29SiNMR

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... 

Recently, high resolution solution and solid state 29Si NMR studies have been conducted on the polysilanes (RR Si)w124 127. It is obvious that this technique will be a powerful method for determining the microstructure of these polymers. Figure 12 shows a comparison between the 29SiNMR spectrum of poly(methyl-n-hexylsilane) and poly(di-n-hexylsilane)124. In the former case the effects of tacticity can be seen in the fine structure of the spectrum whereas in the latter case for which this is impossible only a single peak is observed. 

More recently 29SiNMR has been used to determine the structure of the various components of silicon resins containing M, DOH and T units130. In addition to the expected effects of sequencing on the chemical shifts, diastereotopic M groups were observed in several cases including molecule ... 

An NMR study21 showed that the 29SiNMR resonance in silanols was dependent on the basicity of the solvent. A linear correlation between <529Si and the Gutmann donor number3,4 22 was observed. 

For arylpolysilanes the results are quite different. The 29SiNMR for (PhSiMe) is shown in Figure 13 it consists of three broad lines with relative intensity 3 3 4, each line... 

TABLE 4. Molar percentage of various siloxane units of a methyl/vinyl branched fluid as determined by 29SiNMR°... 

H, 13C and 29SiNMR spectroscopy have been used extensively to assign structures and study fluxional processes in transition-metal silyl complexes. For example, cobalt silyls (CO)4CoSiR3 (R = Ph, F, Cl) are fluxional in solution as determined by variable-... 

The molecular structure of polycarhosilane is difficult to represent precisely. However, from measurements of the molecular weight, the intrinsic viscosity, infared and ultraviolet spectroscopy, proton, carbon, and silicon nuclear magnetic resonance (IH, and 29SiNMR), and chemical analysis, the structure of polycarhosilane is found to be represented by three simple units. These are silicon bonded with four carbon atoms (SiC4), silicon bonded with three carbon atoms (SiCsH), and silicon bonded with x carbon atoms and 4 - x silicon atoms (SiCjcSi4-x, x = 1, 2, or 3). These are shown by the following stmctural units [18] ... 

TABLE 7 Faujasitic Zeolites. Differences in A1 Distribution Revealed by 29siNMR... 

Species Che imcS lSfts (ppm) Species 29siNMR Chemical shifts (ppm)... 

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