Rare earth metal coordination chemistry

Rare-Earth Metals Coordination Chemistry of the Periodic Table s Footnotes ... 

Of course, valence electron concentration is not only related to the metal atoms but also to the number and valence of the ligands. Ligand deficiency creates vacant coordination sites at metal atoms and results in cluster condensation, which is the fusion of clusters via short M-M contacts into larger units ranging from zero- to three-dimensional. The chemistry of metal-rich halides of rare earth metals comprises both principles, incorporation of interstitial atoms and cluster condensation, with a vast number of examples [22, 23]. 

The rare-earth metals are of rapidly growing importance, and their availability at quite inexpensive prices facilitates their use in chemistry and other applications. Much recent progress has been achieved in the coordination chemistry of rare-earth metals, in the use of lanthanide-based reagents or catalysts, and in the preparation and study of new materials. Some of the important properties of rare-earth metals are summarized in Table 18.1.1. In this table, tm is the atomic radius in the metallic state and rM3+ is the radius of the lanthanide(III) ion in an eight-coordinate environment. 

Chart 6 Structurally characterized coordination modes of the [AlMe4]-fragment in organo-rare-earth metal chemistry... 

Figure 3.2S The structure of (a) [Dy(H20)(DTPA)] and (b) [Dy2(DTPA)2] [Dy, black (large balls) O, grey N, black (small balls) C, white H, omitted)]. (Redrawn from the CIF files of J. Wang et al, Syntheses and structural determinations of the nine-coordinate rare earth metal Na4[Dy "(dtpa)(H20)]2 l6H20, Na[Dy "(edta)(H20)3]-3.25H20 and Na3[Dy (nta)2(H20)]-5.5H20, Journal of Coordination Chemistry, 60 (20), 2221-2241, 2007 [106] and Y. Inomata, T. Sunakawa and F.S. HoweU, The syntheses of lanthanide metal complexes with diethylenetriamine-N, N, N, N", N"-pentaacetic acid and the comparison of their crystal structures, Journal of Molecular Structure, 648 (1-2), 81-88, 2007 [107].)...

The silyl amide type ligands have been used extensively in rare earth chemistry, as well as in actinide and transition metal chemistry, to stabilize electronically unsaturated metal centers due to the available lone pair on the nitrogen donor atom. Because of the relatively larger steric encumbrance, the rare earth complexes with silyl amide type ligands often exhibit low coordination numbers. As a consequence, the large and electropositive rare earth metal centers are accessible to external reagents, which make them more active in many reactions. 

Phosphoraniminato complexes are presented not only because of their synthetic and structural aspects but also because of their potential application as catalysts, in particular the complexes with transition and rare earth metals. An interesting and extended review covers the coordination chemistry of imino — P(V), aza-P(V) and imino-aza- P(V) ligands. A new one-pot synthesis has been reported for the preparation of Me3SiNPCl3 starting with the reaction of PCI3 and LiN(SiMe3)2 and followed by oxidation with S02Cl2. ... 

This volume of the Handbook on the Physics and Chemistry of Rare Earths adds five new chapters to the science of rare earths, compiled by researchers renowned in their respective fields. Volume 34 opens with an overview of ternary intermetallic systems containing rare earths, transition metals and indium (Chapter 218) followed by an assessment of up-to-date understanding of the interplay between order, magnetism and superconductivity of intermetallic compounds formed by rare earth and actinide metals (Chapter 219). Switching from metals to complex compounds of rare earths, Chapter 220 is dedicated to molecular stmctural studies using circularly polarized luminescence spectroscopy of lanthanide systems, while Chapter 221 examines rare-earth metal-organic frameworks, also known as coordination polymers, which are expected to have many practical applications in the future. A review discussing remarkable catalytic activity of rare earths in site-selective hydrolysis of deoxyribonucleic acid (DNA) and ribonucleic acid, or RNA (Chapter 222) completes this book. 

Aryls Alkyl Homogeneous Catalysis The Electronic Stmcture of the Lanthanides Variable Valency Solvento Complexes of the Lanthanide Ions Lanthanides Coordination Chemistry The Divalent State in Solid Rare Earth Metal Halides Lanthanides Comparison to 3d Metals Trivalent Chemistry Cyclopentadienyl Tetravalent Chemistry Organometallic Organic Synthesis. 

Siloxide ligands are able to coordinate to rare earth metals in various oxidation states and coordination numbers to primarily form mono- and dinuclear complexes. In particular, the synthetic and stmctural chemistry of trivalent rare earth siloxides are well documented in the literature and show analogies with rare earth alkoxides. It is fair to state, however, that the field of divalent and tetravalent rare earth siloxides is poorly developed and that applications pertaining to the design of siloxide-based homogeneous and heterogeneous rare earth metal catalysts as well as the development of novel silicate-based materials are scarce. Although the few results of the catalytic activity of some of the rare earth siloxides in olefin... 

Lanthanides in Living Systems Lanthanides Coordination Chemistry Lanthanides Luminescence Applications Lmninescence Lanthanides Magnetic Resonance Imaging Lanthanide Oxide/Hydroxide Complexes Carboxylate Lanthanide Complexes with Multidentate Ligands Rare Earth Metal Cluster Complexes Supramolecular Chemistry from Sensors and Imaging Agents to Functional Mononuclear and Polynuclear Self-Assembly Lanthanide Complexes. 

Two kinds of salen-type Schiff-base ligands, conjugated and flexible, have been used in the synthesis of polynuclear lanthanide complexes and lanthanide coordination polymers Lanthanides Coordination Chemistry, Rare Earth Metal Cluster Complexes. The stoichiometry and structures of these complexes are dependent on the Schiff-base... 

Thus, the stmctural chemistry of reduced rare-earth metal cluster complexes may be described in a way similar to silicates—where [SiOJ tetrahe-dra share common vertices—or like (anti-)Werner complexes that are either monomers, oligomers, or developed into coordination polymers of various dimensionalities. 

This chapter summarized recent advances in the reduction chemistry of rare earth metals and described our own efforts in synthesizing inverse sandwiches of rare earth arene complexes using ferrocene-based diamide ligands. Unprecedented molecules were synthesized and their unusual electronic structures were studied. Highlights included the synthesis of the first scandium naphthalene complex and its reactivity toward P4 activation and the isolation and characterization of a 6-carbon, lOTi-electron aromatic system stabilized by coordination to rare earth metals. The reactivity of those complexes was also discussed. 

For the coordination chemistry of fluorenyl hgands in rare-earth metal complexes, see Kirillov, E., SaUlard, J.-Y, Carpentier, J.-F. Gronp 2 and 3 metal complexes incorporating fluorenyl hgands. Coord. Chem. Rev., 249,1221-1248 (2005). 

Protonic initiation is also the end result of a large number of other initiating systems. Strong acids are generated in situ by a variety of different chemistries (6). These include initiation by carbenium ions, eg, trityl or diazonium salts (151) by an electric current in the presence of a quartenary ammonium salt (152) by halonium, triaryl sulfonium, and triaryl selenonium salts with uv irradiation (153—155) by mercuric perchlorate, nitrosyl hexafluorophosphate, or nitryl hexafluorophosphate (156) and by interaction of free radicals with certain metal salts (157). Reports of "new" initiating systems are often the result of such secondary reactions. Other reports suggest standard polymerization processes with perhaps novel anions. These latter include (Tf)4Al (158) heteropoly acids, eg, tungstophosphate anion (159,160) transition-metal-based systems, eg, Pt (161) or rare earths (162) and numerous systems based on tri flic acid (158,163—166). Coordination polymerization of THF may be in a different class (167). 

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