Lanthanide complexes nitrato

Using 15N NMR spectroscopy, lanthanide complexation with nitrate in aqueous methanol, and aqueous acetone, the formation of mononitrato, bisnitrato complexes of Er(III), [Ce(NC>3)]2+, [Ce(N03>2]+, tetranitrato, either penta- or hexanitrato complexes were detected. It is significant that [Ce(N03>3] could not be detected and that the nitrato complexes are not formed sequentially [132]. 

Oxyanions form both inner- and outer-sphere complexes in aqueous solutions with lanthanide ions but the number of genuine solid complexes is small. The structures of some nitrato complexes has been elucidated in Chapter 5 dealing with structural chemistry of lanthanide complexes. 

Complexes between HDBP and lanthanides have also been observed, but their low solubility leads to third phases observed at low acidity (containing several species with different chemical forms) (133). During electron irradiation of the TBP/ dodecane/3 mol L 1 HN03 system, Guedon et al. (129) observed the precipitation of Fe(DBP)3 for high concentrations of HDBP (>3 g L1), The formation of complexes between nitrato-nitrosyl ruthenium and HDBP-H2MBP mixtures has also been suggested (103). 

Classes of nitrato complexes formed by lanthanide elements [ 155]. 

B. P. Hay, Inorg. Chem., 30, 2876 (1990). Extension of Molecular Mechanics to High-Coordinate Metal Complexes. Calculation of the Structures of Aqua and Nitrato Complexes of Lanthanide(III) Metal Ions. 

The oxidation state iv is firmly established only for Ce, Pr, and Tb, though the preparation of complex fluorides containing Nd(iv) and Dy(iv) has been claimed. The only lanthanide ion stable in aqueous solution is Ce , and this is probably always present in complexes, as in the nitrato complex in (NH4)2 [Ce(N03)g] (p. 664), The only known binary solid compounds of these elements in this oxidation state are ... 

The solution behavior of the [Ln(BuL)8](N03)3 complexes, however, is not in agreement with what one would expect for an ionic compound. In nitromethane the complexes are nonconducting, indicating covalent, rather than ionic, nitrate groups, while in DMF the compounds are 1 2 electrolytes. This indicates that the nitrato groups are bonded to the lanthanide ion in the same manner as in the [Ln(BuL)3(N03)3] series. Further evidence for the covalency of the nitrate ion in solution is obtained from the solution spectra of these complexes represented in Fig. 3. 

There are other examples where scandium more closely follows the d-type transition metals (or large trivalent metals of the p-block) than the lanthanides. For instance, SUber and Mioduski (1984) found recently that in aqueous methanol this is the case with Sc " " though not with Y +, which resembles La + in its coordination behavior. Furthermore, scandium strongly prefers octahedral coordination in its inorganic complexes (Valkonen, 1979) the maximum CN appears to be 9, which has been achieved only in the case of compact nitrato ligands (see section 6). This may be compared with the lighter lanthanides where 9 is the most common CN and values up to 12 are not rare (cf., section 1.4.2). 

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