Hexaamminecobalt(III) chloride is a component of structural biology methods, especially for DNA or RNA, where the positive ions stabilize the tertiary structure of the phosphate backbone, which favors to solve their structure by X-ray crystallography. It serves as an excellent antibacterial and antiviral property.
As reagent for pyrophosphoric acid, for the estimation of phosphate.
Synthesis of hexaamminecobalt(III) chloride
2CoCl2+10NH3+2NH4Cl+H2O2 →2[Co(NH3) 6]Cl3+2H2O
Reaction. Dissolve 2.5 g (10.5 mmol) of cobalt(II) chloride hexahydrate and 1.7 g (32 mmol) of ammonium chloride (about 195% excess) in 15 mL of distilled water. Add 0.5 g of activated charcoal and 23 mL (380 mmol) of concentrated aqueous ammonia (about 624% excess). Cool the reaction mixture to 0 oC in an ice bath. Slowly add 2 mL (19.5 mmol) of 30% hydrogen peroxide (about 271% excess), with stirring – maintain the temperature below 10°C. After the hydrogen peroxide has been added, heat the reaction mixture to 60°C for about 30 minutes. Cool the reaction mixture to 0 oC to cause precipitation of the product.
Hexammine cobalt(III) is considered an analog of fully solvated magnesium, capable of activating some enzymes that requires magnesium. It is useful in DNA condensation studies.
It crystallises from warm water (8mL/g) on cooling. [Bjerrum & McReynolds Inorg Synth II 217 1946.]
