Lattice dynamics of the two distinct Fe atoms in Ar(dppe)FeGaFe(CO)4 (Ar = Cp and Cp∗)

The hyperfine interactions and lattice dynamics of the two Fe atoms in the title compounds have been elucidated using temperature-dependent 57Fe Mössbauer effect spectroscopy (MES). The two Fe atoms are distinct both with respect to the isomeric shift (IS) and quadrupole (QS) hyperfine interactions. The vibrational amplitudes of the metal atoms have been determined by MES and are compared to the corresponding values deduced from single crystal X-ray data at 150 K. The motional anisotropy of the Fe atom ligated to the four CO groups has been determined over the range 90 < T < 342 K, whereas the motion of the Fe atom ligated to the Cp∗ group is effectively isotropic.