Synthesis, Structures, and Stereodynamic Behavior of Novel Pentacoordinate Fluorosilanes: Fluorosilyl Derivatives of Proline

The (O→Si)-chelate <i>N</i>′-(dimethylfluorosilylmethyl))-<i>N</i>′-methyl-<i>N</i>-(organosulfonyl)­prolinamides RSO₂-Pro-N­(Me)­CH₂SiMe₂F (<b>2a</b>–<b>f</b>, R = Me (<b>a</b>), Ph (<b>b</b>), 4-MeC₆H₄ (<b>c</b>), 4-ClC₆H₄ (<b>d</b>), 4-BrC₆H₄ (<b>e</b>), 4-NO₂C₆H₄ (<b>f</b>)) were synthesized from the corresponding disiloxanes <b>1a</b>–<b>f</b> using Et₂O·BF₃. According to the NMR and IR data, the extent of dimerization of fluorosilanes <b>2a</b>–<b>f</b> in solution is negligible, while the O→Si coordination in solution is weaker than that in the solid state. Comparative CP/MAS NMR and X-ray diffraction studies revealed that in solution the coordination Si–O bond length varies in a narrow range (2.22–2.24 Å) that is 0.02–0.11 Å longer than in the crystalline state. Dynamic NMR (DNMR) studies of the fluorides revealed a fine structure of the ¹⁹F signals in the 0–20 °C temperature range, which was related to the structural features of the coordination set in these complexes. The temperature dependence of the SiMe₂ signals in the ¹H DNMR spectra was attributed to a permutational isomerization process involving a positional exchange of equatorial ligands. The narrow range of activational barriers of the process (23–24 kcal mol^–1 and more) and high negative values of the entropy of activation are similar to those observed earlier for Si-substituted <i>N</i>-(dimethylsilylmethyl) and <i>N</i>-(methylphenylsilylmethyl) amides and lactams, which suggests similar permutational processes in all cases. Gas-phase quantum chemical studies demonstrate that the solvation of F^– reduces the activation barrier

Synthesis, Structures, and Stereodynamic Behavior of Novel Pentacoordinate Fluorosilanes: Fluorosilyl Derivatives of Proline

The (O→Si)-chelate <i>N</i>′-(dimethylfluorosilylmethyl))-<i>N</i>′-methyl-<i>N</i>-(organosulfonyl)­prolinamides RSO₂-Pro-N­(Me)­CH₂SiMe₂F (<b>2a</b>–<b>f</b>, R = Me (<b>a</b>), Ph (<b>b</b>), 4-MeC₆H₄ (<b>c</b>), 4-ClC₆H₄ (<b>d</b>), 4-BrC₆H₄ (<b>e</b>), 4-NO₂C₆H₄ (<b>f</b>)) were synthesized from the corresponding disiloxanes <b>1a</b>–<b>f</b> using Et₂O·BF₃. According to the NMR and IR data, the extent of dimerization of fluorosilanes <b>2a</b>–<b>f</b> in solution is negligible, while the O→Si coordination in solution is weaker than that in the solid state. Comparative CP/MAS NMR and X-ray diffraction studies revealed that in solution the coordination Si–O bond length varies in a narrow range (2.22–2.24 Å) that is 0.02–0.11 Å longer than in the crystalline state. Dynamic NMR (DNMR) studies of the fluorides revealed a fine structure of the ¹⁹F signals in the 0–20 °C temperature range, which was related to the structural features of the coordination set in these complexes. The temperature dependence of the SiMe₂ signals in the ¹H DNMR spectra was attributed to a permutational isomerization process involving a positional exchange of equatorial ligands. The narrow range of activational barriers of the process (23–24 kcal mol^–1 and more) and high negative values of the entropy of activation are similar to those observed earlier for Si-substituted <i>N</i>-(dimethylsilylmethyl) and <i>N</i>-(methylphenylsilylmethyl) amides and lactams, which suggests similar permutational processes in all cases. Gas-phase quantum chemical studies demonstrate that the solvation of F^– reduces the activation barrier

