Electron spin resonance studies on titanium(III) chloride in aqueous 2-methyl- 2-butanol (z-amyl alcohol)

Abstract

On addition of small amounts of water (1% to 2%, v/v) to TiCl₃ (0.02 <em>M, p</em>H 1.4 to 1.8) partially dissolved in <em>t</em>-amyl alcohol, an electron spin resonance signal (g₀ = 1.9589 ± 0.0002) with well-resolved superhyperfine structure due to water protons is observed (the coupling constant equals 0.187 ± 0.003 mT). Confirmation of splitting to be due to water hydrogens has been obtained by using D₂O in equivalent experiments. Aqueous solutions of Ti₂(SO₄)₃, TiBr₃ or TiI₃ (0.01 <em>M </em>to 1.0 <em>M, p</em>H 0.8 to 1.8) saturated with <em>t</em>-amyl alcohol (ca. 5%, v/v<em>) </em>give no electron spin resonance signal. Addition of NaCl or LiCl (1.0 <em>M</em>) to these solutions produces a signal identical in hyperfine pattern and-close in the value of <em>g </em>factor (1.9580±0.0002) to that for TiCl₃ solution. It is proposed that there are axial alkoxide and chloride ions and four equatorial water molecules in the first coordination sphere of this ESR-active Ti(III) complex ion. Approximate spin concentration measurements, made employing deuterated samples, indicate that maximum ESR signal intensity (at ca. 2% added water) represents only 15 ± 5% of the nominal Ti(III) that is present.