Redox Cycling at Tellurium: Selective and Multiple Activation of Si─H Bonds in Common Organosilanes and SiH₄

Redox catalysis involving the tellurenyl triflate [2-(tBuNCH)C₆H₄Te][OTf] was utilized for the activation of the common silanes Et₃SiH, Ph_{4- n}SiH_n (n = 1-3) as well as the difficult-to-handle gaseous SiH₄. Furthermore, complex siloxanes containing multiple Si─H bonds were converted into siloxylated phenols, which are of high interest for the chemical industry. Insights into the catalytic cycle utilizing para-quinones as both oxidants and substrates were provided by identification of key intermediates and by using in situ time-resolved FTIR spectroscopy, NMR spectroscopy, single-crystal X-ray diffraction analysis, and DFT calculations. Based on this study, the catalytic cycle is initiated by a Si─H bond activation resulting in the formation of a ditelluride species and the corresponding silyl triflate. In turn, the ditelluride species is first oxidized by the presented quinone, forming an unprecedented tellurium-based oxonium intermediate, resulting in the formation of the siloxylated phenols and liberation of the tellurium catalyst upon subsequent reaction with the silyl triflate. Our proposed catalytic cycle can be generalized for any silane used in this study.