Synthesis applications lanthanides

So far in this section the examples discussed have comprised of hetero aromatic antenna receptors, which mainly function as pH sensors. The detection of metal cations in biological, medical and ecological applications is of major interest. However, this requires more elaborate receptors that can selectively bind a specific metal cation. Naturally, the more elaborate the receptor required, the more challenging its synthesis becomes. The synthesis of lanthanide-based sensors of 53 and 54 has been reported with each ligand incorporating an antenna/receptor selective for zinc(ll) [158,159]. In both cases the receptors are structurally similar, with 53 synthesised from benzylamine and 54 from aniline. 

The discussion below starts with the general synthesis of lanthanide alkoxides, followed by a summary of the OR (R = aliphatic or aryl) coordination modes. Selected examples of complexes will then be presented in order to illustrate the coordination chemistry unique to each class of these ligands (aliphatic alkoxido, aryloxido, and macrocyclic polyaryloxido). Toward the end, catalytic and materials applications of lanthanide alkoxide complexes will be discussed. 

COLLOIDAL SYNTHESIS OF LANTHANIDE ORTHOPHOSPHATE NANOPHOSPHORS FOR BIOLOGICAL APPLICATIONS... 

Huhtinen P, Kivela M, Kuronen O, Hagren V, Takalo H, Tenhu H, Lovgren T, Harma H (2005) Synthesis, characterization, and application of Eu(III), Tb(III), Sm(III), and Dy(III) lanthanide chelate nanoparticle labels. Anal Chem 77 2643-2648... 

Lanthanide-based catalysts, despite finding a lot of application in homogeneous catalysis, can be rather problematic due to the lability of some ligand types and the versatility of their coordination chemistry in the -1-3 oxidation state this makes the controlled synthesis of single-site Ln complexes a quite ambitious goal [92]. McLain and coworkers first demonstrated the high potential of a homoleptic yttrium complex Y(OCH2CH2NMe2)3 as ROP catalyst for the preparation of PLA from rac-lactide and that it promotes a rapid and controlled polymerization... 

Lanthanide-containing porous materials have found many applications in various fields [20-22], They are known as active and selective catalysts for synthesis of higher hydrocarbons (mostly ethane and ethylene) from methane [23], which is of considerable importance for utilizing the reserves of natural gas around the World. Cerium oxide has been employed as a catalyst or as a structural promoter for supported metal oxide catalysts... 

Edelmann FT (1996) Rare Earth Complexes with Heteroallylic Ligands. 179 113 -148 Edelmann FT (1996) Lanthanide Metallocenes in Homogeneous Catalysis. 179 247-276 Effenhauser CS (1998) Integrated Chip-Based Microcolumn Separation Systems. 194 51 - 82 Ehrfeld W, Hessel V, Lehr H (1998) Microreactors for Chemical Synthesis and Biotechnology -Current Developments and Future Applications. 194 233 - 252 Ekhart CW, see de Raadt A (1997) 187 157-186... 

Carboxylates With the aim of developing highly luminescent Er111 complexes for advanced photonic applications, some of the research concentrates on the synthesis of new ligands, based on simple molecular frameworks such as alkyl chains or benzene rings fitted with carboxylate groups for coordination to the lanthanide ions. For instance, the photophys-... 

Asymmetric ate complexes of type Na3Ln((S)-BINOL)3 6THF H20 (Ln = Pr, Nd, Eu) could be crystallized from THF and exist only in the /1-form [158], Their stability against moisture had an enormous impact on application of lanthanide alkoxides in organic synthesis (Sect. 6.2.1). 

Metal rf-inline complexes with various transition metals [1-10] and lanthanides [11,12] are well known in the literature. Early transition metal if-imine complexes have attracted attention as a-amino carbanion equivalents. Zirconium rf-imine complexes, or zirconaaziridines (the names describe different resonance structures), are readily accessible and have been applied in organic synthesis in view of the umpolung [13] of their carbons whereas imines readily react with nucleophiles, zirconaaziridines undergo the insertion of electrophilic reagents. Accessible compounds include heterocycles and nitrogen-containing products such as allylic amines, diamines, amino alcohols, amino amides, amino am-idines, and amino acid esters. Asymmetric syntheses of allylic amines and a-amino acid esters have even been carried out. The mechanism of such transformations has implications not only for imine complexes, but also for the related aldehyde and ketone complexes [14-16]. The synthesis and properties of zirconaaziridines and their applications toward organic transformations will be discussed in this chapter. 

It is a commonplace to say that there has been explosive growth in the use of lanthanides in organic chemistry. For many years, the use of cerium(iv) compounds as oxidants was widespread, but more recently a whole range of other compounds have made their appearance. Thus samarium(ii) compounds are now routinely used as one-electron reducing agents and the use of trifluoromethanesulfonate ( triflate ) salts of scandium and the lanthanides as water-soluble Lewis acid catalysts is widespread. Beta-diketonate complexes and alkoxides have also come into use there are even applications of mischmetal in organic synthesis. 

G. A. Molander, Chem. Rev., 1992, 92, 29 (application of lanthanide reagents in organic synthesis). 

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