STUDIES OF THE BONDING IN IRON(II) CYCLOPENTADIENYL AND ARENE SANDWICH COMPOUNDS .2. CORRELATIONS AND INTERPRETATIONS OF C-13 AND FE-57 NUCLEAR-MAGNETIC-RESONANCE AND FE-57 MOSSBAUER DATA

Carbon-13 NMR data for [Fe(eta-C5H5) (eta-C5H4X)] and [Fe(eta-C5H5) (eta-C6H5X)]+ and Fe-57 NMR data for neutral substituted ferrocenes, ferrocenyl carbenium ions and ferrocenophanes have been analysed and correlations between these data sets and those of the Fe-57 Mossbauer quadrupole splitting (q.s.) are discussed on the basis of concepts put forward previously. For substituted neutral ferrocenes there is a linear relationship between q.s. and chemical shift delta(Fe-57). For ferrocenyl carbenium ions the relationship suggests a change in structure and bonding from species like [Fe(eta-C5H4)(eta-C5H4CMe2)] to the more fulvenoid structure [Fe(eta-C5H5)(C5H4CH2)]+. Bridged ferrocenes (ferrocenophanes) show effects which are associated with ring tilting.