Lanthanide complexing reagent

N.m.r. studies of coordination complexes using lanthanide shift reagents. L. F. Lindov, Coord. 

Whereas lanthanide triflates are strong Lewis acids, lanthanide complexes such as Yb(fod)3 and Eu(fod)3 are mild catalysts that can be used when the cycloaddition involves acid-sensitive reagents and/or cycloadducts [34]. 

Alternatively, complexation with lanthanide shift reagents allow the signals of the MTPA ester to be resolved and used to determine enantiomeric... 

In addition to these systematic studies of lanthanide sulfoxide complexes, with variation in both sulfoxide and anion, other more isolated reports are available. Lanthanide isothiocyanate complexes of the cyclic sulfoxides thioxane oxide (490) and tetramethylene sulfoxide (493) have been synthesized and complexes of the unusual potentially chelating ligand 2-(ethylsulfinyl)pyridine-V-oxide (63) described. Detailed studies of the solvation of lanthanide-shift reagents by Me2SO have also appeared (178,179). 

Similar differentiation between enantiomers by means of NMR can also be achieved by the use of chiral lanthanide shift reagents (243). Tris-[3-(heptafluoropropylhydroxymethylene)-d-camphorato] -europium was used for the first time (244) for determining the enantiomeric content of benzyl methyl sulfoxide 34. The enantiomeric composition of the partially resolved methyl p-tolyl sulfoxide 41 was estimated using tris-[3-(r-butylhydroxymethylene)-c -camphorato]-europium (245). Another complex of europium, tris-[3-(trifluoro-methylhydroxymethylene)-c -camphorato] europium (TFMC), in contrast to those mentioned above, was effective in the differentiation of various enantiomeric mixtures of chiral sulfinates (107), thiosul-finates (35), and sulfinamides (246). 

Optically pure (3i )(—)-linalyl acetate was detected in the oils of clary sage Salvia sclarea). Salvia dominica, lavender and lavandin using H-NMR spectroscopy with a chiral lanthanide shift reagent, Eu(hfc)3. This enantiomer was also detected in the oils of lavender, lavandin and bergamot using complexation gas chromatography on Ni(hfc) 2, and... 

The very useful lanthanide shift reagents, which facilitate analysis of molecular stereochemistry because of their line-broadening characteristics in NMR spectra, were studied when bound as a chelate complex to thietanes. X-Ray analysis of the adduct 3,3-dimethylthietane 1-oxide with tris(dipivalo-methanato)europium(III) [Eu(dpm)3] revealed the structure of a seven-coordinate complex (271). ... 

Lanthanide shift reagents form short-lived collision complexes with solutes (S) which contain atoms/groups with free electron pairs ... 

Lanthanide shift reagents have been used to differentiate diastereomeric oximes, dinitrophenyl-hydrazones 304,305, and nitrones 306. A collision complex model to rationalize aromatic solvent induced shifts in the spectra of oximes and hydrazones has been developed305,307. 

In the determination of the relative configurations in acyclic diastereomers with the aid of lanthanide shift reagents (LSR), conformation plays a major role and the equilibrium of rotamers in the complex may differ from that of the pure solute. 

Lamture, J. B. Wensel, T. G. A novel reagent for labeling macromolecules with intensely luminescent lanthanide complexes. Tetrahedron Lett. 1993, 34, 4141—4144. 

Studies of complexation with lanthanide shift reagents 1105... 

Under this section are considered lanthanide complexes of /3-diketones and their adducts, but work specifically in the area of lanthanide shift reagents is dealt with in Section 39.2.9. Of course, the majority of lanthanide shift reagents are lanthanide /3-diketonates, and when they function as shift reagents they do so by forming adducts in solution. Furthermore, interest in shift reagents has directly stimulated a considerable amount of fundamental research on lanthanide /3-diketonates and their adducts. Much of this fundamental work was, therefore, carried out in the early 1970s. AH this means that the division between this section and Section 39.2.9 is not entirely clear cut. 

The crystal field does, however, have a dramatic effect on the magnetic anisotropy of lanthanide complexes. For complexes of less than cubic symmetry the three principal values of the susceptibility tensor are unequal. For uniaxial symmetry, Xx — Xy Xz and for biaxial symmetry Xx Xy Xz- Very extensive studies632-640 have been carried out on the single crystal susceptibilities of the D3d lanthanide hexakis(antipyrene) triiodides over the temperature range 80-300 K, and crystal field parameters were obtained. This crystal field-induced anisotropy is responsible for the effectiveness of lanthanide complexes as NMR shift reagents, and single crystal anisotropies of lanthanide complexes have been determined in this connection also.563... 

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