Determination of the structural formula of sodium tris-carbonatocobaltate(III), Na3[Co(CO3)3]·3H2O by thermogravimetry

The existence of an inner sphere water in sodium tris-carbonatocobaltate(III) prepared by the Bauer and Drinkard method was confirmed by thermogravimetry, which led to its formulation as sodium aquo-tris-carbonatocobaltate(III) dihydrate, Na3[Co(H2O)(CO3)3]·2H2O. Hydrolytic study on 4-nitrophenylphosphate promoted by [Co(tn)3]3+ afforded corborating evidence for the existence of inner sphere water in the complex leading to its formulation as [Co(tn)3(H2O)]3+. Another variety of the tris-carbonato anion, [Co(NH3)6][Co(CO3)3], was prepared and subjected to thermogravimetric analysis, and the absence of inner sphere water in the compound was confirmed. The plausible existence of inner sphere water for the compounds that emanate from the synthetic routes utilizing the Bauer and Drinkard method in the crystalline phase is proposed.