Phosphination of ferrocenium cation with aminophosphines

Abstract

Ferrocenium hexafluorophosphate reacts with aminophosphines P(NEt₂)₃, PhP(NEt₂)₂, Ph₂P(NEt₂), CyP(NEt₂)₂, and Prⁱ₂P(NEt₂) to form ferrocenylphosphonium salts [(C₅H₅)-Fe(C₅H₄PRR′R″)](PF₆), ferrocene, and [HPRR′R″](PF₆). The theoretical analysis of the reactions (M06-L/6-311++G(d,p)) showed that these reactions involve a sequence of the following steps: the addition of phosphine to the cyclopentadienyl ring, the oxidation of the initial adduct by the starting ferrocenium to give a dicationic η⁴-phosphocyclopentadiene complex with an agostic \(C_{sp^{3}}-H\rightarrow{Fe}\) bond, and the deprotonation of this bond to form ferrocenylphosphonium salts. The resulting ferrocenylphosphonium salts are resistant to alcoholysis and do not react with carbon disulfide.