Satellite signals

Fig. 42a-c Spectra of tetramethyltin in CDC13. a Proton decoupled, b proton coupled (2JsncH 54.3 Hz), c proton spectrum. The satellite signals are due to coupling to tin-117 (inner lines) and tin-119 (outer lines). The ratio of the coupling with tin-119 to that with tin-117 is 1.046 1 (the ratio of the magnetogyric ratios of the two nuclei)... 

Fig. 5b. Comparison of the results obtained with the basic (left) and the multiple selective (right) INADEQUATE experiment. The signals of C-10, C-16, C-17 and C-18 are shown and are compared with the responses measured with the modified experiment after perturbation of C-15. Corresponding satellite signals are connected by horizontal lines.

The two-dimensional INADEQUATE experiment also suffers very much from low sensitivity given by the low natural abundance of carbon-13 (about 10 2), so that only 0.01 % or 10-4 of all carbon-carbon bonds contribute to the satellite signals. In fact, the basic experiment can be modified in order to reduce the data matrix and to save measuring time [72], giving COSY-like square correlations as shown in Fig. 2.60. Nevertheless, the two-dimensional INADEQUATE experiment requires several hours of measuring... 

Fig. 9.12. XPE spectra of the 3d region of Ce02 showing various satellite signals along with 3d5/2 and 3d3/2...

Satellites are not restricted to 13C, but may be seen with other magnetic nuclei that are present at low abundance when the principal isotope has 1=0. Among the best known are 29Si (8.5%), nlCd and l13Cd (each about 9%), 199Hg (7.6%), and 207Pb (8.9%). Other nuclides, such as 15N, have a natural abundance so low that satellite signals are rarely observed in normal one-dimensional NMR spectra, but with polarization transfer methods described in Chapters 9 and 10, the existence of these weak satellites often permits observation of the less sensitive, low abundance nuclide by indirect detection. 

At RT, solutions of (Me3Si)2Hg or (Me3Ge)2Hg show a single H-NMR resonance flanked by Hg satellites. As the temperature is raised the satellite signals broaden and finally collapse as the exchange rate becomes rapid on the NMR time scale. Exchange reactions between different silylmercurials and between silylmercurials and mercury dialkyls are elucidated by NMR, e.g. ... 

Compound (14) can easily be identified by Si/ H HETCOR experiments indicating the couplings of Si nuclei over two or three bonds to the BCH and BCHj protons, respectively ((5 Si = 3.0), and over three bonds to the C-2 Mes protons (c) Si = —7.0). The Si NMR spectrum also allows the observation of C satellite signals. The relatively small coupling constant /( Si- C(2)) = 18.2 Hz is typical for the accumulation of electropositive substituents at carbon <79ZN(B)1270,91SA(A)849>. 

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