminal Cl− anions are connected to the octa­hedral parts of neighbouring [Zn2Cl4(H2O)5] units by three O—H⋯Cl hydrogen bonds per anion (Table 1 ▶, Fig. 5 ▶). The coordination polyhedra in the trihydrate are arranged in zigzag chains parallel to [001] in the crystal structure. The chains are highlighted in different shades of colors in Fig. 3 ▶b. Hydrogen bonds (Table 2 ▶) are established within one chain and between neighbouring chains (not shown in the Figure). As can be seen from Fig. 4 ▶b, five water mol­ecules in the crystal structure of ZnCl2·4.5H2O are connected via hydrogen bonds to the [Zn1(H2O]2+ octa­hedron, three of them at the axial coordination sites and two of them at the equatorial coordination sites. Seven chloride anions from [Zn2Cl4]2− tetra­hedra contribute to the second coordination sphere of Zn1. Thus, every coordinating water mol­ecule forms two hydrogen bonds. The structural situation in this salt can be compared with the second coordination shells around magnesium in magnesium halide nonahydrates like MgBr2·9H2O or MgI2·9H2O (Hennings et al., 2013 ▶). Each water mol­ecule of the [Mg(H2O)6]2+ octa­hedra forms two hydrogen bonds, thus six water mol­ecules and six halide atoms are involved in the second shell. However, in case of the magnesium halides each water mol­ecule donates a hydrogen bond towards a halide anion and towards another water mol­ecule. The hydrogen-bond geometry in ZnCl2·4.5H2O is given inTable 3 ▶.

Bottom Line: The [ZnCl4] tetra-hedra and [Zn(H2O)6] octa-hedra are arranged in alternating rows parallel to [001].The structure of the 4.5-hydrate {hexa-aqua-zinc tetra-chlorido-zinc trihydrate, [Zn(H2O)6][ZnCl4]·3H2O}, consists of isolated octa-hedral [Zn(H2O)6] and tetra-hedral [ZnCl4] units, as well as additional lattice water mol-ecules.O-H⋯O hydrogen bonds between the water mol-ecules as donor and ZnCl4 tetra-hedra and water mol-ecules as acceptor groups leads to the formation of a three-dimensional network in each of the three structures.

View Article: PubMed Central - HTML - PubMed

Affiliation: TU Bergakademie Freiberg, Institute of Inorganic Chemistry, Leipziger Strasse 29, D-09596 Freiberg, Germany.

ABSTRACT
The formation of different complexes in aqueous solutions is an important step in understanding the behavior of zinc chloride in water. The structure of concentrated ZnCl2 solutions is governed by coordination competition of Cl(-) and H2O around Zn(2+). According to the solid-liquid phase diagram, the title compounds were crystallized below room temperature. The structure of ZnCl2·2.5H2O contains Zn(2+) both in a tetra-hedral coordination with Cl(-) and in an octa-hedral environment defined by five water mol-ecules and one Cl(-) shared with the [ZnCl4](2-) unit. Thus, these two different types of Zn(2+) cations form isolated units with composition [Zn2Cl4(H2O)5] (penta-aqua-μ-chlorido-tri-chlorido-di-zinc). The trihydrate {hexa-aqua-zinc tetra-chlorido-zinc, [Zn(H2O)6][ZnCl4]}, consists of three different Zn(2+) cations, one of which is tetra-hedrally coordinated by four Cl(-) anions. The two other Zn(2+) cations are each located on an inversion centre and are octa-hedrally surrounded by water mol-ecules. The [ZnCl4] tetra-hedra and [Zn(H2O)6] octa-hedra are arranged in alternating rows parallel to [001]. The structure of the 4.5-hydrate {hexa-aqua-zinc tetra-chlorido-zinc trihydrate, [Zn(H2O)6][ZnCl4]·3H2O}, consists of isolated octa-hedral [Zn(H2O)6] and tetra-hedral [ZnCl4] units, as well as additional lattice water mol-ecules. O-H⋯O hydrogen bonds between the water mol-ecules as donor and ZnCl4 tetra-hedra and water mol-ecules as acceptor groups leads to the formation of a three-dimensional network in each of the three structures.

No MeSH data available.


Related in: MedlinePlus