Chloroaquo complexes of titanium(III). The ²T_2g→²E_g absorption band

Abstract

If the chloride ion content of aqueous titanium(III) solutions is gradually increased there is a continuous shifting of the ²T_2g → ²E_g 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⁺}a_w/{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.