Reactive Dimerization of an N-Heterocyclic Plumbylene: C-H Activation with PbII

Abstract

The N-heterocyclic plumbylene [Fe{(η⁵ -C₅ H₄ )NSiMe₃ }₂ Pb:] is in equilibrium with an unprecedented dimer in solution, whose formation involves the cleavage of a strong C-H bond and concomitant formation of a Pb-C and an N-H bond. According to a mechanistic DFT assessment, dimer formation does not involve direct Pb^II insertion into a cyclopentadienyl C-H bond, but is best described as an electrophilic substitution. The bulkier plumbylene [Fe{(η⁵ -C₅ H₄ )NSitBuMe₂ }₂ Pb:] shows no dimerization, but compensates its electrophilicity by the formation of an intramolecular Fe-Pb bond.

Keywords: C−H activation; carbene homologues; lead; metallocenes; subvalent compounds.