Isolable silylenes and their diverse reactivity

A considerable number of isolable silylenes, silicon divalent compounds, have been synthesized and great efforts have been made of the discovery of their distinctive structural and physical properties and their characteristic reactions over the last three decades. While many reviews have been published on the isolable silylenes until now, the present review uniquely focuses on the differences in the properties and reactivities among the known stable silylenes including those dialkyl-, diamino-and amino(alkyl)silylenes that are sterically and/or electronically stabilized. Some extra-coordinated silylenes reported are discussed subsidiarily. In a brief introduction are discussed the remarkable substituent effects on the Si-29 NMR chemical shift of the silylene silicon nucleus, the UV-vis absorption maxima and MO properties revealed by the DFT calculations. Then, the diverse reactions of the silylenes reported, their mechanisms, and the substituent effects on the reactivity are discussed. The reactions of the silylenes surveyed here are those with (i) sigma bonds like X-H (X = H, C, O, N, Si, etc.), C-Cl, Si-Cl, etc., (ii) unsaturated pi bonds like C=C, C=O, C=N, N=N, C=N, etc., (iii) alkali metals affording the corresponding radical anions via one-electron transfer, and (iv) transition metal complexes of copper, silver, nickel, palladium and platinum. (c) 2022 Elsevier B.V. All rights reserved.

Automated summary

In the past three decades, a significant number of isolable silylenes have been synthesized and studied for their unique properties and characteristic reactions. This review focuses on the differences in properties and reactivities among stable silylenes and includes discussion of some extra-coordinated silylenes. The review covers substituent effects on Si-29 NMR chemical shift, UV-vis absorption maxima, MO properties, as well as diverse reactions and mechanisms of silylenes.