Unraveling the reaction pathways of cyclotrisilenes: a computational analysis

Cyclotrisilenes can pursue four types of reaction pathways with unsaturated substrates: π -addition, σ -insertion, exocyclic σ -insertion, and ring-opening reactions. A computational investigation of all these reaction pathways of 1,2,3,3-tetramethyl cyclotrisilene c-Si 3 Me 4 ( I ) and 1,2-bis(trimethylsilyl)-3,3-dimethyl cyclotrisilene c-Si 3 Me 2 (SiMe 3 ) 2 ( II ) with phenylacetylene ( R1 ) and benzaldehyde ( R2 ) is carried out. The reaction pathways are found to be significantly influenced by the substituents attached to the cyclotrisilene ring. Both the π -addition and the σ -insertion reactions proceed with moderate activation energy and high exoergicity, and the electronic nature of the functional group is crucial in deciding the favorable pathway. The exocyclic σ -insertion reactions are found to possess a huge energy barrier, irrespective of the steric and electronic nature of cyclotrisilenes and the substrates. While the course of the reaction and the viability of the ring-opening reaction with phenylacetylene are impacted by the nature of cyclotrisilene, the ring-opening reactions of I and II with benzaldehyde are both highly endoergic.