CeCl₃ /n-BuLi: Unraveling Imamoto's Organocerium Reagent

CeCl₃ (thf) reacts at low temperatures with MeLi, t-BuLi, and n-BuLi to isolable organocerium complexes. Solvent-dependent extensive n-BuLi dissociation is revealed by ⁷ Li NMR spectroscopy, suggesting "Ce(n-Bu)₃ (thf)_x " or solvent-separated ion pairs like "[Li(thf)₄ ][Ce(n-Bu)₄ (thf)_y ]" as the dominant species of the Imamoto reagent. The stability of complexes Li₃ Ln(n-Bu)₆ (thf)₄ increases markedly with decreasing Ln^III size. Closer inspection of the solution behavior of crystalline Li₃ Lu(n-Bu)₆ (thf)₄ and mixtures of LuCl₃ (thf)₂ /n-BuLi in THF indicates occurring n-BuLi dissociation only at molar ratios of <1:3. n-BuLi-depleted complex LiLu(n-Bu)₃ Cl(tmeda)₂ was obtained by treatment of Li₂ Lu(n-Bu)₅ (tmeda)₂ with ClSiMe₃ , at the expense of LiCl incorporation. Imamoto's ketone/tertiary alcohol transformation was examined with 1,3-diphenylpropan-2-one, affording 99 % of alcohol.