Carbonium Ion Stabilization by Metallocene Nuclei. II. α-Metallocenylcarbonium Ions

Abstract

Acetates of methylferrocenylcarbinol, methylruthenocenylcarbinol and methylosmocenylcarbinol have been found to solvolyze with rates somewhat greater than trityl acetate, indicating a high stability for the corresponding carbomum ions. The solvolysis mechanism for methylferrocenylcarbinyl acetate has been carefully investigated to show that a carbonium ion mechanism is involved. Several possibilities for a molecular orbital description of direct metal participation are discussed. The order for carbonium ion stabilization (osmocenyl > ruthenocenyl > ferrocenyl) is found to parallel that of the strength of intramolecular hydrogen bonds to the carbinols, but is the reverse of that observed for reactivity of the parent metallocene toward acetylation.

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