Recent Advances in Silylene Chemistry: Small Molecule Activation En-Route Towards Metal-Free Catalysis

Abstract

Previously only known as fleeting, transient laboratory curiosities in the 1960s, silylenes (species of the general type: SiIIR′R″ where R′ and R″ are any σ or π-bonded substituents, homo or heteroleptic) are now one of the most rigorously investigated classes of compounds in contemporary chemistry. The breakthroughs came in 1986 when Jutzi and co-workers isolated Cp* 2Si: (Cp* = η5-C5Me5), the first isolable Si(II) compound, and later in 1994 with the discovery of the first N-heterocyclic silylene by West and Denk, heralding the beginning of a bourgeoning era in low-valent silicon chemistry. Since these and other key discoveries, massive advances have been made in understanding and elucidating the nature of these reactive compounds, and their ability, for example, to activate small molecules, or behave as ligands in transition metal complexes which can perform a variety of catalytic or stoichiometric transformations. In this chapter, recent advances in silylene chemistry will be presented, with a particular focus on developments in the last 10 years approximately. A key emphasis will rest on the reactivity of isolable silylenes, including their coordination towards metals, with respect to small molecule bond activation, and potential catalytic transformations. Although metal-coordinated silylene complexes have been shown to be catalytically useful in a variety of transformations, metal-free catalysis with silylenes is still a target.