Schwingungsspektren von Methylpentafluorosilicaten und Normalkoordinatenanalyse des Methylpentafluorosilications

Abstract

Mit 1 Abbildung Inhaltsiibersicht. Von (NH.J2-, Kz-, Rb,-und Cs,[CH,SiF,] wurden die RAMANund IR-Spektren (400-4000 cm-l, z. T. auch 200-400 cm-l) gemessen und die in den Spektren auftretenden Linien bzw. Banden weitgehend zugeordnet. Ferner wurde eine Normalkoordinatenanalyse des [CH,SiF,]"-Ions durchgefuhrt. Mit Hilfe der IR-Spektroskopie wurde ferner die Bestandigkeit der Methylpentafluorosilicate untersucht.A b s t r a c t . The RAMAB and I R spectra (400-4000 cm-l, partly also 200-400 cm-l) of (NH4)2-, Kz-, Rbz-and Cs,[CH,SiF,] were recorded and the bands were assigned. A normal coordinate calculation of the [CH,SiF,I2-ion has been made. By means of I R spectroscopy the stability of the methylpentafluorosilicates were examined.

Silicon−Fluorine and Silicon−Carbon Bond Cleavage in Organofluorosilicates: A Molecular Orbital Study

“…The calculations show greater bond lengthening of 11−14% in PhSiF 5 2- (3-21G* and 6-31G*), relative to PhSiF 3 . These calculations are in agreement with IR studies which indicate that the force constant of the Si−C bond, as well as of the Si−F bond, in MeSiF 5 2- , is smaller than that in MeSiF 3 . Since NMR studies have shown that Si−C bond cleavage does not occur in these purified compounds under mild conditions, we may therefore conclude that a bond lengthening of about 4−12% is insufficient to cause Si−C bond cleavage in PhSiF 4 - or PhSiF 5 2- under mild thermal conditions.…”