Generation, bonding and reactivity of transient zinc-substituted silylenes

The metal-substituted silylenes are of high interest, as the theoretical studies indicated that the silylenes with electropositive substituents have a small ΔE_S−T (singlet-triplet energy gap) or even the ground-state triplets. However, such compounds are highly unstable, and only two transient alkali metal-substituted silylenes M(^tBu₃Si)Si: (M = Li, K) were generated by photoextrusion of the alkali metal-substituted silacyclopropenes and merely studied by spectroscopic method (EPR) at low temperature (14 to 50 K). Herein, we report the generation of transient zinc-substituted silylenes from zinc silacyclopropanyl complexes under very mild and convenient conditions. The generated transient zinc-substituted silylenes are highly reactive and undergo intermolecular cycloaddition with alkenes for the synthesis of zinc-substituted Si-heterocyclic compounds. If there is no substrate, the zinc-substituted silylenes attack the C-C bonds of the β-diketiminato ligands and break the C-C bonds. DFT studies further highlight the silylene nature of the zinc-substituted silylene and a very small ΔE_S−T (4.4 kcal/mol).