were synthesized from the corresponding disiloxanes 1a−f using Et 2 O•BF 3 . According to the NMR and IR data, the extent of dimerization of fluorosilanes 2a−f 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 19 F 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 SiMe 2 signals in the 1 H 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 N-(dimethylsilylmethyl) and N-(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.
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