13C-NMR signal

X-ray diffraction studies on [TpBut,Me]Zn 2(/i,-r)1,Tj1-C03) have identified that the bridging carbonate ligand is coordinated to each zinc center in a unidentate fashion (171,172), which thereby provides additional support for the presence of a unidentate, rather than bidentate, bicarbonate ligand in [TpBut,Me]Zn(0C02H). The carbonate complex [TpBut,Me]Zn 2(/iA-7)1,T)1-C03) is also characterized by v(CO) absorptions at 1587 and 1311 cm-1 in the IR spectrum (173), and a 13C NMR signal at 8 164 ppm (in C6D6). 

Chisholm and his group recently succeeded in transforming a metal carbonyl into a stable fi4-carbido complex W4( 4-C)(/t-NMe)(0-i-Pr)12 1 The 13C-NMR signal for the (/ 4-C)4 ligand is 366.8 ppm [5] which can be considered as a realistic model of a surface bound carbido species in the sense of the original proposal by Fischer and Tropsch (Fig. 2). Upon addition of hydrogen, surface bound carbide can be stepwise transformed into methane. 

In relation to the characterization of network structure and dynamics in swollen gels, it seems to be very important to have a prior knowledge of under what conditions the expected 13C NMR signals are visible from... 

Figure 40 13C CPMAS (left) and DDMAS (right) NMR spectra of [3-13C]Ala-ppR alone (a and b) and truncated ppR (1-220) (c and d) reconstituted in egg PC bilayer, respectively. 13C NMR signals from the C-terminal region in ppR are shown in the grey (a and b) and arrows (c and d). The resonance peak at 14.1 ppm is ascribed to the methyl carbon peak of egg PC as shown by the asterisk. From Ref. 215 with permission.

Three pro-inflammatory steryl esters of furan fatty acids (11-13) have recently been isolated from the Mediterranean sponge Dictyonella incisa [30]. The furan moiety was clearly established by H and 13C NMR signals corresponding to... 

The solid state 13C NMR signals of OE in its complexes with a-CD appeared separately from the spectra of a-CD-PEG complexes in a higher magnetic field, in which the signals of the two components were overlapped. This... 

In addition to the determined molecular geometry this is supported by 13C—NMR signals at -158.3 ppm (CVC2) and —155.1 ppm (C3) relative to TMS for comparison, cyclopropenium cation has its 13C-NMR signal at -174 ppm147 ... 

Fig. 2 Schematic representation of the 13C NMR signal of a single crystal containing the functional group AB, oriented (A) perpendicular to the applied field, and (B) parallel to the applied field. The lineshape in (C) represents the NMR signal of a polycrystalline sample with a random distribution of orientations yielding the chemical shift anisotropy pattern displayed. (From Ref. 15.)...

This rule is equally applicable to all types of true nitronates and is the most characteristic parameter of the C=N—>-0 fragment. This is particularly typical of the 13C NMR signals of the a-C atoms, which are shifted to higher field by more than 30 ppm compared to the analogous signals of the corresponding oximes. 

Fig. 8 Temperature dependence -141 °C (bottom trace) to -71 °C (top trace) of 100 MHz 13C NMR signals of the ortho and meta carbons of anti- (86) and syn- (87) l-p-anisyl-2-triisopropylsilyl-ethylcation in S02C1F/S02F2.

Therefore, it is now possible either to record the 13C-NMR signal and place the hydrogens in the undetected second dimension or to record the signal from the hydrogens and place the 13C resonances in the indirect dimension . 

The lower field 13C NMR signals of 76 suggested a substituted pyridone (5116.3 s, 130.0 s, 138.6 s, 151.4 s and 161.3 s) and a 2-diazo-3-oxo-l,4-benzoquinone (687.5 s, 168.8 s, 172.5 s and 173.6 s) moiety by comparison with the reported values of diaza-quinomycin A and 2-diazo-3-oxo-l,4-naphthoquinone, respectively. Similar stabilities of 1- and 2-diazo-3-oxo-1,4-naphthoquinone under acidic conditions indicated the presence of a diazo group in 76. By combining these results, the structure of 76 was assigned. 

FIGURE 50. Cl 13C NMR signal of 6Li-labeled a-lithiomethoxyallene (106) in THF-ds at —100 °C and (b) in diethyl ether at —93 °C. Reprinted with permission from Reference 64. Copyright (1993) American Chemical Society... 

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