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  Home > JCE Print > Journal of Chemical Education > Issues > 1997  > April  >
In the Laboratory
Chromium (III) Acetate, Chromium (III) Acetate Hydroxide, or µ3-Oxo-esakis-(µ2-acetato-O,O') - triaqua-trichromium (III) Acetate? Determining the Structure of a Complex Compound by Analytical and Spectroscopic Methods
Liliana Strinna Erre, Giovanni Micera, Tadeusz Glowiak, and Henry Kozlowski
Department of Chemistry, University of Sassari, Via Vienna 2, 07100 Sassari, Italy

Cover
April 1997
Vol. 74 No. 4
p. 432

Abstract
An experiment illustrating the use of infrared spectroscopy and model compounds to elucidate the structure of chromium (III) acetate is reported. Two commercial samples with the following conventional formulations Cr3(CH3CO2)7(OH)2 and Cr(CH3CO2)3 were examined and compared to the model compound [Cr32-CH3COO)63-O)(H2O)3]DHB·2H2O, DHB = 2,6-dihydroxybenzoate(1-). The experiment may serve to illustrate the advantage of the joint application of analytical and spectroscopic data, in particular the use of symmetry concepts and IR-Raman selection rules, in the assignment of inorganic structures.

All the samples exhibit the distinctive vibrational features predicted for a trimetallic carboxylate complex with the µ3-O-Cr3 cage. Therefore, it may be concluded that chromium (III) acetates are endowed with a trimetallic arrangement where six acetates bridge three metal ions connected by a triply-bridging oxygen so that a total of four carboxylate oxygens surround each chromium ion. Water molecules act as the terminal ligands and complete an almost regular octahedral coordination polyhedron at each metal center. Analytical data are in good agreement with the [Cr32-CH3COO)6(m3-O)(CH3COO) composition.

More Information
*  Citation
Erri, Liliana Strinna; Micera, Giovanni; Glowiak, Tadeusz; Kozlowski, Henry. J. Chem. Educ. 1997 74 432.
*  Keywords
*  History
Created:
Last Updated:
July 28, 1999
June 23, 2005
  Home > JCE Print > Journal of Chemical Education > Issues > 1997 > April > Page 432


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