NMR Study of Ferrocene, Ruthenocene, and Titanocene Dichloride

The line widths of the proton magnetic resonance absorption spectra and the spin-lattice relaxation times for polycrystalline samples of ferrocene, ruthenocene, and titanocene dichloride were measured as functions of temperature, and are interpreted in terms of reorientation of the cyclopentadienyl rings about their fivefold axes. At low temperatures such reorientation is interpretable in terms of an activated process governed by a single correlation time, and the barrier restricting reorientation is obtained. At higher temperatures for these substances, as well as for benzene, such an interpretation is not suitable, and a hypothesis involving the coupling and uncoupling of adjacent rings taking part in reorientation is proposed to account for the data.