Gas-Phase Preparation of Silyl Cyanide (SiH3CN) via a Radical Substitution Mechanism

• Published in: Journal of the American Chemical Society 2022-05, Vol.144 (19), p.8649-8657
• Main Authors: Yang, Zhenghai, He, Chao, Goettl, Shane J., Paul, Dababrata, Kaiser, Ralf I., Silva, Mateus X., Galvão, Breno R. L.
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.2c01349

The silyl cyanide (SiH3CN) molecule, the simplest representative of a fully saturated silacyanide, was prepared in the gas phase under single-collision conditions via a radical substitution mechanism. The chemical dynamics were direct and revealed a pronounced backward scattering as a consequence of a transition state with a pentacoordinated silicon atom and almost colinear geometry of the attacking cyano radical and leaving hydrogen. Compared to the isovalent cyano (CN)–methane (CH4) system, the CN–SiH4 system dramatically reduces the energy of the transition state to silyl cyanide by nearly 100 kJ mol–1, which reveals a profound effect on the chemical bonding and reaction mechanism. In extreme high-temperature environments including circumstellar envelopes of IRC +10216, this versatile radical substitution mechanism may synthesize organosilicon molecules via reactions of silane with doublet radicals. Overall, this study provides rare insights into the exotic reaction mechanisms of main-group XIV elements in extreme environments and affords deeper insights into fundamental molecular mass growth processes involving silicon in our universe.