Synthesis, Structures, and Stereodynamic Behavior of Novel Pentacoordinate Fluorosilanes: Fluorosilyl Derivatives of Proline

The (O→Si)-chelate <i>N</i>′-(dimethylfluorosilylmethyl))-<i>N</i>′-methyl-<i>N</i>-(organosulfonyl)­prolinamides RSO₂-Pro-N­(Me)­CH₂SiMe₂F (<b>2a</b>–<b>f</b>, R = Me (<b>a</b>), Ph (<b>b</b>), 4-MeC₆H₄ (<b>c</b>), 4-ClC₆H₄ (<b>d</b>), 4-BrC₆H₄ (<b>e</b>), 4-NO₂C₆H₄ (<b>f</b>)) were synthesized from the corresponding disiloxanes <b>1a</b>–<b>f</b> using Et₂O·BF₃. According to the NMR and IR data, the extent of dimerization of fluorosilanes <b>2a</b>–<b>f</b> in solution is negligible, while the O→Si coordination in solution is weaker than that in the solid state. Comparative CP/MAS NMR and X-ray diffraction studies revealed that in solution the coordination Si–O bond length varies in a narrow range (2.22–2.24 Å) that is 0.02–0.11 Å longer than in the crystalline state. Dynamic NMR (DNMR) studies of the fluorides revealed a fine structure of the ¹⁹F signals in the 0–20 °C temperature range, which was related to the structural features of the coordination set in these complexes. The temperature dependence of the SiMe₂ signals in the ¹H DNMR spectra was attributed to a permutational isomerization process involving a positional exchange of equatorial ligands. The narrow range of activational barriers of the process (23–24 kcal mol^–1 and more) and high negative values of the entropy of activation are similar to those observed earlier for Si-substituted <i>N</i>-(dimethylsilylmethyl) and <i>N</i>-(methylphenylsilylmethyl) amides and lactams, which suggests similar permutational processes in all cases. Gas-phase quantum chemical studies demonstrate that the solvation of F^– reduces the activation barrier

Synthesis, Structures, and Stereodynamic Behavior of Novel Pentacoordinate Fluorosilanes: Fluorosilyl Derivatives of Proline

The (O→Si)-chelate <i>N</i>′-(dimethylfluorosilylmethyl))-<i>N</i>′-methyl-<i>N</i>-(organosulfonyl)­prolinamides RSO₂-Pro-N­(Me)­CH₂SiMe₂F (<b>2a</b>–<b>f</b>, R = Me (<b>a</b>), Ph (<b>b</b>), 4-MeC₆H₄ (<b>c</b>), 4-ClC₆H₄ (<b>d</b>), 4-BrC₆H₄ (<b>e</b>), 4-NO₂C₆H₄ (<b>f</b>)) were synthesized from the corresponding disiloxanes <b>1a</b>–<b>f</b> using Et₂O·BF₃. According to the NMR and IR data, the extent of dimerization of fluorosilanes <b>2a</b>–<b>f</b> in solution is negligible, while the O→Si coordination in solution is weaker than that in the solid state. Comparative CP/MAS NMR and X-ray diffraction studies revealed that in solution the coordination Si–O bond length varies in a narrow range (2.22–2.24 Å) that is 0.02–0.11 Å longer than in the crystalline state. Dynamic NMR (DNMR) studies of the fluorides revealed a fine structure of the ¹⁹F signals in the 0–20 °C temperature range, which was related to the structural features of the coordination set in these complexes. The temperature dependence of the SiMe₂ signals in the ¹H DNMR spectra was attributed to a permutational isomerization process involving a positional exchange of equatorial ligands. The narrow range of activational barriers of the process (23–24 kcal mol^–1 and more) and high negative values of the entropy of activation are similar to those observed earlier for Si-substituted <i>N</i>-(dimethylsilylmethyl) and <i>N</i>-(methylphenylsilylmethyl) amides and lactams, which suggests similar permutational processes in all cases. Gas-phase quantum chemical studies demonstrate that the solvation of F^– reduces the activation barrier

