Activation of CS2 and CO2 by Silylium Cations

The hydride-bridged silylium cation [Et 3 Si-H-SiEt 3 ] + , stabilized by the weakly coordinating [Me 3 NB 12 Cl 11 ] - anion, undergoes, in the presence of excess silane, a series of unexpected consecutive reactions with the valence-isoelectronic molecules CS 2 and CO 2 . The final products of the reaction with CS 2 are methane and the previously unknown [(Et 3 Si) 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 [(Et 3 Si) 3 S] + cation as the final product, crystal structures of [(Et 3 Si) 2 SMe] + , [Et 3 SiS(H)Me] + , and  [Et 3 SiOC(H)OSiEt 3 ] + were obtained. Experimental results combined with supporting quantum-chemical calculations in gas phase and solution allow a detailed understanding of the reaction cascade.