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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.

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(a) The mol­ecular units in the structure of ZnCl2·4.5H2O and (b) formation of a second coordination shell. Displacement ellipsoids are drawn at the 50% probability level. Dashed lines indicate hydrogen bonds.
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fig4: (a) The mol­ecular units in the structure of ZnCl2·4.5H2O and (b) formation of a second coordination shell. Displacement ellipsoids are drawn at the 50% probability level. Dashed lines indicate hydrogen bonds.

Mentions: Within the crystal structure of the 2.5-hydrate, there are two crystallographic different Zn2+ cations, as shown in Fig. 1 ▶. The Zn1 cation is octa­hedrally coordinated by five water mol­ecules and one chloride anion. The Zn2 cation is coordinated by four chloride anions, one shared with the Zn1 cation, leading to the formation of isolated [Zn2Cl4(H2O)5] units. Since the bond lengths of the bridging Cl atom of the tetra­hedron are shorter than to that of the octa­hedron, the latter becomes more distorted. The crystal structure of zinc chloride trihydrate consists of three crystallographically different Zn2+ cations (Fig. 2 ▶a). Two (Zn2 and Zn3) are located about an inversion centre and are coordinated octa­hedrally by six water mol­ecules, forming [Zn(H2O)6]2+ cations. The third one (Zn1) is tetra­hedrally coordinated by chlorine anions, [ZnCl4]2−. The polyhedra are not connected by sharing a single atom like in the 2.5-hydrate, but they are linked by hydrogen bonds (Fig. 2 ▶b). The octa­hedra and tetra­hedra are arranged in a CsCl-like arrangement with eight tetra­hedra located around one octa­hedron (Fig. 3 ▶a). As shown in Fig. 4 ▶a, in the asymmetric unit of ZnCl2·4.5H2O, two different Zn2+ cations are present. The Zn1 cation is coordinated octa­hedrally by six water mol­ecules and the Zn2 cation tetra­hedrally by four chloride anions. The three remaining water mol­ecules are hydrogen-bonded to a [Zn1(H2O]2+ octa­hedron (Fig. 4 ▶b).


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)

(a) The mol­ecular units in the structure of ZnCl2·4.5H2O and (b) formation of a second coordination shell. Displacement ellipsoids are drawn at the 50% probability level. Dashed lines indicate hydrogen bonds.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig4: (a) The mol­ecular units in the structure of ZnCl2·4.5H2O and (b) formation of a second coordination shell. Displacement ellipsoids are drawn at the 50% probability level. Dashed lines indicate hydrogen bonds.
Mentions: Within the crystal structure of the 2.5-hydrate, there are two crystallographic different Zn2+ cations, as shown in Fig. 1 ▶. The Zn1 cation is octa­hedrally coordinated by five water mol­ecules and one chloride anion. The Zn2 cation is coordinated by four chloride anions, one shared with the Zn1 cation, leading to the formation of isolated [Zn2Cl4(H2O)5] units. Since the bond lengths of the bridging Cl atom of the tetra­hedron are shorter than to that of the octa­hedron, the latter becomes more distorted. The crystal structure of zinc chloride trihydrate consists of three crystallographically different Zn2+ cations (Fig. 2 ▶a). Two (Zn2 and Zn3) are located about an inversion centre and are coordinated octa­hedrally by six water mol­ecules, forming [Zn(H2O)6]2+ cations. The third one (Zn1) is tetra­hedrally coordinated by chlorine anions, [ZnCl4]2−. The polyhedra are not connected by sharing a single atom like in the 2.5-hydrate, but they are linked by hydrogen bonds (Fig. 2 ▶b). The octa­hedra and tetra­hedra are arranged in a CsCl-like arrangement with eight tetra­hedra located around one octa­hedron (Fig. 3 ▶a). As shown in Fig. 4 ▶a, in the asymmetric unit of ZnCl2·4.5H2O, two different Zn2+ cations are present. The Zn1 cation is coordinated octa­hedrally by six water mol­ecules and the Zn2 cation tetra­hedrally by four chloride anions. The three remaining water mol­ecules are hydrogen-bonded to a [Zn1(H2O]2+ octa­hedron (Fig. 4 ▶b).

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