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Coordination-induced shifts

H NMR Chemical and Coordination-Induced Shifts for the Two Protons of the Imidazole Ring in Aqueous Oxobisperoxovanadate Histidine-Derived Complexes of VOL2X Stoichiometry... [Pg.101]

Coordination-Induced Shifts for the H6 proton (CIS — 5, complexed, -5, Free)"... [Pg.188]

The dec helps determine where any given alkene complex lies on the D-C/MCP continuum. The coordination-induced shift of any vinyl protons, or of the vinyl carbons in the and NMR spectra, also shows a correlation with the structure. For example, at the MCP extreme, the vinyl protons can resonate 5 ppm, and the vinyl carbons 100 ppm to high field of their position in the free ligand, owing to change of hybridization from sp to at carbon. Coordination shifts are much lower for the D-C extreme. [Pg.136]

The first applications of lanthanide induced shifts (LIS) in 13C NMR appeared in 1971. (7-10) Shortly thereafter it was shown (11) that Eu(dpm)3 induced chemical shift changes in cholesterol which extended from the coordination site at C-3 clear across the ring system, the assignments used being those of Roberts group. (2) Although the LIS... [Pg.200]

The angular and distance information provided by the lanthanide induced shift has found widespread application from the determination of solution structures of Ln chelates [18,19] to gaining structural information on proteins, nucleotides and amino acids [19], More recently anion binding to coordinatively unsaturated lanthanide complexes has been effectively signalled as the observed lanthanide induced shift has been directly correlated to the nature of the donor atom in the axial position [8,20,21], It is the polarisability of the axial donor that ranks the second order crystal field coefficient, B02, and hence determines the magnitude of the observed shift. Values of the mean shift of the four most-shifted axial protons of the 12-Nq ring for [Yb.la]3+ are collated in Table 2. [Pg.125]

Ethylene-W -diacctic acid (EDDA) and similar ligands form well-characterized octahedral complexes in aqueous solution where C-13 coordination-induced chemical shifts, 51V and nO NMR spectroscopy has been utilized in their study [40], X-ray crystal structure analysis showed formation of the (3-cis isomer, whereas NMR studies clearly showed two complexes in solution. The nO NMR studies [40] were fully consistent with retention of octahedral coordination by both of the isomers, and these two compounds were assigned as the a- and p-cis isomers, which are depicted in Scheme 4.11. The study of these isomers in water (a-cis, -514 ppm 13-... [Pg.57]

Coordination-Induced C-13 Chemical Shifts in Vanadium(V) Dipeptide Complexes... [Pg.67]

There is evidence from Raman studies that oxalate coordinates in a bidentate manner without elimination of a peroxo group [6], Possibly here, as for the picolinate complex, the question of the coordination could be more definitively answered by observation of 13C coordination-induced NMR chemical shifts. The x-ray structure for the oxalate complex shows that the two V0ox bond distances are very different. The VO distance to the equatorial oxalato oxygen is 2.060(4) A compared to 2.251(4) A to the apical oxygen [15], Similarly long distances are found in the picolinato complex (VOpic 2.290 A [16]) and other complexes [20], These distances are indicative of relatively weak bonds to the apical oxygens, and dissociation of that bond... [Pg.105]

Based on these coordination-induced frequency shifts, it may be conjectured that the HREEL spectra in Figs. 14 and 15 are due to a... [Pg.301]

This method of resolution of polyolefins has been extensively studied for cyclooctatetraene systems where excellent enantiomeric excesses are normally observed. Lanthanide-induced shifting can be used to determine the diastereoisomeric composition of the urazoles. Alternate means for the resolution of polyenes based on kinetic resolution using (+)-tetra-2-pinany Iborane have been described, but this reagent consumes valuable substrate. Chiral platinum complexes can also be used but at prohibitive cost on a large scale and with poor regioselec-tivity when several coordination sites are present. [Pg.146]


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See also in sourсe #XX -- [ Pg.304 ]




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Coordination lanthanide-induced shifts

Induced shifts

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