Variable-temperature diffraction study of the barrier to rotation and zero-point motion in bis(η6-benzene)chromium

The mean squared displacements of the η6-benzene ring in Cr(C6D6)2 have been determined at 10 temperatures; extrapolation of these displacements gives a zero-point energy of 0.89 kJ mol−1. The individual barriers to rotation corresponding to these displacements have been determined and decrease with increasing temperature in accord with expansion of the material.