A Stable Silanone with a Three-Coordinate Silicon Atom: A Century-Long Wait is Over

摘要

Silanones (R2Si=O), the silicon analogues of ketones, are one of the most sought-after compounds in main-group chemistry. More than 100 years ago, Kipping and Lloyd first attempted to synthesize silanones, although physical and chemical studies showed that they did not obtain silanones, but single-bonded siloxanes, (R2SiO)_n. Unlike ketones, silanones are extremely reactive, and this enhanced reactivity stems from 1) a weak π-bond with a small HOMO-LUMO energy gap that is due to unfavorable overlapping between the p_π(Si) and p_π(O) orbitals and 2) a strongly polarized Si~(5+)-O~(δ-) bond. As a result, the Si=O bond has an extreme propensity towards oligomerization even under ambient conditions. Until very recently, the Si=O bond had only been detected either in the gas phase or in an argon matrix at 77 K, and the presence of such species as intermediates had been confirmed by trapping reactions or kinetic studies. However, the isolation and characterization of a species with a Si=O double bond ("Kipping's Dream") had not been reported.