29Si-NMR spectrum

Fig. 3a and b. Fast exchange-slow exchange NMR transition for the conformational interconversion of octamethyltetrasiloxane. a, MAS 13C-NMR solid state spectra on the left side in comparison to solution spectra in propane-di on the right side (at 75.47 MHz), b. MAS 29Si-NMR spectra at 59.63 MHz. Temperatures are indicated in K, shift positions refer to TMS = 0 ppm and correspond to the scale at the bottom. (Ref. I0))... 

Disilenes exhibit the relatively low-field (8 = 49-155) 29Si chemical shifts characteristic of low-coordinate silicon compounds (Table I) thus 29Si NMR spectra are very important in their characterization. This deshielding is similar to that observed in the 13C chemical shifts of doubly bonded carbons relative to those of their saturated counterparts. 

The only reported, l9Sn NMR spectrum of a stannanimine (entry 5, Table VI) shows a single signal at the surprisingly high field of 8 = -3.5, for which there is no obvious explanation. The other spectroscopic data, H, 13C, and 29Si NMR spectra, are consistent with the stannanimine structure.88... 

Proton, 13C and 29Si NMR spectra for polysilanes have been recorded.(32) The proton NMR provide little structural information, but integration of areas under the proton resonances is quite useful for determining the composition of copolymers. 

The 29Si NMR spectra are of particular interest because they reflect the configuration of the polymer chain.(33) Some 29Si spectra of alkylpolysilanes are shown in Figure 5. Symmetrically-substituted polymers such as (n-hexyl2Si)a have no chirality since there can be a plane of symmetry through each silicon atom. 

Figure 4. Variable temperature CPMAS 29Si NMR spectra of PDHS (left) and PDPS (right).

Solid state MASS 29Si NMR spectra of dried gels prepared with 4 equivalents of water show a similar trend. QJ-Q4 species are evident in gels prepared under neutral conditions (41), whereas under more basic conditions, Q1 species are absent and Q2 species are greatly reduced relative to Q4 (see NMR results presented below). Thus the effects of restructuring are preserved in the fully dried gel. 

All disilanes and trisilanes were synthesized with methods described in the literature [6]. 29Si NMR spectra were recorded with a BRUKER MSL 300 spectrometer, using solutions of the silanes in C6D6 (app. 50 %). 29Si29Si coupling constants were measured with the standard INADEQUATE pulse sequence. 

Figure 1 shows three 29Si NMR spectra from reaction intervals 20 sec - 40 min, 40 min - 100 min and 100 - 160 min. These results are important for kinetic investigations. Some reported chlorosilanols are listed in Table 2. 

Figure 1. 29Si NMR spectra from the reaction intervals Table 2. Known Chlorosilanols...

Results of 29Si NMR spectroscopy of the Ti-Beta precursor gels are shown in Figure 1. The spectra exhibit peaks that belong to four major types of silica species, Q°, Q1, Q2, and Q3. Here Q" denotes a silicon environment with n Si-O-Si bonds. By comparison of the measured spectra with the 29Si NMR spectra found in the literature [4, 5] we were able to determine that the peak with the chemical shift of -72.9 ppm corresponds to Si monomer Q°, while the peaks at -80.9 ppm and -81.4 ppm are the peaks of Q1 linear trimer and dimer, respectively. The peaks from -83 ppm to -89.8 ppm were contributed to Q2 silicon oligomers, while the peaks at the chemical shifts from -90.3 ppm to -102 ppm were denoted as the part of the Q3 silica species. 

Figure 1. Figure shows the 29Si NMR spectra of Ti-Beta precursor gels that were hydrothermally treated for different periods of time. 

Figure 10b, Magic anglespinning 29Si-NMR spectra of a typical faujasitic zeolite (Si/Al ratio 2.61) before and after dealumination by exposure to SiClk vapor...

Information concerning the structure of 1 in solution stems from 13C, and 29Si NMR spectra.10 They show that only one isomer is present and that this isomer is highly dynamic. A resonance at 8 = —398 ppm in the 29SiNMR... 

Figure 4.12 Comparison of 29Si NMR spectra between (top) poly (S)-3,7-dimethyloctyl-3-methylbutylsilane (16), (middle) poly (S)-3,7-dimethyloctyl-2-methylpropylsilane (17), and (bottom) poly( -decyl-(S)-2-methylbutylsilane) (6) in CDCI3 at 30°C.

Figure 4.20 29Si-NMR spectra of poly[methyl((J>)-2-methylbutoxyphenyl)silane]s (38 and 39) in benzene-Jg at 50°C.

Acetylated poly(phenylsilsesquioxane) characterization, 176-177 molecular structure determination, 176 29Si-NMR spectra, 176,178/ synthesis, 176... 

Figure 32 Solid-state 29Si NMR spectra of (SiMe2),7 at selected temperatures and deconvolution constituents.287 Reprinted with permission from Takayama, T. J. Mol. Struct. 1998, 441, 101-117, 1998 Elsevier.

When 1-phenyl-1-trimethylsilyl ethylchloride 4 is reacted with SbF5 under carefully controlled experimental conditions at -125 °C, the 1-phenyl-1-(trimethylsilyl)ethyl cation 1 is generated exclusively as iridicated by H and 13C (Figure 1) and 29Si NMR spectra (12, 13, 14)... 

Uncalcined samples show three different wSi-NMR peaks which can be assigned to Q2, Q3 and Q4 silicon species. After calcination Q4 environments are formed at the expense of Q3 and Q2. Figure 3 shows two 29Si-NMR spectra of a sample before and after calcination. 

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