Nitropentaamminecobalt(III) chloride is an

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...

with the molecular formula o(NH₃)₅(NO₂)l₂. 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 transition metal nitrite complex o(NH₃)₅(NO₂)sup>2+.

Linkage isomers

The

coordination complex A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Many ...

es o(NH₃)₅(NO₂)sup>2+ and o(NH₃)₅(ONO)sup>2+ provided an early example of

linkage isomerism In chemistry, linkage isomerism or ambidentate isomerism is a form of isomerism in which certain coordination compounds have the same composition but differ in their metal atom's connectivity to a ligand. Typical ligands that give rise to linkage ...

. This nitritopentaamminecobalt(III) isomer converts to the more stable nitro form at room temperature. 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. 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. The O-linkage isomer scrambles rapidly between the two oxygen sites, i.e. Co-O*NO/Co-ONO*.

Preparation and reactions

Nitritopentaamminecobalt(III) chloride is prepared by treating

chloropentamminecobalt chloride Chloropentamminecobalt chloride is the dichloride salt of the coordination complex o(NH3)5Clsup>2+. It is a red-violet, diamagnetic, water-soluble salt. The compound has been of academic and historical interest. Synthesis and reactions The s ...

with sodium nitrite: : o(NH₃)₅Clsup>2+ + NO₂⁻ → o(NH₃)₅(ONO)sup>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. 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.

References

{{reflist Cobalt complexes Cobalt(III) compounds Ammine complexes Chlorides