What is it about?
This study investigates the low-temperature (-90 °C) ozonolysis mechanism of tris(trimethylsilyl)silane and its monodeuterated analog. By combining experimental product identification (NMR and mass spectrometry) with quantum chemical modeling (M06-2X/MG3S and B3LYP/6-31+G(2d,p)) and primary kinetic isotope effect measurements (kH/kD = 5.5), we determined the precise reaction pathway. The reaction yields tris(trimethylsilyl)silanol and 1,1,1-trimethyl-2,2-bis(trimethylsiloxy)disilan-2-ol.
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Why is it important?
Although silyl hydrotrioxides have been studied for over 50 years as key intermediates in silane ozonolysis and valuable sources of singlet oxygen, the exact mechanism of Si–H bond cleavage by ozone has remained controversial. Our experimental and theoretical results unambiguously prove that the reaction proceeds via hydrogen atom abstraction from the Si–H bond to form a silyl/hydrotrioxide radical pair, rather than direct ozone insertion or ionic pathways. This provides long-sought mechanistic clarity for organosilicon chemistry and selective oxidation processes.
Perspectives
Combining low-temperature kinetic isotope effect measurements with quantum chemical calculations proved to be a decisive approach for resolving a fundamental question in organosilicon chemistry. Uncovering that hydrogen abstraction triggers the formation of an unstable hydrotrioxide intermediate, which subsequently undergoes radical recombination and rearrangement, provides a solid foundation for designing controlled oxidation reactions and efficient singlet oxygen generators for organic synthesis.
Dr Stanislav A. Grabovskii
Ufa Institute of Chemistry of the RAS
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This page is a summary of: Mechanism of the Reaction of Tris(trimethylsilyl)silane with Ozone, Russian Journal of General Chemistry, August 2022, Pleiades Publishing Ltd,
DOI: 10.1134/s1070363222080114.
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