Solid state NMR and computational studies on cyclopentadienyl lithium

Lithiumcyclopentadienide, previously identified to be an endless polymer in the ligand-free solid state, was investigated by ¹³C- and ⁶Li-CP/MAS NMR spectra, and by B3LYP-GIAO theoretical calculations. By spectra simulation, the axially symmetric ¹³C-shift tensor components were identified to be δ₁₁ = δ₂₂ = 151.5 ppm, δ₃₃ = 15.5 ppm. The ⁶Li-tensor components are δ₁₁ = δ₂₂ = +1.0 ppm, δ₃₃ = -43.0 ppm. This extremely high field component is due to cumulative ring current effects. B3LYP-GIAO/TZVP calculations on the tensor principal components agree remarkably well with the measurements. A new and very simple method of preparing air-sensitive compounds for solid-state NMR analyses is described. Graphical abstract Shielding tensor main components from slow-speed solid state NMR spectra.