Silicon Carbamates by CO₂ Fixation: Brønsted Acid Labile Precursor of a Lewis Superacid

Treatment of Lewis superacidic Si(catCl)2(MeCN)2 and tetramethylpiperidine (TMP) or hexahydropyrimidopyrimidine (hppH) with CO2 leads to an FLP-type formation of silicon carbamates. The employed Lewis base determines the hapticity at silicon and the reactivity of the carbamates in subsequent transformations. Upon treatment with a Brønsted acid, the carbamates liberate CO2 and reactivate the Lewis superacidic behavior of 1. Hence, the CO2 fixation products serve as valuable surrogates for Si(catCl)2 that circumvent its insolubility in organic solvents. Quantum chemical computations support all of the experimental observations