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Chemical accuracy and precision in Rietveld analysis: The crystal structure of cobalt(II) acetate tetrahydrate

Published online by Cambridge University Press:  10 January 2013

James A. Kaduk  and
Walt Partenheimer
James A. Kaduk
Affiliation:
Amoco Corporation, P.O. Box 3011, MC F-9, Naperville, Illinois 60566
Walt Partenheimer
Affiliation:
Amoco Corporation, P.O. Box 3011, MC F-9, Naperville, Illinois 60566
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Abstract

The crystal structure of cobalt(II) acetate tetrahydrate, Co(C2H3O2)·4H2O, has been refined using single-crystal, laboratory powder, and synchrotron powder diffraction data, both individually and in various combinations. The compound crystallizes in the monoclinic space group P21/c, with a=4.80688(3), b=11.92012(7), c=8.45992(5) Å, β=94.3416(4)° at 27 °C, and Z=2. The crystal structure consists of discrete centrosymmetric trans-Co(C2H3O2)(H2O)4 complexes, linked by a three-dimensional network of hydrogen bonds. Each complex participates in 14 hydrogen bonds, 12 intermolecular, and 2 intramolecular. Compared to the single-crystal refinement, refinement of laboratory powder data yielded an average difference in bond distances of 0.02 Å, in bond angles of 3°, and in root mean square atomic displacements of 0.07 Å. The standard uncertainties of the bond distances were 0.01 Å, compared to the 0.001–0.002 Å in the single-crystal refinement. Refinement of the synchrotron powder data yielded improved accuracy and precision. It proved impossible to locate or refine hydrogen positions using a single-powder dataset, but the hydrogens could be refined using rigid groups in a joint refinement of the two powder datasets. Even from powder refinements, it is possible to obtain suitable accuracy and precision to distinguish C–O and C=O bonds, and to examine details of chemical bonding.

Type
Research Article
Information
Powder Diffraction , Volume 12 , Issue 1 , March 1997 , pp. 27 - 39
Copyright
Copyright © Cambridge University Press 1997

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