Thermal decomposition of 10-molybdo-2-vanadosilicic heteropolyacid:29Si and51V-NMR study

Thermal decomposition of 10-molybdo-2-vanadosilicic heteropolyacid has been studied by²⁹Si and⁵¹V-NMR method.²⁹Si-NMR MAS spectra of solid samples indicate that the HPA begins to decompose at T<300°C and the decomposition is complete at 300–400°C.

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²⁹Si ⁵¹V Si–Mo-V () 12- . ²⁹Si MAS , 300°C 300–400°C.

     

Studies of vanadium catalysts for sulfur dioxide oxidation by51V-NMR

Studies of the⁵¹V-NMR spectra of a series of industrial catalysts and systems modelling the active catalyst component indicate that the catalyst composition depends on the preparation method and during thermal treatment the support interacts with the active component. The local environment of vanadium is being formed in the process of catalytic reactions.

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⁵¹V , -I-4, , : KVO₃, KVO₃–SiO₂, KVO₃–K₂SO₄ , , . .

     

29Si and 13C NMR spectra of permethylpolysilanes

²⁹Si, ¹³C and ¹H NMR spectra are reported for the series of linear permethylpolysilanes Me(SiMe₂)_nMe where n = 1 to 6, for the cyclic permethylpolysilanes (Me₂Si)_n where n = 5 to 8, and for a few related compounds. For linear polysilanes the ²⁹Si and ¹³C chemical shifts can be accurately calculated from simple additivity relationships based on the number of silicon atoms in α, β, γ and δ positions. Adjacent (α) silicon atoms lead to upfield shifts in the ²⁹Si and ¹³C resonances, whereas more remote silicon atoms lead to downfield shifts. The ²⁹Si chemical shifts of the polysilane chains are linearly related to the ¹³C shifts of the carbon atoms attached to the silicon. The ²⁹Si and ¹³C resonances of the cyclic silanes deviate from this relationship. Ring current effects arising from σ delocalization are suggested as an explanation for the deviations. Proton-coupled ²⁹Si NMR spectra are reported for Me₃SiSiMe₃ and for (Me₂Si)_n, n = 5 to 7.     

35Cl, 81Br and 127I NQR spectra of cyclopentadienyltitanium halides

NQR spectra of ³⁵Cl, ⁸¹Br and ¹²⁷I in cyclopentadienyltitanium halides Cp_nTiHal_4-n have been studied. Quadrupole coupling constants of the halogen atoms regularly increase with the increasing number of Cp rings in the molecule, which is apparently connected with the decreasing multiplicity of the TiHal bond. A sharp increase in the asymmetry parameters of the iodine atom on introduction of the Cp rings is evidence for an essential desymmetrization of the electron density in the molecule caused by this operation.     

1H- and 13C-NMR spectra of palladium and platinum meso-tetraphenylporphyrins

The ¹H- and ¹³C-NMR spectra of palladium and platinum mesotetraphenylporphyrins (TPP) are reported. PtTPP demonstrates spin-spin coupling between platinum and the pyrrole·β-protons and carbons. There is some evidence for spin-spin coupling between platinum and the pyrrole α-carbons. PdTPP and PtTPP also demonstrate upfield shifting of their pyrrole α-carbon ¹³C-resonances. Structural and electronic arguments are advanced to explain this behaviour.     

Die chromatographische Trennung und Bestimmung von 51Cr, 54Mn, 60Co und 59Fe

Ohne Zusammenfassung     

29Si and 13C NMR spectra of chloro- and fluoro-substituted linear permethylpolysilanes

²⁹Si and ¹³C NMR spectra are reported for the three halopolysilane series Me(SiMe₂)_nCl, Cl(SiMe₂)_nCl and F(SiMe₂)_nF, where n = 2 to 6. Except for the dihalodisilanes (XSiMe₂)₂, data for all of the compounds fit linear relationships based on substituent constants for chlorine or fluorine atoms in the α, β and γ positions. The effects of halogen substitution on ²⁹Si and ¹³C chemical shifts are rapidly attenuated along the polysilane chain, becoming negligible four atoms away from the halogen. The NMR data provide no evidence for long-range electronic transmission from chlorine or fluorine in halopermethylpolysilanes of the type suggested by other workers [1].     

13C-{1H} NMR spectra of episulphide copolymers

Ethylene sulphide-isobutylene sulphide and propylene sulphide-isobutylene sulphide copolymers have been prepared using anionic catalysts and investigated by ¹³C-{¹H} NMR spectroscopy. The carbon-13 NMR spectra are assigned in terms of diad and triad sequences. There is discussion of the effects of mono- or dimethyl substitution in the α, β, γ or δ positions on the chemical shift of the main chain carbon atoms. It has also been shown that for isobutylene sulphide, as for propylene sulphide, under the influence of an anionic catalyst, there is a normal ring opening only at the primary carbon atom.     

13C-NMR spectra of fluorinated molecules using 19F-13C polarization transfer

¹³C-NMR spectra of fluorinated molecules are difficult to observe under conventional broad-band proton decoupling. The large coupling constants involved make polarization transfer between fluorine and carbon, using INEPT or DEPT experiments very effective while broad band fluorine decoupling collapses the multiplet pattern.     

