Polarography in Acetonitrile of Titanium Tetrachloride and Tetraiodide in Various Supporting Electrolytes

Abstract

Current‐potential curves of titanium tetrachloride in acetonitrile (AN) with tetraethylammonium perchlorate as supporting electrolyte have been determined at the dropping mercury electrode. The effect of chloride, bromide, iodide, and thiocyanate ions has been investigated. In general, only two well defined reduction waves were obtained corresponding to the reduction of Ti(IV) to Ti(III) and Ti(0), respectively. With tetraethylammonium chloride as supporting electrolyte, three reduction waves corresponding to the reduction of Ti(IV) to Ti(III), Ti(II), and Ti(0), respectively, were observed. The valence states of these reduced titanium species was verified by constant potential electrolysis experiments. Titanium tetrachloride in AN reacts with mercury to produce mercurous chloride and Ti(III). The latter reacts slowly with perchlorate if present. No reaction with mercury occurs in the presence of excess chloride ions, or if the water content is 0.03M or greater. Water at this concentration slowly hydrolyzes titanium tetrachloride in AN. Titanium tetrachloride is strongly solvated in AN and conductance data indicate that the solvate dissociates according to with a dissociation constant of . Titanium tetraiodide in AN with tetraethylammonium perchlorate as supporting electrolyte gives a single reduction wave at the dropping mercury electrode corresponding to the reduction of Ti(IV) to Ti(0). In the presence of excess chloride ions replacement of the iodide occurs and three reduction waves are observed, similar to those obtained with titanium tetrachloride. Solutions of titanium tetraiodide in AN are extremely sensitive to traces of oxygen, except in the presence of excess chloride ions.