CESIUM COBALT DICARBOLLIDE-SOLUBILITY, PRECIPITATION AND REACTIVITY IN BASIC AQUEOUS-SOLUTION

The title compound, Cs+[Co((3)-1,2-C2B9H11)(2)](-) (CsCDC), was precipitated with a NaCDC solution from solutions containing CsCl. The reaction was followed by measuring the loss of light intensity as the precipitate formed. [Cs+] and [CDC-] at the point of precipitation were estimated and approximate values of K-sp for CsCDC were determined at room temperature: 8 x 10(-6) (water), 7 x 10(-6) (1 M NaOH) and 2 x 10(-6) (5M NaCl/0.1 M KOH/1.0 M NaOH). In some cases, NaCDC precipitated from solution when added to the latter salt solution. For the medium, 5 M NaNO3/0.1 M KOH/1.0 M NaOH, a four-fold excess of NaCDC was added to a 10 mM Cs+ solution at 40 degrees C and the [CDC-] measured spectrophotometrically. Only CsCDC precipitated, and a K-sp of 3.9 x 10(-6) was determined. The solubilities of CsCDC were measured in NaNO3 and NaCl solutions at 30 degrees C as a function of the Na salt concentration. The reaction of the CDC- with OH- slowly produces B(OH)(4)(-), H-2 and CoO(OH). The reaction of 22 mu M CsCDC with NaOH (1 M) has a first-order rate constant at 56 degrees C of 8.8 x 10(-7) s(-1), while that for NaCDC (14 mM) is 7.2 x 10(-7) s(-1). The activation energy for the reaction is 110 kJ mol(-1).