Nitropentaamminecobalt(III) chloride

Nitropentaamminecobalt(III) chloride is an inorganic compound with the molecular formula [Co(NH3)5(NO2)]Cl2. It is an orange solid that is soluble in water. Although it has no applications, the compound has been of academic interest as a source of the coordination complex [Co(NH3)5(NO2)]2+.

Nitropentaamminecobalt(III) chloride
Identifiers
Properties
H15N6O2Cl2Co
Molar mass 261.00 g/mol
Density 1.83 g/mL[1]
Hazards
Xi
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Linkage isomers

The coordination complexes [Co(NH3)5(NO2)]2+ and [Co(NH3)5(ONO)]2+ provided an early example of linkage isomerism. This nitritopentaamminecobalt(III) isomer converts to the more stable nitro form at room temperature.[2] The two isomers can be distinguished by UV-Vis spectroscopy. Absorbance maxima for the nitro isomer occur at 457.5, 325, and 239 nm. The nitrito has maxima at 486, 330, and 220 nm.[3] Their IR spectra also differ. The nitrito isomer absorbs at 1460 and 1065 cm−1. The nitro isomer absorbs at 1430 and 825 cm−1.[4]

Preparation and reactions

Nitritopentaamminecobalt(III) chloride is prepared by treating chloropentamminecobalt chloride with sodium nitrite:

[Co(NH3)5Cl]2+ + NO2− → [Co(NH3)5(ONO)]2+ + Cl−

Heating a solution of the nitrito complex gives the nitro isomer.

Nitropentaamminecobalt(III) chloride has been studied for its ability to repress cell division.[5] This property has been tested to inhibit the growth of tumors and bacteria such as E. coli. However, it has been found that several other compounds are superior inhibitors.

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References
  1. Grenthe, I; Nordin, E. (1979). "Nitrito-Nitro Linkage Isomerization in the Solid State. 2. A Comparative Study of the Structures of Nitrito- and Nitropentaamminecobalt( 111) Dichloride". Inorganic Chemistry. 18 (7): 1869–74. doi:10.1021/ic50197a031.
  2. Hohman, W. H. (1974). "A Combined Infrared and Kinetic Study of Linkage Isomers. An Inorganic Experiment". Journal of Chemical Education. 51 (8): 553. doi:10.1021/ed051p553.
  3. Brasted, R.; Hirayama, C. (1959). "An Examination of the Absorption Spectra of Some Cobalt(III)-Amine Complexes. Effect of Ligand and Solvents in Absorption". J. Phys. Chem. 63 (6): 780–6. doi:10.1021/j150576a003.
  4. Penland, R.; Lane, T.; Quagliano, J. (1956). "Infrared Absorption Spectra of Inorganic Coordination Complexes. VII. Structural Isomerism of Nitro- and Nitritopentaamminecobalt(III) Chlorides". Journal of the American Chemical Society. 78 (5): 887–9. doi:10.1021/ja01586a001.
  5. Crawford, B.; Talburt, D.; Johnson, D. (1974). "Effects of Cobalt(III) Complexes on Growth and Metabolism of Escherichia coli". Bioinorganic Chemistry. 3 (2): 121–33. doi:10.1016/S0006-3061(00)80035-6.
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