Abstract
The accuracy of calculations of the 29Si NMR chemical shifts of organylsilanes with different hybridization of C atoms in the substituents at the Si atom (sp3, sp2, and sp) was analyzed on the basis of the effective calculation scheme in terms of the density functional theory using the KT3 functional in combination with the ?-polarization consistent basis set pcS-3. Taking into account the influence of the medium in terms of the supermolecular solvate model and relativistic effects based on the full four-component Dirac scheme made it possible to achieve the extremely high accuracy of calculations of 29Si NMR chemical shifts of organylsilanes: 1 ppm for a span of 100 ppm. The contributions of solvent, relativistic, and vibrational corrections for the 29Si NMR chemical shifts are 3, 1, and 1 ppm, respectively, and taking them into account noticeably improves the agreement of calculation results with experiment. The relativistic shielding contribution to the absolute shielding constant of the Si atom is 12—13 ppm on the average, i.e., to ca. 3% in the relative expression.
Published Version
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