Strong Intramolecular Si-N Interactions in the Chlorosilanes Cl3-nHnSiOCH2CH2NMe2 (n=1-3)

Hagemann M, Mix A, Berger R, Pape T, Mitzel NW (2008)
INORGANIC CHEMISTRY 47(22): 10554-10564.

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Abstract
The compounds Cl3SiOCH2CH2NMe2 (1) and Cl2HSiOCH2CH2NMe2 (2) were prepared by reactions of lithium 2-(dimethylamino)ethanolate with SiCl4 and HSO3. The analogous reaction with H2SiCl2 gave ClH2SiOCH2CH2NMe2 (3), but only in a mixture with Cl2HSiOCH2CH2NMe2 (2), from which it could not be separated. All compounds were characterized by IR and NMR (1(H), C-13, Si-29) spectroscopy, 1 and 2 by elemental analyses and by determination of their crystal structures. Cl3SiOCH2CH2NMe2 (1) and Cl2HSiOCH2CH2NMe2 (2) crystallize as monomeric ring compounds with pentacoordinate silicon atoms participating in intramolecular Si-N bonds [2.060(2) angstrom (1), 2.037(2) A (2)]. The dative bonds in 1 and 2 between the silicon and nitrogen atoms could also be proven to exist at low temperatures in solution in H-1, Si-29-HMBC-NMR experiments by detection of the scalar coupling between the 29Si and the protons of the NCH2 and NCH3 groups. A function describing the chemical shift delta Si-29(exp) dependent on the chemical shifts of the individual equilibrium components, the temperature, and the free enthalpy of reaction was worked out and fitted to the experimental VT-NMR data of 1 and 2. This provided values of the free reaction enthalpies of Delta G = -28.8 +/- 3.9 kJ . mol(-1) for 1 and Delta G = -22.3 +/- 0.4 kJ . mol(-1) for 2 and estimates for the chemical shifts of open-chain (index o) and ring conformers (index r) for 1 of delta(r) = -94 +/- 2 ppm and delta(o) = -36 +/- 5 ppm and for 2 of delta(r) = -82 +/- 1 ppm and delta(o) = -33 +/- 4 ppm. The value of delta(r) for 1 is very close to that obtained from a solid-state Si-29 MAS NMR spectrum. Quantumchemical calculations (up to MP2/TZVPP) gave largely differing geometries for 1 (with a Si...N distance of 3.072 angstrom), but well reproduced the geometry of 2. These differences are due to Cl...H and Cl...C repulsions and solid state effects, which can be modeled by conductor-like screening model calculations and also rationalized in terms of the topology of the electron density, which was analyzed in terms of the quantum theory of atoms in molecules.
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Hagemann M, Mix A, Berger R, Pape T, Mitzel NW. Strong Intramolecular Si-N Interactions in the Chlorosilanes Cl3-nHnSiOCH2CH2NMe2 (n=1-3). INORGANIC CHEMISTRY. 2008;47(22):10554-10564.
Hagemann, M., Mix, A., Berger, R., Pape, T., & Mitzel, N. W. (2008). Strong Intramolecular Si-N Interactions in the Chlorosilanes Cl3-nHnSiOCH2CH2NMe2 (n=1-3). INORGANIC CHEMISTRY, 47(22), 10554-10564.
Hagemann, M., Mix, A., Berger, R., Pape, T., and Mitzel, N. W. (2008). Strong Intramolecular Si-N Interactions in the Chlorosilanes Cl3-nHnSiOCH2CH2NMe2 (n=1-3). INORGANIC CHEMISTRY 47, 10554-10564.
Hagemann, M., et al., 2008. Strong Intramolecular Si-N Interactions in the Chlorosilanes Cl3-nHnSiOCH2CH2NMe2 (n=1-3). INORGANIC CHEMISTRY, 47(22), p 10554-10564.
M. Hagemann, et al., “Strong Intramolecular Si-N Interactions in the Chlorosilanes Cl3-nHnSiOCH2CH2NMe2 (n=1-3)”, INORGANIC CHEMISTRY, vol. 47, 2008, pp. 10554-10564.
Hagemann, M., Mix, A., Berger, R., Pape, T., Mitzel, N.W.: Strong Intramolecular Si-N Interactions in the Chlorosilanes Cl3-nHnSiOCH2CH2NMe2 (n=1-3). INORGANIC CHEMISTRY. 47, 10554-10564 (2008).
Hagemann, Michael, Mix, Andreas, Berger, Raphael, Pape, Tania, and Mitzel, Norbert W. “Strong Intramolecular Si-N Interactions in the Chlorosilanes Cl3-nHnSiOCH2CH2NMe2 (n=1-3)”. INORGANIC CHEMISTRY 47.22 (2008): 10554-10564.
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