Where silylene-silicon centres matter in the activation of small molecules

Small molecules such as H-2, N-2, CO, NH3, O(2)are ubiquitous stable species and their activation and role in the formation of value-added products are of fundamental importance in nature and industry. The last few decades have witnessed significant advances in the chemistry of heavy low-coordinate main-group elements, with a plethora of newly synthesised functional compounds, behaving like transition-metal complexes with respect to facile activation of such small molecules. Among them, silylenes have received particular attention in this vivid area of research showing even metal-free bond activation and catalysis. Recent striking discoveries in the chemistry of silylenes take advantage of narrow HOMO-LUMO energy gap and Lewis acid-base bifunctionality of divalent Si centres. The review is devoted to recent advances of using isolable silylenes and corresponding silylene-metal complexes for the activation of fundamental but inert molecules such as H-2, COx, N2O, O-2, H2O, NH3, C(2)H(4)and E-4(E = P, As).