Radical anions of hypervalent silicon compounds: 1-substituted silatranes†
The first representatives of the radical anions of silatranes XSi(OCH2CH2)3N – organic derivatives of the pentacoordinate silicon atom (X = Ph, 1; p-NO2PhO, 2a; m-NO2PhO, 2b; o-NO2PhO, 2c) – were obtained and characterized by EPR spectroscopy. The structure of 1−˙, 2a−˙, 2b−˙, and 2c−˙ in polar solvents (C-PCM and COSMO models) was studied at the UMP2 and UB3PW91 levels of theory. The variation of structural characteristics and pentacoordinate character of the silicon atom in 1, 2 upon the attachment of an additional electron to them is discussed. The experimental hyperfine coupling constants aN, aH and those calculated with the UTPSSh/IGLOIII and UB3LYP/N07D methods using the UB3PW91 geometry (taking into account an effect of the potassium cation in the case of 1−˙) are in good mutual agreement.