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Part II—1,1,1,2,2,3‐Hexamethyltrisilanes X 2 MeSiSiMe 2 SiMe 3 with X=H, F, Cl, Br, I, C 6 H 5 and OCH 3
Author(s) -
Jähn Anke,
Schenzel Karla,
Zink Robert,
Hassler Karl
Publication year - 1998
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/(sici)1097-4555(199812)29:12<1055::aid-jrs317>3.0.co;2-i
Subject(s) - conformational isomerism , enthalpy , raman spectroscopy , force constant , chemistry , ab initio , standard enthalpy change of formation , crystallography , ab initio quantum chemistry methods , computational chemistry , thermodynamics , standard enthalpy of formation , molecule , physics , quantum mechanics , organic chemistry
The Raman vibrational spectra of the hexamethyltrisilanesX 2 MeSiSiMe 2 SiMe 3 with X=H, F,Cl, Br, I, C 6 H 5 and OCH 3 , recorded atvarious temperatures, prove the simultaneous presence of two rotamers, anti and gauche , in the liquid state. Enthalpydifferences between the rotamers were determined as describedpreviously. Ab initio calculations of equilibrium geometriesand harmonic force constants were performed for anti and gauche X 2 MeSiSiMe 2 SiMe 3 withX=H, F, Cl, Br, I and OCH 3 . Fundamental vibrationswere assigned with the help of normal coordinate analyses andpotential energy distributions were calculated. The preferredconformations of these trisilanes are gauche (CSiSiSitorsional angle near 180°) for X=H, Br, I,OCH 3 and C 6 H 5 , and anti forX=F and Cl with enthalpy differences ranging from 0.25 to 2.2kJ mol ‐1 . © 1998 John Wiley & SonsLtd.