Tamao, Kohei published the artcileElectronic and steric effects in pentacoordinate anionic diorganotrifluorosilicates: x-ray structures and carbon-13 NMR studies for evaluation of charge distribution in aryl groups on silicon, Quality Control of 312-40-3, the publication is Organometallics (1992), 11(1), 182-91, database is CAplus.
A series of diorganotrifluorosilicates, (4-XC6H4)MeSiF3– (I), (4-XC6H4)PhSiF3– (II), (MenC6H5-n)PhSiF3–, (2-MeC6H4)(4-MeC6H4)SiF3– (III), and (2,6-Me2C6H3)(3,5-Me2C6H3)SiF3– (IV) with the 18-crown-6 potassium countercation were prepared Mol. structures of II (X = CF3, Me, MeO, Me2N), III, and IV were determined by X-ray crystallog., confirming trigonal-bipyramidal structures. The dihedral angle between the substituted Ph group and the equatorial plane depends not on the electronic effect but on the steric effect. Variable-temperature 19F NMR studies on II provide the electronic effects on energy barriers for pseudorotation. In 13C NMR studies, all carbon chem. shifts were observed and assigned unambiguously: the Si ipso carbons of aromatic rings and the Me group were observed for the first time. Changes in chem. shifts ¦¤¦Ä(C) of anionic pentacoordinate silicates, I and II, vs. the corresponding neutral tetracoordinate silanes are +17 to +20 ppm for Si ipso (C1), +3 to +4 ppm for ortho (C2), -3 ppm for meta (C3), -4 to -7 ppm for para (C4), and +9 ppm for Me carbon. The charge distribution in the Ph groups in silicates is discussed in terms of the electron-donating nature by the SiRF3– group via the ¦Ð polarization effect. There are linear correlations of the chem. shifts of Si ipso C1 (para to X) in the para-substituted Ph groups and Si ipso C1′ in the parent Ph groups in II and (4-XC6H4)PhSiF2 with the Hammett ¦Òp+, from which are estimated the relative electron densities on Si ipso carbons C1 and C1′.
Organometallics published new progress about 312-40-3. 312-40-3 belongs to catalysis-chemistry, auxiliary class Organic Silicones, name is Difluorodiphenylsilane, and the molecular formula is C9H7NO2, Quality Control of 312-40-3.
Referemce:
https://courses.lumenlearning.com/boundless-chemistry/chapter/catalysis/,
Catalysis – Wikipedia