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New refinement of the crystal structure of Zn(NH3)2Cl2 at 100?K.

ABSTRACT: The crystal structure of [ZnCl2(NH3)2], diamminedi-chlorido-zinc, was re-investigated at low temperature, revealing the positions of the hydrogen atoms and thus a deeper insight into the hydrogen-bonding scheme in the crystal packing. In comparison with previous crystal structure determinations [MacGillavry & Bijvoet (1936 ?). Z. Kristallogr. 94, 249-255; Yamaguchi & Lindqvist (1981 ?). Acta Chem. Scand. 35, 727-728], an improved precision of the structural parameters was achieved. In the crystal, tetra-hedral [Zn(NH3)2Cl2] units (point-group symmetry mm2) are linked through N-H?Cl hydrogen bonds into a three-dimensional network.

SUBMITTER: Ivsic T

PROVIDER: S-EPMC6727043 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature

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New refinement of the crystal structure of Zn(NH3)2Cl2 at 100 K.

Ivšić Trpimir T Bi David Wenhua DW Magrez Arnaud A

Acta crystallographica. Section E, Crystallographic communications 20190830 Pt 9

The crystal structure of [ZnCl2(NH3)2], diamminedi-chlorido-zinc, was re-investigated at low temperature, revealing the positions of the hydrogen atoms and thus a deeper insight into the hydrogen-bonding scheme in the crystal packing. In comparison with previous crystal structure determinations [MacGillavry & Bijvoet (1936 ▸). Z. Kristallogr. 94, 249-255; Yamaguchi & Lindqvist (1981 ▸). Acta Chem. Scand. 35, 727-728], an improved preci ...[more]

PMID: 31523472

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Project description:This study aims to solve the site-occupancy issues of any crystalline substance, showing that the structure refinement results should not be limited to a simple description of the crystal geometry but should go beyond that, providing refined site-scattering values consistent with the chemical data. A detailed description of the structure of the amphibole-supergroup minerals is very challenging owing to their complex chemical composition that renders the process of cation partition extremely difficult, particularly because of the occurrence of multivalent elements. Since amphiboles naturally occur under a fibrous morphology and have largely been used to produce asbestos, there is a growing demand for detailed and accurate structural data in order to study the relationships between structure, composition and toxicity. The present study proposes a recommended refinement procedure for both X-ray single-crystal structure refinement (SREF) and Rietveld analysis for tremolite, selected as a test case. The corresponding structural results are compared to estimate the ‘degree of confidence’ of the Rietveld refinement with regard to SREF. In particular, it is shown that the interpretation of the electron density of the tremolite structure by SREF is model dependent. By assuming that the site-scattering values from SREF should be as close as possible to those from electron microprobe analysis, as a crucial constraint for the correct description of the final crystal-chemical model, it is found that it is best satisfied by using partially ionized scattering curves (SCs) for O and Si, and neutral SCs (neutral oxygen curves or NOCs) for other atoms. This combination leads to the best fit to the diffraction data. Moreover, it is found that Rietveld refinement using NOCs produces the best structural results, in excellent agreement with SREF. It is worth noting that, due to the complexity of the diffraction pattern and the fairly large number of freely refinable parameters, refinements with different combinations of SCs produce results almost indistinguishable from a statistical point of view, albeit showing significant differences from a structural point of view.

Dataset Information

New refinement of the crystal structure of Zn(NH3)2Cl2 at 100?K.

Publications

New refinement of the crystal structure of Zn(NH<sub>3</sub>)<sub>2</sub>Cl<sub>2</sub> at 100 K.

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