Activation of CS2 and CO2 by Silylium Cations.

The hydride‐bridged silylium cation [Et3Si−H−SiEt3]+, stabilized by the weakly coordinating [Me3NB12Cl11]− anion, undergoes, in the presence of excess silane, a series of unexpected consecutive reactions with the valence‐isoelectronic molecules CS2 and CO2. The final products of the reaction with CS2 are methane and the previously unknown [(Et3Si)3S]+ cation. To gain insight into the entire reaction cascade, numerous experiments with varying conditions were performed, intermediate products were intercepted, and their structures were determined by X‐ray crystallography. Besides the [(Et3Si)3S]+ cation as the final product, crystal structures of [(Et3Si)2SMe]+, [Et3SiS(H)Me]+, and [Et3SiOC(H)OSiEt3]+ were obtained. Experimental results combined with supporting quantum‐chemical calculations in the gas phase and solution allow a detailed understanding of the reaction cascade. [ABSTRACT FROM AUTHOR]