Evidence for Rh(II) in a LiCl-KCl eutectic. An optical absorption investigation

Rhodium exists in LiCl-KCl melts at 400–450°C as the RhCl63− species. Spectroscopic data show that an increase of the temperature up to 600°C leads to a reaction of this species with the melt and to the formation of the stable (Rh(II) chlorocomplex. This reaction, which has not been reported previously, is reversible since on cooling to lower temperatures, 400–450°C, reoxidation to the Rh(III) complex is observed. The Rh(II) complex however persists even at these lower temperatures if the experimental cell is connected to a vacuum line to remoe the chlorine formed in the reduction reaction.