Electronic effects in metallocenes

• Published in: Journal of organometallic chemistry Vol. 39; no. 1; pp. 173 - 177
• Main Authors: Nesmeyanov, A.N., Kochetkova, N.S., Leonova, E.V., Fedin, E.I., Petrovskii, P.V.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.1972
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/S0022-328X(00)88917-2

A comparative study of the PMR spectra of isoelectronic ferrocene and cobalticinium salt homologues has been undertaken. With cobalticinium salts the introduction of a positive charge leads to a decrease in the ring proton shielding, while the introduction of alkyl groups has a similar effect on the electronic structure of both the cobalticinium cation and ferrocene. It was found that the introduction of primary and secondary alkyl groups caused proton signal shifts not only in those rings which were directly substituted but also in unsubstituted metallocene rings. However, within the experimental accuracy of the method it was found that the tertiary butyl group has no influence on the proton chemical shifts in the free cyclopentadienyl ring. These results, as well as other chemical data, are explained by assuming that the heteroannular action of aliphatic substituents upon a metallocene system is generally controlled by resonance effects introduced by these groups.