Praseodymium complexes structure

Diphosphazane dioxide complexes of lanthanides have potential application in the solvent extraction separation of lanthanides. Reaction of lanthanide nitrate with X2P(0)NPr )-P(0)X2(L-L) yields the bis chelate complexes Ln(NC>3)(L-L)2. The structure of the praseodymium complex has been determined by X-ray diffraction and the space group is P32- There are two independent molecules in the unit cell which differ in orientation of the phenyl group. The metal ion is ten-coordinated [264]. 

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... 

Praseodymium, tris(2,2,6,6-tetramethyl-3,5-heptanedione)-photosubstitution, 408 Praseodymium(II) complexes structure, 101... 

Structure and the proton NMR spectrum of a new dimeric praseodymium complex [Pr2(2.2.1)2(011)2]4[0104]-2[CH3CN] whose structure is quite unusual because of the two p-hydroxo bridges that link the two metal ions. The formation of this dimeric species could account for the unexpected affinity of the lanthanide (2.2.1) cryptates for the hydroxyl ion [4]. 

Extensive H NMR studies have been done with the cyclohexyl isocyanide adducts of CpsLn. In the case of the praseodymium complex, while at room temperature rapid inversion of the cyclohexyl ring gives rise to 7 discrete cyclohexyl proton resonances, by lowering the temperature ( 70 C) it has been possible to detect all 13 possible signals for the two slowly inverting conformers (AG for the ring inversion=282 15 cal/mole) (Von Ammon et al. 1971). The electronic structure of CpsLn adducts has been studied by Amberger and Schultze (1987). 

All the hexaisothiocynato complexes of praseodymium to lutetium and yttrium are isostructural. The formula of the lanthanum complex is (GtH LafNCS) but its structure is not known. Since lanthanum is large it may adopt six-coordination less readily. Another example of six-coordination is hexakis antipyrene yttrium(III) iodide whose structure is shown in Fig. 5.7. The antipyrene ligand is large and the six oxygen atoms coordinated to yttrium form an octahedron with S6 molecular symmetry. 

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). 

Figure 3.11 Structures of (a) [Sm2L6(MeOH)4] (HL = benzoic acid) and (b) [Pt2L6(H20)3] (HL = acetic acid) [RE, black O, grey C, white H, omitted]. (Redrawn from the CIF files of U.R Singh, R. Kumar and S. Upreti, Synthesis, structural, photophysical and thermal studies of benzoate bridged Sm(III) complexes, Journal of Molecular Structure, 831 (1-3), 97-105, 2007 [56] and D. Deiters and G. Meyer, Synthesis and crystal structure of praseodymium propionate trihydrate, Pr(CH3CH2C00)3(H20)3, Zeitschrift filr Anorganische und Allgemeine Chemie, 622 (2), 325-328, 1996 [57].)...

---