Mixed halide effect

The dependence of the principal components of the nuclear magnetic resonance (NMR) chemical shift tensor of non-hydrogen nuclei in model dipeptides is investigated. It is observed that the principal axis system of the chemical shift tensors of the carbonyl carbon and the amide nitrogen are intimately linked to the amide plane. On the other hand, there is no clear relationship between the alpha carbon chemical shift tensor and the molecular framework. However, the projection of this tensor on the C-H vector reveals interesting trends that one may use in peptide secondary structure determination. Effects of hydrogen bonding on the chemical shift tensor will also be discussed. The dependence of the chemical shift on ionic distance has also been studied in Rb halides and mixed halides. Lastly, the presence of motion can have dramatic effects on the observed NMR chemical shift tensor as illustrated by a nitrosyl meso-tetraphenyl porphinato cobalt (III) complex. 

X = Ln, Tl, M = Sn, Pb show that the complexes comprise octahedral [FgM] ions and isolated fluoride ions rather than any seven-coordinate metals. Other tin fluorides have more complex structures, such as the dimeric [Su2F4] ion present in [NH4]4[Sn2F4](N03)2" and in mixed halide complexes, such as Cs2SngBr3Fii which has in the crystal three distinct tin sites, each of which has close contacts with the fluoride ions only." The electronic effects of adduct formation of halides of germanium(IV) and tin(IV) have been reviewed with particular reference to the geometry of the complexes formed. 

The effectiveness of the purification of molten lithium halides by hydrogen halides is appreciably lower than mentioned above [232], This is explained by the fact that molten lithium halides keep the water, which can dissolve in these melts in considerable quantities. Even mixed-halide mixtures retain this property, e.g. the molten KCl-LiCl eutectic keeps the dissolved water strongly at temperatures of the order of 400 °C [179], and bubbling of dry HC1 during an hour does not result in complete removal of H20. 

RAMAN EFFECT AND COMPETITIVE FORMATION OF TETRAHEDRAL MIXED HALIDE COMPLEXES BY IN SOLUTION. 

A1 RAMAN EFFECT AND COMPETITIVE FORMATION OF TETRAHEDRAL MIXED HALIDE COMPLEXES BY Ga + IN SOLUTION, L.A. Wood -ward... 

Numerous lanthanide (III) chloride-bromide systems have been characterized. Again, the changes observed can be understood from radius ratio considerations. Most of these studies have been effected by confining the mixed halides in quartz or... 

THE OPTICAL SPECTRA AND VOLTAMMETRY OF MIXED HALIDE / NITRILE / CARBONYL OSMIUM(III) COMPLEXES. ADDITIVE AND NON-ADOinVE EFFECTS... 

The Optical Spectra and Voltammetry of Mixed Halide/Nitrile/Carbonyl Osmium(lll) Complexes. Additive and Non-Additive Effects G.A. Heath andD.G. Humphrey... 

To high frequency of S Pt) = 214 MHz Including the effect of pH Other bis-diketonates have shifts 4578-4155 ppm Including data on mixed halide complexes Including data on hydrolysis products and [Pt(N02)2(C204)] - Including data on [Pt(SCN)4 (NCS)J -... 

Intramolecular acylations are very common, and the normal conditions involving an acyl halide and Lewis acid can be utilized. One useful alternative is to dissolve the carboxylic acid in polyphosphoric acid (PPA) and heat to effect cyclization. This procedure probably involves formation of a mixed phosphoric-carboxylic anhydride.54... 

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