Metals NMR spectra

Also rather few solid state metal NMR spectra of clusters have been reported. This type of experiment is very promising for the metal NMR of clusters, basically for two reasons. First, solid state NMR gives tensorial values of the chemical shifts, and the anistropy of coupling constants reflecting more precisely the electronic structure. The measurement of dipole-dipole interactions, where possible, should allow the determination of distances involving light nuclei such as H, Li, Be which are not easily accessible by X-ray diffraction. The second reason for interest in solid state studies is that the fluxional behaviour is often frozen out and that consequently NMR results are more amenable to correlation with X-ray studies. 

Alkali metal NMR spectra were observed at the appropriate resonance frequencies listed in Table I, using 12-mm tubes and a Varian XL-100 spectrometer with Gyrocode Observe capability. External 19F or internal H field-frequency lock was used. Depending on the linewidth of the resonance being observed, spectral widths of 256 Hz to 12 kHz in 8192 frequency domain points were used. For 23Na and 85Rb, 90° pulses of 50/isec and a 0.1-sec repetition rate were used. For 6Li and 133Cs, the approximately 55° pulses were 30 /xsec, and the pulse repetition rates for the Nafion samples were 60 sec and 1 sec, respectively. 

Other relevant material is contained in reviews on homogeneous catalysis of organic reactions by transition metal complexes, highly reduced metal carbonyl complexes, phosphine complexes of the early transition metal complexes and the lanthanoids, metal NMR spectra of transition metal organometallic systems, the coordination chemistry of C-Nitroso-compounds, mono-Cp halide complexes of the d- and/-block, and organometallic chemistry in the gas phase. o... 

Often dynamically broadened alkali metal NMR spectra can be seen as a result of exchange between the free and complexed cation. A good example is provided by the dynamic Li and Na spectra for the interaction of Li" and Na with the pendant arm macrocycle 1,4,7510-tetrakis(2-methoxyethyl)-l, 4,7,10-tetraazacyclododecane [3]. The dynamic Li spectra are shown in Figure 5. Evidence of a slowly exchanging 1 1 complex and of a 2 1 complex in rapid equilibrium with the 1 1 complex between calixarene [4]... 

The preparation of a series of transition metal complexes (Co. Ni. Pd. Pt, Ir. Au. Cu. Ag) with ambident anion (70) and phosphines as ligands has been reported recently (885). According to the infrared and NMR spectra the thiazoline-2-thione anion is bounded through the exocyclic sulfur atom to the metal. The copper and silver complexes have been found to be dimeric. 

All the known porphyrin isomers are typical benzoid aromatic compounds which show distinctly porphyrin-like characteristic electronic absorption spectra.13 Also the complexation properties for metal ions, NH tautomerism and the NMR spectra are quite similar to the parent porphyrin structure. 

NMR spectra show the ethene molecules to undergo a propeller type rotation about the metal-alkene axis the fluxionality is removed on cooling such rotation is not observed with coordinated C2F4, indicating a higher barrier to rotation, in keeping with the stronger Rh—C bonds [66]. 

The 13C-NMR spectra of 4-7, 9-11 show a close similarity to the spectral data of analogous carbene complexes. The shift differences between the metal carbonyls of the silylene complexes and the related carbon compounds are only small. These results underline the close analogy between the silicon compounds 4-7, 9-11 and Fischer carbene complexes. This view is also supported by the IR spectral data. On the basis of an analysis of the force constants of the vco stretching vibration,... 

Proton noise decoupled 13C-NMR spectra of equimolar mixtures of the cyclic hexamer and metal thiocyanates showed that the signals of the carbonyl carbon and two methine carbons gave downfield shifts upon the addition of metal thiocyanates, while those of the three methylene carbons of the tetrahydropyran ring gave upfield... 

It is worth noting, prior to citing actual metal atom studies, the recent secondary ion mass spectrometry (SIMS) on an argon matrix-isolated propene sample, demonstrating the applicability of SIMS analysis to the characterization of matrix-isolated species. The same group h s reported the first C NMR spectra of organic molecules trapped in an argon matrix. ... 

The unfused cyclobutadiene system is stable in complexes with metals (see Chapter 3), but in these cases electron density is withdrawn from the ring by the metal and there is no aromatic quartet. In fact, these cyclobutadiene-metal complexes can be looked upon as systems containing an aromatic duet. The ring is square planar, the compounds undergo aromatic substitution, and NMR spectra of monosubstituted derivatives show that the C-2 and C-4 protons are equivalent. ... 

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