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Tetra-ammine-(carbonato-κ(2) O,O')cobalt(III) nitrate: a powder X-ray diffraction study.
1Université du Maine, Institut des Molécules et des Matériaux du Mans, CNRS UMR 6283, 72085 Le Mans, France.
Acta Crystallographica. Section E, Structure Reports Online
|September 19, 2013
Summary
Researchers characterized the anhydrous form of a cobalt complex, [Co(CO3)(NH3)4]NO3, revealing its structure and hydrogen bonding. Dehydration of the hemihydrate form results in a surprising volume increase.
Area of Science:
- Inorganic Chemistry
- Crystallography
- Materials Science
Background:
- University practical chemistry courses often aim to synthesize [Co(CO3)(NH3)4]NO3 but typically yield only the hemihydrated form.
- The structure and properties of the anhydrous form of this cobalt complex have not been fully elucidated.
Purpose of the Study:
- To prepare and characterize the anhydrous form of [Co(CO3)(NH3)4]NO3.
- To elucidate the crystal structure of the anhydrous phase and compare it with the hemihydrate form.
- To investigate the dehydration process and its effect on the material's volume.
Main Methods:
- Single-crystal X-ray diffraction was used to determine the crystal structure of the anhydrous [Co(CO3)(NH3)4]NO3.
- Structural comparison between the anhydrous and hemihydrate forms was performed.
- Analysis of hydrogen bonding networks was conducted.
Main Results:
- The anhydrous [Co(CO3)(NH3)4]NO3 was successfully prepared and its crystal structure determined.
- The Co(III) ion exhibits octahedral O2N4 coordination with a chelating carbonate group and four ammine ligands.
- An intricate network of N-H⋯O hydrogen bonds was observed, involving both carbonate and nitrate groups.
- The anhydrous structure is similar to the hemihydrate phase, suggesting a topotactic dehydration reaction.
- The dehydration process results in an unusual 4.3% volume increase.
Conclusions:
- The anhydrous form of [Co(CO3)(NH3)4]NO3 possesses a distinct crystal structure characterized by extensive hydrogen bonding.
- The dehydration of the hemihydrate to the anhydrous form proceeds via a topotactic mechanism with a significant volume expansion.
- This study provides a detailed structural understanding of the anhydrous cobalt complex and its dehydration behavior.
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