Scheme 6. Reaction of 1H2 with Li[HBEt3] at –30 °C to give Li[10], which isomerizes to Li[7] at room temperature (top). Compound Li2[11] forms in both reactions, tBuCCLi/Li[1H] and tBuCCH/Li2[1] (bottom; carbon atoms marked with asterisks bear tBu substituents). Molecular structure of [Li(12-crown-4)(thf)][Li(thf)2][11] in the solid state. The solvent-separated cations, phenyl-bonded tBu groups, and all CH atoms are omitted for clarity.
