Rare earth metal chelates

Shigematsu, T., Matsui, M., Utsunomiya, K. Gas chromatography of rare-earth-metal chelates of pivaloyltrifluoroacetone. Bull. Chem. Soc. Japan 41, 763 (1968). 

Tanaka, M., Shono, T., Shinra, K. Thermogravimetric analysis and gas chromatography of rare-earth-metal chelates of trifluoroacetylpivaloylmethane (1,1,1 -triflu oro5-5-dimethy 1-hexane-2,4-dione). Anal. Chim. Acta 43, 157 (1968). 

The pH effect in chelation is utilized to Hberate metals from thein chelates that have participated in another stage of a process, so that the metal or chelant or both can be separately recovered. Hydrogen ion at low pH displaces copper, eg, which is recovered from the acid bath by electrolysis while the hydrogen form of the chelant is recycled (43). Precipitation of the displaced metal by anions such as oxalate as the pH is lowered (Fig. 4) is utilized in separations of rare earths. Metals can also be displaced as insoluble salts or hydroxides in high pH domains where the pM that can be maintained by the chelate is less than that allowed by the insoluble species (Fig. 3). 

The beryllium chelate of 2,4-pentanedione is another example of a stable chelate it melts at 108°, boils at 270°, and is soluble in many organic solvents. By replacing the methyl groups of 2,4-pentanedione with rert-butyl groups, a diketone is obtained which, with many metals including transition and rare-earth metals, forms complexes that often are highly soluble in nonpolar organic solvents. The interior of these chelates is saltlike but the exterior is hydrocarbonlike and nonpolar, which accounts for the substantial solubility in nonpolar solvents. 

All currently available extracellular contrast agents are gadolinium chelates. This rare earth metal ion exhibits the strongest effect of all elements on the longitudinal relaxation time Tl. The ligands of these chelates belong to two different types of structure Acyclic (open-chain) compounds and macrocyclics. 

Their capacity to form chelating units having different oxidation states explains a variety of formed coordination compounds [133-136], A series of novel preparative synthetic methods of o-semiquinolate (SQ) and catecholate complexes of transition (Mn, Re, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Ti, Hg), nontransition, and rare-earth metals in various oxidation states and ligand environments has been developed... 

Eppinger, J., Nikolaides, K.R., Zhang-Presse, M. et al. (2008) Alkyl complexes of rare-earth metal centers supported by chelating l,l -diamidoferrocene ligands synthesis, structure, and application in methacrylate polymerization. Organometallics, 27, 736. 

Ligand labeling with fluorescent metal chelates has created a versatile class of fluorescent probes. The chelates of rare earth metals have unique emission characteristics in that, upon excitation of aromatic portions of the ligands of the lanthanide complex, the energy of excitation is efficiently transferred to the lanthanide ion. This causes f-f transitions that produce very narrow almost line-like emission bands that permit all of the emitted light to be collected by the detector with narrow emission slits. In addition, the rare earth... 

Catalyst systems obtained in situ from rare-earth metal trisamides Ln N-(SiMc3)2 3 and various chelating diamines (Fig. 17) have shown good activity in the cyclization of aminoalkenes (Schemes 3 and 4) [123,125-127]. The more challenging cyclization of the chiral aminoalkene 26 can be accomplished with... 

Rare-Earth Metal Postmetallocene Catalysts with Chelating Amido Ligands... 

Keywords Amido ligands Chelates Homogeneous catalysis Rare-earth metals... 

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