Part II—1,1,1,2,2,3-Hexamethyltrisilanes X2MeSiSiMe2SiMe3 with X=H, F, Cl, Br, I, C6H5 and OCH3

✍ Scribed by Anke Jähn; Karla Schenzel; Robert Zink; Karl Hassler

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 154 KB
• Volume: 29
• Category: Article
• ISSN: 0377-0486
• DOI: 10.1002/(sici)1097-4555(199812)29:12<1055::aid-jrs317>3.0.co;2-i

✦ Synopsis

The Raman vibrational spectra of the hexamethyltrisilanes with X = H, F, Cl, Br, I, X 2 MeSiSiMe 2 SiMe 3 C 6 H 5 and recorded at various temperatures, prove the simultaneous presence of two rotamers, anti and gauche, OCH 3 , in the liquid state. Enthalpy di †erences between the rotamers were determined as described previously. Ab initio calculations of equilibrium geometries and harmonic force constants were performed for anti and gauche with X = H, F, Cl, Br, I and Fundamental vibrations were assigned with the help of X 2 MeSiSiMe 2 SiMe 3 OCH 3 . normal coordinate analyses and potential energy distributions were calculated. The preferred conformations of these trisilanes are gauche (CSiSiSi torsional angle near 180Ä) for X = H, Br, I, and and anti for OCH 3 C 6 H 5 , X = F and Cl with enthalpy di †erences ranging from 0.25 to 2.2 kJ mol-1.