Using lanthanides

Compared to the rest of the periodic table, the lanthanide elements are less commonly used in research and industry because they are difficult to work with and extract. And for these reasons they are often far more expensive too. Many of the properties of the materials that they are made with can be made with cheaper alternatives. However, there are some specialist applications for the Ln elements. For example, the element neodymium is used in lasers and commercial magnets with very strong magnetic fields, and samarium is used for its magnetic properties. 

Lanthanide phosphorus compounds are used in cathode ray tubes (CRT) that are found in television screens. They re used to give a variety of colors based on the compounds that are present and made with terbium and holmium. For example europium and yttrium compounds make red colors. They re used because of the unique fluorescence and luminescence properties this is what gives them color. 

You may find lanthanides as the flint in cigarette lighters for example, alloys of cerium and iron form a material called auer metal. When it s struck, it 

The actinide elements begin with actinium. Actinium serves as a starting point for the other actinide series elements, which span 14 spaces across the periodic table from actinium to lawrencium. Actinides are more reactive than lanthanides. They form covalent compounds and organometallic complexes. Most of the actinide elements were discovered during development of the nuclear bomb. The set of actinides is represented by the symbol An. 

The radioactivity of some of these elements causes higher reaction rates when binding other molecules. Otherwise, the actinides act almost exactly like regular transition metals (see Chapter 13). However, only a handful of examples exist because they re also typically radioactive and extremely difficult and dangerous to deal with. 

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Although the Lewis acids used as co-reagents in Friedel-Crafts acylations are often referred to as catalysts, they are, in fact, consumed in the reaction, with the generation of strong acids. There has been considerable interest in finding materials which could function as true catalysts. Considerable success has been achieved using lanthanide triflates. ... 

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

The previously discussed conformational study of 3-substituted thietane oxides using lanthanide shift reagents185 corroborates the conclusions derived from other NMR studies and suggests that all rrans-3-substituted thietane oxides prefer an equatorial oxygen conformation when the thietane oxides are bound to shift reagents. 

Metal-catalyzed hydrophosphination has been explored with only a few metals and with a limited array of substrates. Although these reactions usually proceed more quickly and with improved selectivity than their uncatalyzed counterparts, their potential for organic synthesis has not yet been exploited fully because of some drawbacks to the known reactions. The selectivity of Pt-catalyzed reactions is not sufficiently high in many cases, and only activated substrates can be used. Lanthanide-catalyzed reactions have been reported only for intramolecular cases and also sulfer from the formation of by-products. Recent studies of the mechanisms of these reactions may lead to improved selectivity and rate profiles. Further work on asymmetric hydrophosphination can be expected, since it is unlikely that good stereocontrol can be obtained in radical or acid/base-catalyzed processes. 

The lanthanide salts are unique among Lewis acids in that they can be effective as catalysts in aqueous solution.61 Silyl enol ethers react with formaldehyde and benzaldehyde in water-THF mixtures using lanthanide triflates such as Yb(03SCF3)3. The catalysis reflects the strong affinity of lanthanides for carbonyl oxygen, even in aqueous solution. 

Assays based on luminescent lanthanide ions were developed initially in the 1970s, when instrumentation became available which could distinguish long-lived luminescence from a shortlived background. Leif and co-workers reported the first attempts to use lanthanide complexes (in this case europium complexes with 1,10-phenanthroline and 7-diketonates, i.e., [Eu(phen)(diketo-nate)3]) as tags for antibodies.107 These proved kinetically unstable in the pH regime required... 

Hemmila, 1988) (see Chapter 9, Section 9). The most commonly used lanthanides for this purpose are europium (Eu3+), terbium (Tb3+), and samarium (Sm3+). Proteins modified with DTTA and complexed with lanthanide metal ions form the basis for unique fluorescent probes possessing long lived signals upon excitation. 

S. Kobayashi, H. Ishitani, M Ueno, Facile Synthesis of a-Amino Nitriles Using Lanthanide Triflate as a Lewis Acid Catalyst Synlett. 1997,115-116. 

The LIS (Lanthanide Induced Shift) NMR technique is useful for such analysis25 and the separation of olefin enantiomers such as limonene, a-camphene and /J-pinene has been performed upon addition of silver salts such as Ag(fod) or Ag(hfc) to the commonly used lanthanide chiral salts such as Ln(tfc )3 or Ln(hfc)3, where fod = 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyloctanedione, hfc = heptafluoro-3-butyrylcam-phorato and tfc = trifluoroacetylcamphorato. 

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). ... 

The reductive disproportionation of C02 to give CO and C03 , promoted by electron-rich transition metals [9, 101] or to produce C20 using lanthanides such as Sm [102, 103], has been observed in a number of systems. 

Li, C. W., and Korshin, G. V. (2002). Studies of metal-binding sites in natural organic matter and their role in the generation of disinfection by-products using lanthanide ion probes. 

The detection of aromatic carboxylates via the formation of ternary complexes using lanthanide ion complexes of functionalised diaza-crown ethers 30 and 31 has been demonstrated [134]. Like the previous examples, these complexes contained vacant coordination sites but the use of carboxylic acid arms resulted in overall cationic 2+ or 1+ complexes. Furthermore, the formation of luminescent ternary complexes was possible with both Tb(III) and Eu(III). A number of antennae were tested including picolinate, phthalate benzoate and dibenzoylmethide. The formations of these ternary complexes were studied by both luminescence and mass spectroscopy. In the case of Eu-30 and Tb-30, the 1 1 ternary complexes were identified. When the Tb(III) and Eu(III) complexes of 30 were titrated with picolinic acid, luminescent enhancements of 250- and 170-fold, respectively, were recorded. The higher values obtained for Tb(III) was explained because there was a better match between the triplet energy of the antenna and a charge transfer deactivation pathway compared to the Eu(III) complex. 

ROP of lactones and lactides using lanthanide alkoxide-based initiators is a relatively recent discovery. The first example of lactone polymerization by lanthanide alkoxide complexes was reported in a DuPont patent written by McLain and Drysdale in 1991 [89]. In general, the activity of these catalysts is much higher than that determined for aluminum alkoxides, especially in lactide polymerization [90-92]. Polymers of relatively high molecular weight and narrow MWD are formed. The negative side-reactions such as macrocycle formation, transesterification, and racemization are absent. 

Principle of time-resolved luminescence measurement using lanthanide labels 190... 

Some salient points to note are (i) the model is in accord with the experimental results, (ii) nuclei at a and yS positions to the coordinating atom show deviations from the model due to contributions of other shift mechanisms. Thus the best procedure for the elucidation of molecular structure by using lanthanide reagents consists of (i) to obtain the relative magnitude of geometrical function, G for different ligand nuclei from the slopes of A bT versus 1 / T plots, (ii) since temperature dependence of ytterbium complexes conforms to the model, use of ytterbium complexes is prudent, (iii) in cases where the temperature dependence is interfered with effects due to chemical equilibrium or exchange, data for a number of lanthanides at room temperature may be obtained and plots of equation... 

Biological macromolecules studied by X-ray method using lanthanides. 

In the context of replacing conventional Lewis acids in organic synthesis it is also worth pointing out that an alternative approach is to use lanthanide salts [39] that are both water soluble and stable towards hydrolysis and exhibit a variety of interesting activities as Lewis acids (see later). 

Williams, T.H. Naphthomycin, a novel ansa macrocyclic antimetabolite. Proton NMR spectra and structure elucidation using lanthanide shift reagent. J. Antibiotics 28, 85 (1975)... 

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