Room-Temperature-Observable Interconversion Between Si(IV) and Si(II) via Reversible Intramolecular Insertion Into an Aromatic C-C Bond

An easily isolable silacycloheptatriene (silepin) 1 b was synthesized from the reaction of a N-heterocyclic imino (IPrN) substituted tribromosilane IPrNSiBr3 with the sterically congested bis(trimethylsilyl)triisopropylsilyl silanide KSi(TMS)(2)Si(Pr-i)(3) (BTTPS). In solution, the Si(IV) silepin 1 b is in a thermodynamic equilibrium with the acyclic Si(II) silylene 1 a. The relative concentration of the Si(II) or Si(IV) isomers can be controlled by temperature variation and observed by variable temperature NMR and UV/Vis spectroscopy. DFT calculations show a small reaction barrier for the Si(II)Si(IV) interconversion and a small energy gap between the Si(II) and Si(IV) species. The reactivity of 1 a/b is demonstrated on a variety of small molecules.

Automated summary

An easily isolable silacycloheptatriene was synthesized and the relative concentration of its isomers was controlled by temperature variation. The reactivity of the compound was demonstrated on small molecules.