Substituent effects at silicon in cations SiX+, HSiX+•, and H2SiX+, and in radicals H2SiX+•
- 1 June 1989
- journal article
- Published by Canadian Science Publishing in Canadian Journal of Chemistry
- Vol. 67 (6) , 991-997
- https://doi.org/10.1139/v89-151
Abstract
Abinitio molecular orbital calculations at the 6-31G* level have been used to optimise structures for ions SiX+, HSiX+•, and H2SiX+, and for neutrals HSiX (singlets), H2SiX•, and H3SiX, where X is H, CH3, NH2, OH, F, CN, and NC. Single point calculations at the MP4(SDTQ)/6-31G* level were used to calculate substituent stabilisation energies.The amino group is the strongest π-donor and also is the most stabilising group in the cations, the silylenes, and the silyl radicals. Stabilisation is greatest in ions SiX+. Ions HSiX+• and H2SiX+ are stabilised by similar but smaller amounts, although CN and NC are destabilising in these ions. Substituent stabilisation energies in radicals H2SiX• are almost zero. There is a linear relationship between the stabilisation energies of ions H2SiX+ and the ionisation potentials of radicals H2SiX•, but a similar plot correlating stabilisation energies for ions HSiX+۟• with the ionisation potential of HSiX (singlet) shows considerable scatter. Keywords: silications, silyl radicals, stabilisation energies.Keywords
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