Tin–carbon bond formation by simple addition of cyclic dienes to a bis(amino)stannylene: a mechanistic study

Abstract

The addition of cyclopentadiene and indene to Bu^t[graphic omitted]n resulted in the formation of ‘adducts’(X-ray structural characterisation) through tin-carbon bonding and hydrogen migration to one of the nitrogen atoms. In the cyclopentadienyl compound π bonding is observed (Sn–C 2.47–2.76 Å) whereas the indenyl derivative displays a σ-bond (Sn–C 2.343 Å). In a similar reaction of Bu^t[graphic omitted] (E = Ge or Pb) with cyclopentadiene either the starting compounds or plumbocene along with an amine were isolated. At room temperature the reaction between indene and the cyclic stannylene is an equilibrium, the rate constants of which were raised by a factor of 3.0 for the association and slowed by a factor of 4.2 for the dissociation when deuteriated indene was used. From the kinetic data, a concerted addition mechanism of the proton and the indenyl group is favoured over an ionic two-step mechanism. If the steric hindrance of the protic cyclic diene system is raised (pentamethylcyclopentadiene) no reaction between the stannylene and diene is observed.