Disproportionation of Tetrachlorodimethyldisilane — NMR‐Spectroscopic Identification of the Primary Products

29Si and13C NMR Investigation of the Polysilane-to-Poly(carbosilane) Conversion of Poly(methylchlorosilanes) Using Cross-Polarization and Inversion Recovery Cross-Polarization Techniques

“…Another problem is the assignment of the minor peak D at −51.2 ppm: its chemical shift is in the range of tertiary units, but such downfield values were not found in the liquid NMR study performed on the oligosilanes, for which all the values range from −60 to −67 ppm. , It was thus suggested, in agreement with the TG/MS results that will be presented later, that this peak could be due to the formation of carbosilane units, (−CH 2 )Si(Si) 3 . If this is true, one can wonder why the 13 C resonance peak due to CH 2 groups was not found in the 13 C NMR experiments.…”

“…The spectra were simulated with three peaks at −7.6 ppm (peak a), 4.1 ppm (peak b), and 11.4 ppm (peak c; Table ). According to the NMR study performed on the oligosilanes, , they can be respectively assigned to methyl groups in tertiary or branched units, MeSi(Si) 3 , linear units, MeClSi<, and terminal units, MeCl 2 Si−. A small peak was introduced at 8.5 ppm, to simulate precisely the IRCP spectra, but its intensity is lower than 1% and will not be considered in the following discussion.…”

“…A comparison of the results obtained from 13 C and 29 Si experiments are summarized in Table for the major peaks. The peaks can be assigned by comparison with the liquid NMR study performed on the oligosilanes. , One problem is the assignment of the peak B 2 at 24.2 ppm, which could be due to either linear or terminal groups. Comparison of the quantitative analysis for both nuclei seems to show that this peak is due to linear units with the corresponding 13 C resonance peak b at 4.1 ppm.…”

“…Examination of published data for [(Me) 3 Si] 4 - x Si (Me) x silanes with 0 ≤ x ≤ 4 shows chemical shift values of 0 ppm for x = 4 (Me 4 Si), −19.7 ppm for x = 3 (Me 3 Si (Si)), −48.7 ppm for x = 2 (Me 2 Si (Si) 2 ), −87.9 ppm for x = 1 (Me Si (Si) 3 ) and −135.5 ppm for x = 0 ( Si (Si 4 )) , The 20−30 ppm lowfield shift is certainly related to differences in environments of the first Si neighbors. It is thus expected that in MCPS, quaternary units Si (Si) 4 will be characterized by a chemical shift around −105/−115 ppm.…”

“…For the present study, 1,1,2,2-tetrachlorodimethyldisilane, (MeCl 2 Si−SiCl 2 Me, 2 ) was disproportionated under heterogeneous conditions, which allows one to separate the formed oligomers free from the catalyst using catalytically active dimethylamidophosphoryl groups (D) grafted onto a silicate carrier (eq 1). The methylchlorooligosilanes 3 − 7 that are formed at 175 °C were fully characterized by liquid-phase NMR spectroscopy up to the heptasilane 7 . , For higher reaction temperatures, cross-linking of the oligosilanes occurs. The solid samples investigated in the present study have been obtained for reaction temperatures ranging from 180 to 450 °C.…”