Terbium coordination number

The REPO4 structure for the heavier rare earth elements (terbium to lutetium, yttrium, and scandium) belong to the tetragonal system. The coordination number of the central ions is... 

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. 

The lanthanide-nitrate interaction in anhydrous acetonitrile was investigated by means of conductimetry, vibrational spectroscopy, and luminescence measurements which are very sensitive to changes in the first solvation sphere of the metal ion (Bunzli and Choppin 1989). Conductimetiic data on 0.0001-0.01 M solutions of europium or terbium trinitrate in anhydrous acetonitrile indicate that no dissociation occurs. The vibrational spectra show the presence of coordinated acetonitrile and the nitrato group frequencies are consistent with bidentate anions of approximate C2v local symmetry (Bunzli et al. 1978). When the concentration of nitrate is increased, the formation of [R(N03) ] "b species (n>3) is clearly evidenced in the FT-IR spectra (Mabillard 1983). The coordination numbers determined for Nd, Eu, Tb and Er in solutions containing an excess of nitrate are constant (9.9 0.3) and correspond to the formation of pentanitrato [R(N03)5] species, in which the nitrate ions are bonded in a bidentate fashion and which do not contain any coordinated acetonitrile molecule. The strong nitrate/europium interaction is evidenced when water is added to acetonitrile solutions of europium trinitrate. The first two acetonitrile molecules are quantitatively replaced by water molecules, but the replacement of the remaining solvent molecules is difficult to achieve and requires... 

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 bipyridyl chromophore has been extensively used in lanthanide coordination chemistry. In addition to those based on the Lehn cryptand (see Section IV.B.4), a number of acyclic ligands have also employed this group. One such ligand is L17, which binds to lanthanide ions such that one face of the ligand is left open (Scheme 3) (60). As expected, luminescence is extremely weak in water and methanol, but stronger in acetonitrile ( = 0.30, 0.14 for europium and terbium, respectively). In addition, the nature of the counter ion can... 

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]. 

---