Room-Temperature Synthesis of (LiMo₃Se₃)_n and the Determination of the Relative Reduction Potential of tert-Butyllithium

A room-temperature synthesis of the inorganic polymer (LiMo₃Se₃)_n by reductive intercalation is described. Instead of the traditional preparation by ion exchange at approximately 460 °C, (LiMo₃Se₃)_n was prepared by treating (InMo₃Se₃)_n with a 10-fold excess of tert-butyllithium in pentane/toluene at 23 °C for 1 week. While there is some reductive attack of the (Mo₃Se₃^-)_n chain core, reductive intercalation of lithium competed successfully to form (LiMo₃Se₃)_n, as confirmed by X-ray powder diffraction, TEM, SEM microprobe, and product solubility in polar solvents. Proton NMR spectroscopy was used to confirm that tert-butyllithium reacts by a radical disproportionation process, providing lithium atoms that diffuse into the interstitial spaces of the inorganic polymer matrix. The nonreversible reduction potential of tert-butyllithium was estimated at 0.83 V above Li/Li⁺ by preparation of the reference solid Li_0.37WO₂. Knowledge of this potential has allowed us to assign tert-butyllithium a relative position within the relative hierarchy of organolithium reagents commonly used in the reductive intercalation of solids.