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 abstraction from the corresponding dihydridosilane 11 and is further supported by the results of density functional calculations.