Lattice dynamics and hyperfine interactions of C₆₀Fe(CO)₄

Detailed ⁵⁷Fe Mossbauer experiments over the range 85<T<210 K have been carried out on the tetra-carbonyl iron derivative of C₆₀(I) as well as on several related organometallic solids. The observed isomer shift and quadrupole splitting parameters are consistent with a bonding interaction between the metal center and the ligand which involves a single carbon-carbon double bond of the buckminsterfullerene. The temperature dependence of the recoil-free fraction, compared to analogous data for maleic anhydride Fe(CO)4(II), suggests that the two previously observed low frequency lattice modes in C₆₀ persist in I. Contrary to expectations, there is no significant temperature-dependent vibrational anisotropy (Gol'danskii-Karyagin effect) evident in the above temperature range.