Substituent Effects on Mossbauer Spectra

The two metal nuclei that can be studied by Mdssbauer spectroscopy and are relevant to metallocenes are Fe and Sn. Spectra from both nuclei have been used to examine the electronic effects of substitution on metallocenes. 

Representative Fe MOssbauer Data for Ferrocenes and Ferrocenium Salts 

)Ph3H)] form) may be causing this effect. The I.S. in decaphenylferro-cene varies from 0.60 mm/s at 298 K to 0.71 mm/s at 15 K both thermal isomerization and the increase in Fe-ring distance found in the room-temperature structure (see Section IV) may contribute to the high I.S. values. 

Oxidation of ferrocene to the ferrocenium cation almost always results in the collapse of the Q.S. This effect has been related to the redistribution of electron density in the t/-orbitals upon oxidation, which leads to a more symmetrical electric field gradient. Consequently, observed Q.S.s 

Representative Sn Mossbauer Data for Stannocenes AND Related Compounds 

Representative ll9Sn Mossbauer Data for Stannocenes and Related Compounds 

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