Chloroaquo complexes of titanium(III). The 2T2g→2Eg absorption band

Abstract

If the chloride ion content of aqueous titanium(III) solutions is gradually increased there is a continuous shifting of the 2T2g → 2Eg peak from c. 20100 cm-1 to c. 14500 cm-1. By applying the rule of average environment it is possible to draw a ?formation curve? for the number of chloride ions complexed to the central titanium(III) ion and hence to determine the equilibrium constants of the successive chloroaquo complexes as chloride ion replaces water in the octahedral environment. Of these, the first, K1 = {Ti(H2O)5Cl2+}aw/{Ti(H2O)3/6+}{Cl-}, was determined to be 0.07-0.2. The reflectance spectra of purple titanium trichloride hexahydrate (TiCl3,6H2O) and a 5% solution of a-titanium trichloride in KCl-LiCl eutectic mixture at 25� are shown to give ligand field bands in agreement with the above range of wave numbers.