From Diaminosilylenes to Silapyramidanes: Making Sense of the Stability of Divalent Silicon Compounds.

Since the discovery of decamethylsilicocene over three decades ago, chemists have successfully isolated a variety of divalent silicon compounds by orchestrating steric and electronic effects to their advantage. Two broad strategies of electronic stabilization appear to have been widely deployed, namely, π-conjugation as in diaminosilylenes and π-complexation as in decamethylsilicocene and silapyramidanes. Herein, we attempted to identify quantitative metrics for the electronic stabilization of silylenes. Singlet-triplet gaps and electron affinities, both physical observables, proved useful in this regard. Thus, the most stable silylenes exhibit unusually large singlet-triplet gaps and very low or negative gas-phase electron affinities. Both metrics signify low electrophilicity, i.e., a low susceptibility to nucleophilic attack. The chemical significance of the ionization potential associated with the Si-based lone pair, on the other hand, remains unclear.

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© 2023 The Authors. Published by American Chemical Society.

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The authors declare no competing financial interest.