Cofacial interaction of ferrocenyl groups and metal atom motional anisotropy in [10]annulene organometallics

Two structurally related diferrocenyl [10]annulenes have been examined over the range 90≤T≤370 K by temperature dependent 57Fe Mössbauer effect (ME) spectroscopy. While the hyperfine interaction parameters [isomer shift (IS) and quadrupole splitting (QS)], and their temperature dependencies are very similar to those which have been reported earlier for similar ferrocenyl complexes, the vibrational anisotropy of the iron atom motion is diagnostic of a cofacial interaction of the two cyclopentadienyl rings in the 2,10-diferrocenyl compound, and absent in the 2,7-diferrocenyl homologue. These results are compared with the corresponding behavior of the 1,5- and 1,8-diferrocenylnaphthalene compounds reported earlier.