The solid state 13C-NMR and 19F-NMR spectra of some graphite fluorides

The solid state ¹³C nuclear magnetic resonance spectra of fluorinated graphites show two resonances, one of which is assigned to aromatic carbon and the other to aliphatic carbon. The resonances are very broad with the high-field resonance centered at about 35 ppm below tetramethylsilane (TMS) and a low-field resonance centered at about 160 ppm below tetramethylsilane. The high-field resonance is typical of an sp³-like carbon and the low-field resonance is assigned to sp²-like carbons. It is found that the aromatic resonance in graphite decreases with an increase in fluorination of the graphite fluorides examined in this study. The ¹⁹F nuclear magnetic resonance spectra of C₄F and CF₁ each show one resonance. The fluorine resonance in C₄F is 180 ppm above CFCI₃ whereas the fluorine resonance in CF₁ is 55 ppm above CFCI₃. These peaks are in the range for fluorine bonded to aromatic and aliphatic carbons, respectively.     

15N and 17O NMR spectra of some nitrogen- and oxygen-containing polyfluoroaromatic compounds

The effect of substitution of hydrogen by fluorine on the ¹⁵N and ¹⁷O NMR chemical shifts in N-sulphinylarylamines, azoxy- benzenes, C,N-diarylnitrones and aromatic azomethines has been studied. Changes in nitrogen screening are controlled mainly by the radial factor <r^?3>_2p(N), which depends on the electron density on nitrogen, those in oxygen screening — by the two factors, the excitation energy ΔE^?1 and the radial factor <r^?3>_2p(0), which may operate in the same or opposite directions. The ¹⁵N and ¹⁷O NMR spectra of the above compounds did not show any specific effects of perfluorination.     

Die gleichzeitige Bestimmung von 51Cr und 131J in doppelt markiertem Blut

Ohne Zusammenfassung     

13C NMR spectra of some furocoumarins

¹³C NMR spectra of some naturally occurring furocoumarins and derivatives have been examined. The assignment of chemical shifts for all the C atoms has been achieved by using techniques recently reported by Bose et al.     

Steric effects in 29Si and 13C NMR spectra of trimethylsilyl- and alkyl-substituted benzenes

²⁹Si and ¹³C NMR spectra of trimethylsilylbenzenes substituted at different positions by methyl and trimethylsilyl groups were investigated with special reference to steric interactions between the ortho-substituents. The steric effects, as measured by ¹³C and ²⁹Si chemical shifts, are generally smaller in trimethylsilyl- than in t-butyl-substituted compounds. Both nuclei follow the same general trends in the benzene derivatives.     

13C NMR spectra of η3 -allylmanganesetetracarbonyl compounds; structural implications

The ¹³C NMR spectra of η³-allylmanganese tetracarbonyl complexes are consistent with an overall C_s, symmetry and involving a σ_v plane in the Mn(CO)₄ fragment. A dynamic carbonyl interchange process was looked for but the results are inconclusive, however the barrier for this process is certainly greater than 42 kJ/mol. This observation suggests an octahedral type geometry rather than a square pyramid type configuration.     

13C-NMR relaxation studies of alkali metal cryptate complexes

The ¹³C spin-lattice relaxation times (T₁'s) of cryptands [2.1.1], [2.2.1] and [2.2.2] as well as those of the corresponding cryptate complexes with Li⁺, Na⁺, and K⁺ in CDCl₃ and CH₃OH:D₂O (90:10) were measured and the results are interpreted in terms of molecular compression and desolvation effects.     

Electron spin resonance of 136XeF and 84KrF: new results for polycrystalline spectra

ESR spectra of ¹³⁶XeF· and ⁸⁴KrF· in polycrystalline XeF₂, XeF₄ and KrF₂ were carefully analysed to obtain additional information on the structure and dynamic parameters of radical sites. A set of spectra with slightly different magnetic parameters was found in XeF₄ and KrF₂ and attributed to distortion of the local crystalline field in different sites of the matrix. A qualitative correlation between the dispersion of magnetic parameters and “polychromatic” kinetics of radical decay is demonstrated for the first time.     

The 1H and 13C nuclear magnetic resonance and IR adsorption spectra of substituted polymethylferrocenes

The NMR and IR spectra of sym-polymethylferrocenes have been studied. The abnormal shifts observed of the ¹³C signals from the adjacent methyl groups are discussed in terms of spatial interactions between these groups, which cause charge redistribution in the vicinity of the ¹³C nuclei.     

Infrared spectra of FHF− in alkali halides

The bifluoride ion, FHF^?, has been substitutionally isolated within single crystal samples of several different alkali halides. Infrared spectra of these crystals have been studied for sample temperatures down to 8K when half-bandwidths of less than 1 cm^?1 have been observed. (Note that at room temperature ν₃ is observed to have a half-bandwidth of about 40 cm^?1). The frequency shifts and half-bandwidth changes caused by cooling are considered together with the frequency shifts caused by pressures up to 10 k bar.The low temperature spectra clearly indicate that FHF^? is a linear symmetrical ion when substitutionally isolated within alkali halides of either the NaCl or CsCl structure.