Activation of Allenes by Diferrocenylphosphenium Ion: Isolation of a Wheland Intermediate of Ferrocene

Abstract

The reaction of the diferrocenylphosphenium ion with four terminal allenes follows two different pathways, via allyl or vinyl carbocations, which proceed with electrophilic substitution reactions at one ferrocenyl moiety to form persistent Wheland intermediates and eventually alkenyldiferrocenylphosphonium salts. The reaction of the diferrocenylphosphenium ion with 2-(trimethylsilyl)-2,3-pentadiene affords a stable Wheland intermediate of ferrocene in high yields, which is isolated and fully characterized.