Bonding, Hyperfine Interactions, and Lattice Dynamics of Cationic and Neutral Ferrocenyl-Substituted Allylic and Cumulenic Compounds.

The synthesis and spectroscopic characterization (by mass, UV-visible, IR, NMR and (57)Fe Mössbauer spectroscopy) of three new compounds related to seven recently published ferrocenyl-substituted allylic and cumulenic compounds are reported and have made it possible to effect a systematic evaluation of the parameters extractable from temperature-dependent gamma ray resonance studies. For the neutral species, the hyperfine parameters (IS and QS) of the sigma-bonded ferrocenyl groups are insensitive to the structural details of the allylic or cumulenic carbon framework. The temperature dependence of the recoil-free fraction is dominated by the Cp ring-iron atom interaction, and is not diagnostic of the detailed molecular architecture. In the case of the carbocationic complexes, two distinct iron sites are resolvable from the Mössbauer data. The detailed temperature-dependent behavior of the hyperfine parameters and recoil-free fraction for 10 complexes with either equivalent termini, linked by similar, but different types of bridges (neutral 1-5), or with inequivalent moieties linked by related or identical connectors (cationic 6-10), has been elucidated over the temperature range 90