Preparation of Lanthanide Complexes in Acetonitrile

[摘要] The reactions of the lanthanide metals (La, Nd, Eu and Tm) with the high oxidation state fluorides (UF6, MoF6 and WF6) in acetonitrile and the reactions between these four lanthanide metals and the NO+ compounds (NOWF7, NOBF4, NOUF6, NOMoF6 and NOPF6) in acetonitrile are described in this thesis. Some reactions between the acetonitrile solvated lanthanide compounds produced from the oxidation of the lanthanide metals by MoF6 or WF6 and the simple N-donor ligands are also described. These simple ligands are pyridine and trimethylamine which are regarded as weak ligands. The solvated salts [La(NCMe)3][WFx]3, [Nd(NCMe)3][MoF6}3, [Eu(NCMe)3][MoF6]3 and [Eu(NCMe)3][WFx]3 (x=6 or 7) have been prepared from the oxidation of the lanthanide metals by the hexafluorides of tungsten or molybdenum in acetonitrile. These salts are all pale yellow in colour and very prone to hydrolysis. The apparent coordination number of the Ln(III) cations in the complexes is 3, which is low compared with most lanthanide complexes. The reason for this is suggested to be interaction between the Ln(III) cation and the fluoroanions. Uranium hexafluoride is reported to be the strongest oxidizing agent among the three high oxidation state fluorides used in this study. There is, however, no evidence of any reaction occurring between the metals, lanthanum, neodymium, europium and thulium and UF6. Polymerization of acetonitrile and reduction of UF6 takes place instead. Molybdenum hexafluoride reacts with europium metal or bright pieces of neodymium ingot freshly cut in the dry glove box. It does not, however, react with lanthanum, thulium and neodymium powder metals. Tungsten hexafluoride reacts with europium and lanthanum metals which are the most reactive among four lanthanide metals used in this work. All the reactions observed in this work are very slow and occur to a limited extent, therefore, the yields are all rather small. The reactions of the lanthanide metals with the hexafluorides used in the present work are similar to many "d" block elements of the periodic table. It is proposed that the oxide film on the surface of the lanthanide metals plays an important role in the oxidation of the metals, which inhibits their reactions, especially in the case of UF6. The salt NOPF6 reacts with all metals used, NOBF4 reacts only with europium and NOMoF6 reacts only with neodymium, however, NOUF6 and NOWF7 do not react with any of the metals. A number of possible causes for the differences in NO+ salt behaviour are discussed. The compounds [La(NCMe)3] [WFx]3, [Nd(NCMe)3][MoF6]3, [Eu(NCMe)3][MoF6]3, and [Eu(NCMe)3][WFx]3 (x= 6 or 7) react readily with pyridine or trimethylamine in acetonitrile at room temperature to form the insoluble compounds: [La(py)7(NCMe)][WFx]3, [Nd(py)7(NCMe)][MoF6]3 [Eu(py)7(NCMe)][MoF6]3, [Eu(py)7(NCMe)][WFx]3 [La(NMe3)4(NCMe)2][WFx]3, [Nd(NMe3)4(NCMe)2][MoF6]3 [Eu(NMe3)4(NCMe)2][MoF6]3, [Eu(NMe3)4(NCMe)2][WFx]3 x= 6 or 7. The reactions between NOPF6 and pyridine, or trimethylamine in acetonitrile result in the formation of two solids. Their microanalysfs reveal that they are the adducts, NOPF6. 2py and NOPF6. 2NMe3.

[发布机构] University:University of Glasgow

[关键词] Inorganic chemistry