Rare Earth Nitrate Compounds

On a qualitative basis, the fluorescence of the napy complexes containing chloride is weaker than that of the corresponding nitrate compounds. Such variation can be ascribed to the difference in coordinating ability of the anion and/or to the amount of coordinated water. Conductivity studies of the nitiate and chloride complexes in nitromethane yield A values of 13-19, which indicates that the complexes are nonelectrolytes (12, 13, 14). The presence of bands attributable to vM-Cl and vM-OH ) in the IR spectra of the chloride complexes substantiates the conclusion that all species are bound to the rare earth ion (12), Vibrational modes indicative of bidentate nitrate and the lack of bands suggesting monodentate nitrate are reported for the rare earth nitrate complexes of napy and 2,7-dmnapy (13,14),... 

Other soluble starting compounds may be used besides the rare earth nitrates. Thus, Komissarova et al. (1970a) have prepared ternary compounds of Sc starting from ScClj and alkali dichromate solutions. 

The catalyst are prepared from aqueous solution of rare earth nitrates, lithium carbonate or lithium hydroxide. The solids are obtained by evaporation to dryness at 110 C-120"C of the solution or suspension in which the rare earth is preciplted as oxalate by oxalic acid (pH - 2) or as hydroxide by ammonia (pH - 9). After heat-treatment at 750 C for 24h we obtain the definite compounds as shown in figure 1. 

R2O3 + 3Se02 — R2(Se03)3 (hydrothermal) Teflon lined steel autoclave T = 180—200° C Rare earth nitrates may serve as initial compounds formation of hydrates possible at low pH hydrogenselenites may form... 

Erbium nitrate [Er(NOj) ] may explode when shocked or at high temperatures. As with other rare-earths, erbium and its compounds should be handled with care because they can be toxic. 

Representative examples of rare earth complexes with halides and pseudohalides are given in Table 4.12. Some oxyanions such as nitrates are included in a separate listing. The formulas given for halide complexes as hexahalides are misleading since these compounds are extended lattice compounds and are not always octahedral. 

The spectra of lanthanide ions are not as sensitive to the environment as the transition metal ions. The small changes in absorption spectra of Eu(NC>3)3 and EuCb were attributed to higher symmetry of the environment in the nitrate compound [128,129]. Later systematic investigations on the band intensities of the rare earth ions were made [130— 135]. The procedure involving an intermediate coupling scheme was used in the calculation of energy levels [123,125]. 

Rare earth /3-diketonate complexes usually are synthesized using the RE chloride and ammonium or sodium /S-diketonate in water or ethanol solvent. Rare earth chlorides are preferred over nitrate or acetates due to the lower coordination power of chloride anion. Binnemans, Mehrotra, Thompson , Joshi and Manas give an overview of the synthesis of rare earth ion complexes with /S-diketonate ligands including different RE +-(1,3-diketonate) coordination compounds. 

For production of uranium compounds suitable for use in nuclear reactors or for isotope separation, further chemical procedures are applied, as indicated in Fig. 11.9. Nuclear purity means that the compounds are free of nuclides with high neutron absorption cross section, i.e. free of boron, cadmium and rare-earth elements. Selective extraction procedures are most suitable for this purpose. Uranyl nitrate hexa-hydrate (U02(N03)2 6H2O UNH) is obtained by concentration of solutions of U02(N03)2, and ammonium diuranate ((NH4)2U207 ADU) by precipitation with ammonia. 

For example, in the determination of the atomic weight of lanthanum the salt lanthanum ammonium nitrate was recrystallized from water 126 times, eadi crystallization involving the separation of die material into as many as 12 fractions. Analysis of the final fraction showed constancy of composition to 1 part in 20,000. Lanthanum compounds, like other rare-earth compounds, are hard to purify because corresponding compounds of the rare-earth metals differ only slightly from one another in properties. 

Films of IVA-VIA compounds have been prepared by the aqueous reactions of group IV nitrates with thio- or selenourea, in basic solution. More recently, bulk crystals, especially of the alloys, have been made by direct reaction. Control of stoichiometry is always difficult. At present, molecular beam epitaxy (precise evaporation of the elements) has become preeminent, because alloys of PbTe with both SnTe and EuTe can be made. It is surprising that a rare earth atom can be substituted into such a lattice, and even more surprising that its electronic behavior appears to be that of a substituent with a valence of + 2. Sn02, while differing widely from the lead salts , is also a IV-VI compound that can be prepared as films by spray pyrolysis of the chloride, or by reactive evaporation or sputtering. 

Pyrazolin-5-ones form complexes with both inorganic and organic compounds much more readily than do the 2-pyrazolin-5-ones. The most extensive series of complexes is that formed with a variety of metallic salts. Antipyrine (2,3-dimethyl-l-phenyl-3-pyrazolin-5-one) forms a series of complexes with salts of divalent, trivalent and tetra-valent metals. Two molecules of antipyrine form a complex with one molecule of copper, cadmium, cobalt and zinc salts.266,866,1116 Complexes prepared from metallic nitrates are usually hydrated.1322 There also exists a series of complexes in which three molecules of antipyrine form a complex with one or two molecules of metallic salts. Such complexes form with two molecules of simple ferric salts272 or with one of complex iron cyanides.608 Nitrates of thorium, lanthanum, cerium and samarium also give such complexes.841 This ratio also occurs in some antipyrine complexes with cadmium and zinc thiocyanate.266 A number of salts of rare earths and iron which have complex anions such as thiosulfate, thiocyanate, dithionic acid and complex iron cyanides form complexes in which six molecules of antipyrine are present.405,408 608,841,950 Stannic chloride forms salts containing three or four molecules of antipyrine and hydrochloric acid.46... 

---