Disordered crystal structure of pentamethylcyclopentadienylsodium as seen by high-resolution X-ray powder diffraction

The crystal structure of pentamethylcyclopentadienylsodium, [NaC10H15] (NaC p*), has been determined from high-resolution X-ray powder diffraction. The compound crystallizes in space group Cmcm with lattice parameters a = 4.61 030 (3), b = 16.4621 (3), c = 14.6751 (2) Angstrom, V = 1113.77 (4) Angstro m (3) (Z = 4). NaCp* forms polymeric multidecker chains along the a axis. T he Rietveld refinement (R-p = 0.050 and R-F = 0.163) shows that the Cp* moi eties occupy, with disorder, two different orientations rotated away from t he eclipsed conformation by +/- 13.8 degrees.