Silylenes with a Small Chalcogenide Substituent: Tuning Frontier Orbital Energies from O to Te

The general synthesis of heteroleptic acyclic silylenes with a bulky carbazolyl substituent (dtbpCbz) is detailed and a series of compounds with a chalcogenide substituent of the type [(dtbpCbz)SiE16R] (E16R=OtBu, SEt, SePh, TePh) is reported. With the bulky carbazolyl substituent present, the chalcogenide moiety can be very small, as is shown by incorporating groups as small as ethyl, phenyl or tert‐butyl. For the first time, the electronic properties of the silylene can be tuned along a complete series of chalcogenide substituents. The effects are clearly visible in the NMR and UV/Vis spectra, and were rationalised by DFT computations. The reactivity of the heaviest chalcogenide‐substituted silylenes was probed by reactions with trimethylphosphine selenide and the terphenyl azide TerN3 (Ter=2,6‐dimesitylphenyl). Acyclic dicoordinated silylenes with small chalcogenide substituents were prepared and characterised, enabled by a bulky carbazolyl scaffold. The electronic properties change dramatically from O to Te, with decreasing HOMO–LUMO gaps and increasing chemical shift of the 29Si NMR resonances.