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Theoretical study on the α-proton hfs constant in methylsilyl radicals

✍ Scribed by Maurizio Guerra

Publisher
Elsevier Science
Year
1995
Tongue
English
Weight
524 KB
Volume
246
Category
Article
ISSN
0009-2614

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✦ Synopsis

Ab initio UHF/TZP

calculations on the a-methyl substituted silyl radicals H,_,kMe, (n = O-2) show that methyl substitution does not appreciably change the geometry at silicon, which is computed to be nearly tetrahedral, as previously suggested on the basis of the significant variations observed experimentally in the a-proton hyperfine splitting constant, a('H,). UMP2/DZP//TZP calculations reproduce well these variations and show that they are mainly due to spin-polarization effects. The magnitude of a('H,) is, however, slightly underestimated. The agreement improves both by using higher correlated wavefunctions (UQCISD(T)) and by augmenting the basis set with tight and diffuse functions. The controversy on the sign of a('H,) has been definitely resolved, the sign is found to be positive for all the radicals.

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