Dysprosium coordination number

The chemical composition of rare earth complexes cannot by itself reveal the coordination number of the central metal ion. There are many complexes containing hydrated water molecules and coordinated water molecules. The nitrilotriacetic acid (NTA) complexes of Pr and Dy have the formulae PrNTA 3H2O and DyNTA 4H2O, respectively. The praseodymium complex is a nine-coordinate system with one molecule of water in the hydrated form [12] and the dysprosium complex is eight-coordinate with two molecules of water of hydration [13]. These structures cannot be predicted from the composition of the complexes. The complex Nd(N03>3 4DMSO is ten-coordinate [14] since the nitrate... 

Similar dimeric structures are also encountered with bromides. In the case of Gd compound, tetramers have been reported containing two non-equivalent Gd3+ ions with formal coordination numbers of 8 and 9. These tetrameric units form the basic building blocks of compounds like [CpiGdBr] resulting in polymeric infinite double chains. The dysprosium compound [Cp2DyCl]oo has also the polymeric structure. The structure [62] of tetrameric [Cp2GdCIU is shown in Fig. 6.5. 

The lanthanide or rare earth elements (atomic numbers 57 through 71) typically add electrons to the 4f orbitals as the atomic number increases, but lanthanum (4f°) is usually considered a lanthanide. Scandium and yttrium are also chemically similar to lanthanides. Lanthanide chemistry is typically that of + 3 cations, and as the atomic number increases, there is a decrease in radius for each lanthanide, known as the lanthanide contraction. Because bonding within the lanthanide series is usually predominantly ionic, the lanthanide contraction often determines the differences in properties of lanthanide compounds and ions. Lanthanide compounds often have high coordination numbers between 6 and 12. see also Cerium Dysprosium Erbium Europium Gadolinium Holmium Lanthanum Lutetium Praseodymium Promethium Samarium Terbium Thulium Ytterbium. 

Scandium trichloride possesses the rhombohedral FeClj-type structure. The trichlorides of lanthanum through gadolinium possess the hexagonal UClj-type structure (Coordination Number of lanthanide CN = 9). Terbium chloride and a-DyCljpossess the orthorhombic PuBtj-type structure (CN = 8), while the trichlorides of yttrium and those of dysprosium ( 5-form) to lutetium possess the monoclinic AlClj-type structure (CN = 6). 

The only complexes of lanthanum or cerium to be described are [La(terpy)3][C104]3 175) and Ce(terpy)Cl3 H20 411). The lanthanum compound is a 1 3 electrolyte in MeCN or MeN02, and is almost certainly a nine-coordinate mononuclear species the structure of the cerium compound is not known with any certainty. A number of workers have reported hydrated 1 1 complexes of terpy with praseodymium chloride 376,411,438), and the complex PrCl3(terpy)-8H20 has been structurally characterized 376). The metal is in nine-coordinate monocapped square-antiprismatic [Pr(terpy)Cl(H20)5] cations (Fig. 24). Complexes with a 1 1 stoichiometry have also been described for neodymium 33, 409, 411, 413, 417), samarium 33, 411, 412), europium 33, 316, 411, 414, 417), gadolinium 33, 411), terbium 316, 410, 414), dysprosium 33, 410, 412), holmium 33, 410), erbium 33, 410, 417), thulium 410, 412), and ytterbium 410). The 1 2 stoichiometry has only been observed with the later lanthanides, europium 33, 411, 414), gadolinium, dysprosium, and erbium 33). 

Lanthanide elements (referred to as Ln) have atomic numbers that range from 57 to 71. They are lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). With the inclusion of scandium (Sc) and yttrium (Y), which are in the same subgroup, this total of 17 elements are referred to as the rare earth elements (RE). They are similar in some aspects but very different in many others. Based on the electronic configuration of the rare earth elements, in this chapter we will discuss the lanthanide contraction phenomenon and the consequential effects on the chemical and physical properties of these elements. The coordination chemistry of lanthanide complexes containing small inorganic ligands is also briefly introduced here [1-5]. 

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