Protons without coupling constants, multiplicity

In heteronuclear y-resolved spectra chemical shifts of an arbitrary nucleus X which couples with protons (this is mostly are presented on one axis and proton-X J couplings on the other. The information content is equivalent to that in a proton-coupled "C spectrum (Fig. 12) but without the severe overlap of multiplets which is usually encountered in the latter. In common with off-resonance proton decoupling, y-modulated spin echo, and DEPT experiments, it facilitates multiplicity determination. In addition, it enables proton-X coupling constants to be measured. 

DEPT spectra can be detected with and without proton decoupling. Correspondingly, decoupled and coupled spectra with multiplicity selection are observable. Fig. 2.46 illustrates such experiments with ( — (-menthol, also providing clear analysis of all CH coupling constants of the molecule. 

In addition to investigations this important class of compound may also be studied by means of MAS NMR spectroscopy. In fact we have shown that sharp resonances may be obtained from solid state MAS NMR of molecular hydrido carbonyl complexes without recourse either to the multiple pulse methods [22] or to isotopic dilution [23]. This is due to the fact that in these compounds the protons are intramolecularly diluted. We considered again H20s3(CO)io which crystallizes with one molecule as the asymmetric unit, as determined by a neutron diffraction study [24], and displays an interproton distance of 2.38 A. This interproton distance affords a dipolar coupling constant of 8.91 kHz. Now, rotation of the sample at 8.1 kHz allows... 

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