29Si reference compound

The proton decoupled 29Si spectrum of tetram-ethylsilane (TMS) is shown at the top of Figure 6.9 with the proton coupled spectrum for comparison as an inset. TMS is the obvious choice for a 29Si reference compound and we set it at zero ppm. The proton-coupled spectrum is quite interesting because the 29Si nucleus is coupled to 12 equivalent protons in TMS. First order rules predict a multiplet with 13 peaks. There are 9 peaks clearly visible and 11 with a little imagination we do not see the full 13 peaks because the outer ones are too weak and are lost in the noise. 

FIGURE 18. The correlation between one-bond A M(13/12C) isotope shifts in the 29Si and 119Sn NMR spectra of isostructural acetylenes (CH3)3 M.Ca=Cp X (M = 29Si, 119Sn). The numbering of the compounds corresponds to that in Table 11. Reproduced by permission of Elsevier Science from Reference 107... 

FIGURE 31. Summary chart of the principal components for the 29Si shielding tensors of the compounds studied. Axial symmetry is indicated by the double intensity of lines at The arrows indicate the isotropic values. The shielding scale is relative to the isotropic value for tetramethylsilane. Reproduced by permission of the Royal Society of Chemistry from Reference 140... 

FIGURE 15. Normal INEPT (bottom) and SPINEPTR (top) 29Si NMR spectra and the resulting assignment for the compound shown in the inset. Reprinted from Reference 21, Copyright 1990, with permission from Elsevier Science... 

FIGURE 23. H—29Si HMBS spectrum of compound 14 in 1 1 CDCI3— CS2 mixture. [Value of 3/(29Si— H) used for setting up correlation experiment not given.] Reprinted with permission from Reference 208. Copyright 1995 American Chemical Society... 

Compound Double bond length (A) 29Si NMR (ppm) IR (cm ) Reference(s)... 

The signals in the 29si-NMR spectra were assigned with reference to the literature data and the spectra of a number of model compounds (21) (m -88 ppm -monosiloxy-substituted units m - -95 ppm -disiloxy-substituted units m at -100-105 ppm tri- and tetrasiloxy-substituted units). The 29si NMR spectral data (Fig. 2) make it possible to determine the proportions of various structural units as constituent parts of the molecule of the end product ... 

---