Trivalent promethium

Trivalent yttrium and lanthanide metals, except for promethium, have been complexed to octaethylporphyrin by heating at 210 °C in an imidazole melt.17 The complexes obtained as hydroxides, Mm(OEP)(OH), are unstable in acidic media. As the charge radius ratio rule predicts, the early lanthanide metalloporphyrins, MIU(OEP)(OH) (M = La, Ce, PR, Nd), are demetallated during purification, and the middle series (M = Sm, Eu, Gd, Tb, Dy) in 1 % acetic acid in methanol, while the last five (M = Ho, Er, Tm, Yb, Lu) survive in 2% acetic acid in methanol but are dissociated in dilute hydrochloric acid. The Mnl(OEP)(OH) appears to coordinate more than one equivalent of pyridine and piperidine, and dimerizes in noncoordinating solvents such as benzene and dichloromethane at 10 4 M concentration. The dimer is considered to be a di-p-hydroxo-bridged species, different from the p-oxo dimer, Scin(OEP) 20 (Scheme 6). 

Since tropolones and 3-hydroxy-4-pyrones are taken in this chapter to be enols, we now cite their binding as enolato ligands to lanthanum and all the other trivalent lanthanides (save the radioactive promethium) " " . Likewise, we note such studies for complexes with enolato ligands derived from 3-acetyl-4-hydroxycoumarin, dehydroacetic acid and their oximes, and with the aromatic enediolates, squarate and croconate. Periodic trends in thermodynamic parameters were reported and analyzed in these studies. 

The value of performing intermultiplet spectroscopy has been demonstrated by optical results on ionic systems. Well defined atomic spectra from intra-4f transitions have been measured up to 6 eV in all the trivalent lanthanides (except, of course, promethium) [Dieke (1968), Morrison and Leavitt (1982) see fig. 1 based on Carnall et al. (1989)]. Each level is characterised by the quantum numbers L, S, J, F), where L and 5 are the combined orbital and spin angular momenta of the 4f electrons participating in the many-electron wavefunctions, and J is the vector sum of L and 5. The quantum number F represents the other labels needed to specify the level fully. It is usually the label of an irreducible representation of the crystal field and we shall omit it. The Coulomb potential is responsible for separating the 4f states into Russell-Saunders terms of specific L and S, while the spin-orbit interaction is diagonal in J and so splits these terms into either 25-1-1 or 2L -I-1 levels with 7 = L - 5 to L -f 5. