Lanthanide metals neodymium samarium

Lanthanum (La) and lanthanide metals neodymium (Nd), samarium (Sm) and lutetium (Lu) as well as yttrium (Y) with pentamethylcyclopentadienyl (// -MesCs = Cp ) and a silicon-bridged bis(tetramethylcyclopentadienyl) (Me4C5-SiMe2-C5Me4 = Me2SiCp"2) ligand have been proved to be excellent and unique hydrosilylation catalysts which exhibit distinctive features in comparison with traditional Group VEEI late-transition metal catalysts" "". ... 

Fluorosulphates of most of the lanthanide elements in the oxidation state iii have been prepared by the action of peroxydisulphuryl difluoride on the anhydrous metal carbonates. The oxides of neodymium, samarium, and europium, however, gave indications of partial reaction with S2O6F2 to form mixtures of fluorosulphate with oxide. The vibrational spectra and structure of the lanthanide fluorosulphates suggested the presence of mixed co-ordination type anions. Fluorescence emission, and vibrational spectra of the europium compound indicated octaco-ordination and the presence of ter- and bi-dentate fluorosulphate groups. 

Complexes between some lanthanides in a low oxidation state and olefins were isolated by W.J. Evans et al. (1978a, 1981b). Cocondensation of lanthanum, neodymium, samarium or erbium metal with butadiene or 2,3-dimethylbutadiene at — 196°C in a metal vaporization reactor produces a brown solid, which can be extracted by toluene and tetrahydrofuran yielding soluble brown products with the empirical formulas R(C4H4)j for R = Nd, Sm, Er, and R[(CH3)2C4H4]2 for R = La, Er. For these complexes the following three formulas have been suggested ... 

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). 

Compounds of divalent samarium, europium, and ytterbium are well-known. In recent years, lower halides of other lanthanides, such as neodymium 48), praseodymium 45, 49, 90), and thulium 4) have been obtained by reducing the trihalide with the metal. The corresponding reaction of thorium tetraiodide with thorium metal has led to the identification of two crystalline forms of Thl2 41, 91) it is unlikely that the Th ", or even Th ", ion is present in Thl2, but like Prl2, which is formulated as Pr " (r)2( ) (2), the compound is probably of the type Th " (r)2(2 ) 41). Certainly one crystal form is diamagnetic 41), suggesting the latter formulation. 

The known structures of the lanthanide and actinide metals are indicated in table 5.01, from which it will be seen that the structures characteristic of the true metals, and particularly the hexagonal close-packed arrangement, are common. Polymorphism, however, is of frequent occurrence among these elements, and plutonium, for example, crystallizes in no fewer than six modifications—the A1 and A2 structures indicated and four others of greater complexity. Praseodymium, neodymium and samarium are of interest in that they possess close-packed structures in which the sequence of layers is... 

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