Carbonatobis(ethylenediamine)cobalt(III) chloride is a salt with the formula [CoCO<sub>3</sub>(en)<sub>2</sub>]Cl (en = ethylenediamine). It is a red diamagnetic solid that is soluble in water. It is the monochloride salt of a cationic carbonate complex [CoCO<sub>3</sub>(en)<sub>2</sub>]+. The chloride ion in this salt readily undergoes ion exchange. The compound is synthesized by the oxidation of a mixture of cobalt(II) chloride, lithium hydroxide, and ethylenediamine in the presence of carbon dioxide:[1]
CoCl2 + 2 en + CO2 + 0.5H2O2 + LiOH → [CoCO<sub>3</sub>(en)<sub>2</sub>]Cl + H2O + LiCl
The cationic complex is octahedral with C2 symmetry.[2]
The carbonato ligand is readily replaced upon acid hydrolysis. Derivatives include the following complexes: cis- and trans-[CoCl<sub>2</sub>(en)<sub>2</sub>]+, cis-[Co(OH)(H<sub>2</sub>O)<sub>3</sub>(en)<sub>2</sub>]2+, cis-[Co(OH<sub>2</sub>)<sub>2</sub>(en)<sub>2</sub>]+, and cis-[Co(NO<sub>2</sub>)<sub>2</sub>(en)<sub>2</sub>]+.[1] Reaction with trifluoromethanesulfonic acid (HOTf) gives [Co(OTf)<sub>2</sub>(en)<sub>2</sub>]OTf.[3]