Synthesis, Structures, and Stereodynamic Behavior of Novel Pentacoordinate Fluorosilanes: Fluorosilyl Derivatives of Proline

The (O→Si)-chelate <i>N</i>′-(dimethylfluorosilylmethyl))-<i>N</i>′-methyl-<i>N</i>-(organosulfonyl)­prolinamides RSO₂-Pro-N­(Me)­CH₂SiMe₂F (<b>2a</b>–<b>f</b>, R = Me (<b>a</b>), Ph (<b>b</b>), 4-MeC₆H₄ (<b>c</b>), 4-ClC₆H₄ (<b>d</b>), 4-BrC₆H₄ (<b>e</b>), 4-NO₂C₆H₄ (<b>f</b>)) were synthesized from the corresponding disiloxanes <b>1a</b>–<b>f</b> using Et₂O·BF₃. According to the NMR and IR data, the extent of dimerization of fluorosilanes <b>2a</b>–<b>f</b> in solution is negligible, while the O→Si coordination in solution is weaker than that in the solid state. Comparative CP/MAS NMR and X-ray diffraction studies revealed that in solution the coordination Si–O bond length varies in a narrow range (2.22–2.24 Å) that is 0.02–0.11 Å longer than in the crystalline state. Dynamic NMR (DNMR) studies of the fluorides revealed a fine structure of the ¹⁹F signals in the 0–20 °C temperature range, which was related to the structural features of the coordination set in these complexes. The temperature dependence of the SiMe₂ signals in the ¹H DNMR spectra was attributed to a permutational isomerization process involving a positional exchange of equatorial ligands. The narrow range of activational barriers of the process (23–24 kcal mol^–1 and more) and high negative values of the entropy of activation are similar to those observed earlier for Si-substituted <i>N</i>-(dimethylsilylmethyl) and <i>N</i>-(methylphenylsilylmethyl) amides and lactams, which suggests similar permutational processes in all cases. Gas-phase quantum chemical studies demonstrate that the solvation of F^– reduces the activation barrier

Synthesis, Structures, and Stereodynamic Behavior of Novel Pentacoordinate Fluorosilanes: Fluorosilyl Derivatives of Proline

The (O→Si)-chelate <i>N</i>′-(dimethylfluorosilylmethyl))-<i>N</i>′-methyl-<i>N</i>-(organosulfonyl)­prolinamides RSO₂-Pro-N­(Me)­CH₂SiMe₂F (<b>2a</b>–<b>f</b>, R = Me (<b>a</b>), Ph (<b>b</b>), 4-MeC₆H₄ (<b>c</b>), 4-ClC₆H₄ (<b>d</b>), 4-BrC₆H₄ (<b>e</b>), 4-NO₂C₆H₄ (<b>f</b>)) were synthesized from the corresponding disiloxanes <b>1a</b>–<b>f</b> using Et₂O·BF₃. According to the NMR and IR data, the extent of dimerization of fluorosilanes <b>2a</b>–<b>f</b> in solution is negligible, while the O→Si coordination in solution is weaker than that in the solid state. Comparative CP/MAS NMR and X-ray diffraction studies revealed that in solution the coordination Si–O bond length varies in a narrow range (2.22–2.24 Å) that is 0.02–0.11 Å longer than in the crystalline state. Dynamic NMR (DNMR) studies of the fluorides revealed a fine structure of the ¹⁹F signals in the 0–20 °C temperature range, which was related to the structural features of the coordination set in these complexes. The temperature dependence of the SiMe₂ signals in the ¹H DNMR spectra was attributed to a permutational isomerization process involving a positional exchange of equatorial ligands. The narrow range of activational barriers of the process (23–24 kcal mol^–1 and more) and high negative values of the entropy of activation are similar to those observed earlier for Si-substituted <i>N</i>-(dimethylsilylmethyl) and <i>N</i>-(methylphenylsilylmethyl) amides and lactams, which suggests similar permutational processes in all cases. Gas-phase quantum chemical studies demonstrate that the solvation of F^– reduces the activation barrier