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The (Chloromethyl)dihalosilanes X 2 HSiCH 2 Cl (X = F, Cl, Br, I): Synthesis, Multinuclear NMR Spectroscopy and Rotational Isomerism Examined by Raman Spectroscopy
Author(s) -
Hassler Karl,
Hummeltenberg Reinhard,
Tekautz Günter
Publication year - 2004
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200400305
Subject(s) - chemistry , conformational isomerism , raman spectroscopy , enthalpy , ab initio quantum chemistry methods , ab initio , spectroscopy , nuclear magnetic resonance spectroscopy , crystallography , nmr spectra database , infrared spectroscopy , iodide , analytical chemistry (journal) , computational chemistry , spectral line , stereochemistry , molecule , inorganic chemistry , organic chemistry , physics , quantum mechanics , astronomy , optics
(Chloromethyl)diphenylsilane Ph 2 HSiCH 2 Cl ( 1 ) was prepared from Ph 2 SiHCl and LiCH 2 Cl, in situ, and was then treated with CF 3 SO 3 H/LiCl and CF 3 SO 3 H/LiBr to give the (chloromethyl)dihalosilanes Cl 2 HSiCH 2 Cl ( 2 ) and Br 2 HSiCH 2 Cl ( 3 ). I 2 HSiCH 2 Cl ( 4 ) was formed quantitatively in a protodearylation reaction between liquid hydrogen iodide and 1 . Fluorination of 4 with ZnF 2 gave F 2 HSiCH 2 Cl ( 5 ), albeit in low yields. Compounds 1 − 5 were characterised by multinuclear NMR spectroscopy ( 29 Si, 13 C, 19 F) and vibrational spectroscopy. The temperature‐dependent vibrational Raman spectra of 2 , 3 and 4 prove that they are mixtures of gauche and anti rotamers in the liquid state. Enthalpy differences, Δ H ( H anti − H gauche ), were determined for the liquids by applying the van’t Hoff relation, with the gauche rotamer being lower in energy for 3 and 4 , and the anti rotamer for 2 . The vibrational spectra were assigned with the help of ab initio calculations of equilibrium geometries and harmonic fundamental frequencies. Harmonic symmetry force constants and potential energy distributions were calculated from the ab initio Hessian matrices. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)