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Selective activation of small molecules by using non- and semi-metals instead of expensive and toxic precious metals is a contemporary challenge in catalysis. Recently, we developed the zwitterionic silylene 1 which shows an unprecedented reactivity pattern with respect to small molecule activation based on divalent silicon. Silylene 1 is a stronger sigma-donor ligand towards transition-metals than N-heterocyclic carbenes (NHCs) and phosphines and enables unique catalytic transformations involving cooperative ligand-metal effects. Likewise, the chelate silylene-carbene ligand 2, which is accessible by the reaction of 1 with the corresponding NHC, exhibits superior catalytic performance in various metal-mediated catalytic transformations. Furthermore, the remarkably rich reactivity pattern of 1 and the first bis(silylene)-based pincer arene ligands 4-7 can be used as a new generation of powerful steering ligands in homogeneous catalysis. I wish to discuss a few unique features of these N-heterocyclic silylenes in metal-free and non-precious metal-mediated stoichiometric and catalytic transformations. |