Ions, NMR

Y3Fe50i2 [7], These complexes have been obtained at 110-120°C, isolated, and studied in the crystalline form and in an aqueous solution. IR spectra suggest that these are monodentate coordinated to the metal ions. NMR data are in accord with an assumption that hydroxy and carboxylate groups attached to the central carbon atom of the citric acid anion are coordinated to the metal cations forming a stable five-membered ring. However, these important data are obtained at conditions that do not correspond to the conditions of the synthesis of precursors. 

Chapter 1 by H.-U. Siehl discusses parallel stable ion NMR spectroscopic and computational studies on various classes of silyl-substituted carbocations. Chapter 2 by K. Komatsu focuses on unusually stable n-conjugated carbocations that are formed as a result of annelation to bicyclic frameworks. 

Solvolytic (Diaz et al., 1970), calculational (Kaufmann et al., 1981), and stable ion NMR spectroscopy (Childs and Varadarajan, 1985) studies indicate that the bishomoantiaromatic cation [73] is unimportant and that the most likely structure for this species is the allylic cation [74],... 

Computed GIAO-NMR chemical shifts were compared with the experimental data when available, and the optimized geometries were compared with the X-ray data if known. The lowest energy annulenium cation derived from 76 and 77 (both cis) was formed by protonation at C-1, and this was in concert with experimental observation of 76H" in superacid media. " The resulting annulenium ions were less delocalized than those via 74 and 75. DFT and stable ion study were also in concert regarding the protonation of 78. The availability of X-ray structures and stable ion NMR data for the dieations and dianions of 78 and 79 enabled comparison with the DFT-optimized structures and GIAO-NMR shifts. 

Cupredoxin fold , 47 95 Cupric fluoride, stereochemistry, 2 20 Cupric ion, exchange with cuprous ion, NMR of, 4 276-277... 

Aramini, J. M. and Vogel, H.J. (1998) Quadrupolar metal ion NMR studies of metalloproteins, Biochemistry and Cell Biology 76, 210-222. 

Geopolymers are useful inorganic aluminosilicate framework compounds which form and harden at room temperature. Both the aluminium and silicon atoms in their structure occupy tetrahedral sites, with charge balance achieved by the presence of hydrated monovalent ions. NMR has been used to study the changes occurring when a potassium sialate geopolymer is heated to high temperatures. The cog positions... 

Problems have been observed when attempting to carry out reactions with either diacid chlorides or half-ester half-acid chlorides when the two carbonyl functions are separated by either two or three carbon atoms. Rearrangement reactions occur with those compounds and so Friedel-Crafts acylation reactions may yield mixtures of products. Optically active methyl 3-methylglutarate was shown to racemize easily Suggested explanations of these effects include the involvement of alkyl diacyloxonium and acyl-oxy-alkoxycarbenium ions. NMR studies have shown that the half methyl ester-half acid chloride from phthalic acid forms the acyloxy-alkoxycarbenium ion very easilyj and that the related ions derived from succinic and glutaric acids can also be generated under stable ion conditions. ... 

Ion NMR X-ray or neutron diffraction and related methods Computer simulation Stokes Law radii from ionic conductivities From ionic conductivities with corrections to Stokes Law... 

Among the 2-naphthalenium ions NMR- C data are available for the 1,2,2,3,4-pentamethyl-substituted cation and for a few hydroxynaphthalenium ions... 

In a rare study of ligand substitution on a transuranic metal ion NMR line-broadening data yield k 29S.2 K) = 980 s Ai/ = 46.6 kJ moP and AS = -31J moP for exchange of the four in the equatorial plane of octahedral [Np04(0H)2] with solvent in aqueous 0.5 mol dm NaOH solution. 

In contrast to the trithiacrown-ether complexes of dialkylthallium-(III) ions, NMR spectra of monothia- and dithia-crown-ether complexes in CD CN give only signals of complex species [R2TI(L)]C104 and those of free ions and uncomplexed crown-ether were very small if present at all. Therefore, K values of monothia- and dithia-crown-ether complexes of dialkylthallium(III) ions are much larger than those of trithiacrown-... 

For ligand nuclei the gyromagnetic ratio Yv is isotropic = yv ajs], W/, and the contribution of the W ion-ligand interaction into the second moment of W ions NMR line is... 

If we assume Lorentzian line shape for the halide ion NMR signal we have Av = (ttT2) , where Av is the line width at half height. 

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