Mössbauer spectroscopy of bucky ferrocenes: lattice dynamics and motional anisotropy of the metal atom.

Temperature-dependent (57)Fe Mössbauer effect spectroscopy has been used to elucidate the metal atom dynamics in three neutral and two cationic bucky ferrocenes. For the three diamagnetic complexes Fe(C(60)H(5))Cp (1), Fe(C(60)Me(5))Cp (2), and Fe(C(60)Ph(5))Cp (3), the metal atom motion is anisotropic and the temperature dependence of the mean-square amplitude of vibration of the metal atom at a number of temperatures is reported. The Mössbauer lattice temperatures have been determined and compared to the parent ferrocene (6). The synthesis and X-ray crystal structure of 3 have been determined at 153(2) K, and the (1)H and (13)C NMR spectra have been recorded. The cationic complexes derived from 2 and 3 show spin-lattice relaxation. The relaxation rate appears insensitive to the nearest-neighbor environment of the metal atom in this pair.