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)(3)S](+) 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)(3)S](+) cation as the final product, crystal structures of [(Et3Si)(2)SMe](+), [Et3SiS(H)Me](+), and [Et3SiOC(H)OSiEt3](+) were obtained. Experimental results combined with supporting quantumchemical calculations in the gas phase and solution allow a detailed understanding of the reaction cascade.