Unidentate-dicarbonato Complexes of Cobalt III

In the following, preparations of cw-diamminedicarbonatocobaltate(III), di-carbonatofl, 2-ethanediamine)cobaltate(III), and c/j-dicarbonatodicyanocobal-tate(III) compounds, all starting from the green solution, are given. Besides the preparations, optical resolutions of these compounds are described. 

Potassium tricarbonatocobaltate(III) is the starting material. The solid potassium tricarbonatocobaltate(III) trihydrate has been isolated,2 but it is very unstable. The complex is stable in water containing potassium hydrogen carbonate, and it is therefore used as a solution containing an excess of potassium hydrogen-carbonate. 

Thirty-five grams (0.35 mole) of potassium hydrogen carbonate is suspended in 20 mL of water, and the slurry is kept in an ice-salt bath. Fifteen grams (0.05 mole) of cobalt(H) nitrate hexahydrate is dissolved in 10 mL of 30% hydrogen peroxide, and the solution is kept in an ice-salt bath. The solution is added dropwise to the ice-cold slurry with stirring. 

H Caution. Add two or three drops at a time. When bubbling stops, again two or three drops are added. This procedure is repeated. Finish adding the whole in about one hour. 

The resulting solution is filtered by suction. The filtrate must be a clear solution and is used immediately as a starting material. 

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