Dihydrogen Activation by a Silylium Silylene Frustrated Lewis Pair and the Unexpected Isomerization Reaction of a Protonated Silylene

The isolable silylene 1 forms a frustrated Lewis pair with silylium ion 2 that is able to split hydrogen under ambient conditions. The protonated silylene 3 obtained in this reaction isomerizes to yield the hydrogen‐bridged disilyl cation 4. Cation 4 is fully characterized by NMR spectroscopy and by XRD analysis. Its formation via the protonated silylene 3 is indicated by independent synthesis of cation 3 by hydride ion from the corresponding dihydridosilane 11 and is further supported by the results of density functional calculations. Low coordinated silicon: The frustrated Lewis pair (FLP) formed from an isolable silylene and silylium ion activates dihydrogen (see scheme). In an unexpected follow‐up reaction the silyl cation with a Si–H–Si linkage is formed.