ISSN:
1572-9001
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The deviation from tetrahedral configuration at the silicon atom has been studied by modified EHT calculations. The geometry and energy of spiranes M(S2C2H4)2, M=C, Si were optimized with bond lengths constrained at experimental values starting from experimental or assumed geometry. Additionally Si(SR)4, R=H, CH3 as model compounds, have been studied with EHT. Full geometry optimizations with MM2 were also carried out for spiranes M(E2C2R4)2 and M(E2C2H2)2, M=C, Si, Ge, E = O, S, Se and R=H, CH3. The performed MM2 calculations gave no evidence for significant deviation from the ideal spiro configuration. The EHT calculations, on the other hand, show that D2 conformers of Si(S2C2H4)2 and Si(SR)4 are the most stable in somewhat distorted conformation because of the operation of an anomeric effect. The anomeric interactions in S4 conformers do not cause those spiro angle deviations. The energy differences between D2 and S4 conformers are small. The existence of S4 conformers has been predicted in vapor phase by comparison of the observed and calculated splittings of lone pair ionization potentials.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00678411
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