Stimuli Responsive Silylene: Electromerism Induced Reversible Switching Between Mono‐ and Bis‐Silylene

Electromerism is a very well‐known phenomenon in transition metal chemistry. In main group chemistry, this concept has only started getting attention recently. We report stimuli responsive low‐valent silicon compounds exhibiting electromerism. A mixed‐valent silaiminyl‐silylene 1, [LSi−Si(NDipp)L] (L=PhC(N( t )Bu)(2)), was synthesized in a single step from amidinate‐chlorosilylene. Compound 1 has two interconnected Si atoms in formally +I and +III oxidation states. Upon treatment with Lewis acidic Cu(I)X (X=mesityl, Cl, Br, I), electron redistribution occurs resulting in the formation of [{LSi(NDipp)Si(L)}−CuX], in which both silicon atoms are in the +II formal oxidation state. Removal of the copper center from [{LSi(NDipp)Si(L)}−CuX] by using a Lewis basic carbene led to reformation of the precursor [LSi−Si(NDipp)L]. Thus, the process is fully reversible. This showcases the first example of Lewis acid/base‐induced reversible electromerism in silicon chemistry.