29Si-NMR spectroscopy

Summary The chlorosilanols ClnSi(OH)4.n (n = 3. .. 1) can be seen by 29Si NMR spectroscopy during a partial hydrolysis-condensation of silicon tetrachloride in the NMR tube. 

With 29Si NMR spectroscopy we can show that the chlorosilanol-intermediates of the partial hydrolysis of silicon tetrachloride are stable in solution for more than one houn After fast mixing of diluent water to prevent fast reactions at the dropping point we can see with 29Si NMR Cl3SiOH, Cl2Si(OH)2, and ClSi(OH)3 (table 1). 

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. 

Si NMR spectroscopy reveals that the silicon monomers and dimers start to bind into higher silicon oligomers at the very beginning of the Ti-Beta synthesis procedure. After... 

With the combined methods of 29Si NMR spectroscopy, X-ray diffraction, HRTEM and SAED we were able to characterize the Ti-Beta particle growth. 29Si NMR spectroscopy gave us an opportunity to see the formation of nanoparticles even before they were detectable with other techniques such as XRD. The above mentioned techniques enabled us to obtain sufficient knowledge to prepare Ti-Beta nanoparticles which were than successfully incorporated in novel micro/mesoporous materials [1],... 

Equilibrium processes of intermolecular proton transfer between the thiolate center and SH group are observed in a solution along with the isomerization of betaine 201 to 701. These processes result in salts 71 (Scheme 32) similar to salts 69 in the carbon series, which was proved by 29Si NMR spectroscopy. 

Nakash et al. have studied the reaction of phenylethynyltrifluorosilane 842 with mono- and bidentate nitrogen bases in solution using a combination of H, 13C, 1SN, 19F, and 29Si NMR spectroscopy, which gives rise to formation of... 

Moulin, I., Stone, W. E. E., Sanz, J., Bottero, J.-Y., Mosnier, F. Haehnel, C. 1999. Lead and zinc retention during hydration of tri-calcium silicate, a study by sorption isotherms and 29Si NMR spectroscopy. Langmuir, 15, 2829-2835. 

In the solution state, the possibility of a pentacoordinate silicon species can also be discounted by 29Si NMR spectroscopy (29). Comparison of the silyl nitronates 14 and 6 to the corresponding silyl oximes 15 and 16 show that the silicon resonances are almost identical (Fig. 2.4). If there were a significant interaction with both oxygens in the nitronate, the resonance would be shifted from that of the silyl oxime. 

Miller and Ishida [11] combined size-exclusion chromatography with diffuse reflectance FUR -spectroscopy to identify the hydrolysis and condensation products of phenyltriethoxysilane in mixed organic-aqueous media. Pohl and Osterholtz [8, 12] followed the condensation of alkylsilanols using 3C- and 29Si-NMR spectroscopy and found condensation to be catalyzed by both deuteroxide anion and deuterium ion. Savard etaL [13] used H-NMR spectroscopy to follow the rate of hydrolysis and condensation of 3-methacryloxypropyltrimethoxy-silane as a function of the pH. These authors used the Lentz technique of derivatization to determine the structures of some of the condensation products. 

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