Cerium IV Complexes

While the investigation of Ce(IV) organyl [152] and alkoxide compounds [153] has attracted some attention, Ce(IV) amide chemistry was investigated in detail 

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An opportunity to use the thermodynamic cycle shown in Fig. 7 was provided by the requirement to estimate stability constants for cerium(IV) complexes of a series of hydroxypyridinones. As stability constants for their cerium(III) analogues had been measured and F °(Ce /Ce ) values established, stability constants for one bidentate and two tetradentate 3-hydroxy-2-pyridinones could be obtained. Log P4 for the former was calculated to be 40.9, log P2 for the complexes of the tetradentate ligands 40.6 and 41.9. These very high values, expected for a 4+ cation, are paralleled by high pCe values between 37 and 38 for the tetradentate ligands (147). 

Th(PhCOCHCOPh)4 has been reported as being isomorphous with the corresponding protactinium(IV), uraniumflV) and cerium(IV) complexes the coordination geometry in the last is a triangular faced dodecahedron, but a more recent publication73 reports the coordination geometry of the uranium(IV) compound as square antiprismatic. 

Since the pioneering work of Kirin et al. [5] various lanthanide(III) and cerium(IV) complexes containing phthalocyanine ligands have been synthesized (Table 17) [213-221]. Equations 15a,b give typical methods of preparation for Ln(III) derivatives. 

Lanthanide(III) catecholates exhibit a complex coordination chemistry in aqueous solution [154], While at neutral pH, 1 1 complexes are present in solution, higher pH values (pH > 11) favor 2 1, 3 1 and 4 1 catechol metal stoichiometries as shown in Na[Gd(cat)2] 10H2O , Na6[Ln(cat)3]2-20H2O (Ln = Gd, Ho) and Na5[Gd(cat)4] 19.2H20. The latter monogadolinium complex is isomorphous with the cerium(IV) complex (Table 11). The change of the metal charge from Ln(IV) to Ln(III) now requires a fifth sodium cation which is disordered over several sites in the cell. 

There was known an isolated case of electron transfer bands in the lanthanides in the form of the yellow to red colours of many cerium(IV) complexes, including43 orange CeClg2 and purple (rapidly decomposing) CeBrf72. However, these bands did not seem to constitute a perfect analogy to the uranyl ion, because they are several hundred times as... 

Among the various cerium(IV) complexes, cerium(IV) ammonium nitrate (CAN) is the most important oxidant in organic synthesis, since it is sufficiently stable in different solvents and is commercially available. Besides its propensity of introducing and removing protecting groups via single-electron transfer or Lewis acid catalysis... 

Purex process, 941 Cerium(III) complexes cerium(IV) system water cleavage, 495 peptides hydrolysis, 425 Cerium(IV) complexes peptides hydrolysis, 425 Cerium-144 recovery, 959... 

Since about 40% of R in minerals of the lighter lanthanides (large ionic radii) is cerium, it early attracted interest to remove the large majority of cerium in a simple process. Bromate oxidizes Ce(III) to a precipitate in solutions buffered by the reactive, but only slightly soluble base calcium carbonate. Ethers can extract ah orange cerium(IV) complex from nitric acid. Concentrates with minor amounts of other R can be recrystallized as (NH4)2Ce(N03). ... 

The reaction of cerium(iv) complexes with phosphine has been investigated. Halide complexes are reduced at least ten times faster than sulphate or perchlorate analogues. There is no direct reaction between the oxidant and phosphine, and the reaction... 

Figure 3 shows a transmission electron micrograph of the same sample, in which needle-like crystallites can be identified, not present in samples that did not present the extra peaks in the X-ray difffactogramme. It is clear that the two are correlated, and it is suggested that the new phase represents an aniline-cerium (IV) complex that precipitates out under the specific synthesis condition. Calcination of the sample leads to elimination of the phase. This phase, presumably, does not contribute significantly to the overall surface area of the sample due to its relatively large particle size, and may, in part, explain the values in Table 1. 

Spec determination of the colored complex in a phosphoric acid medium Spec A = 513 nm of the red-colored radical cation formed upon the reaction of PPP with cerium(lV) in a phosphoric acid medium Spec titration of the cerium (IV) complex (pH = 8 to 10)... 

The octaethylporphryin cerium(IV) complex provides a contrasting case to simple metalloporphyrins because the structure now consists of a cerium(IV) ion... 

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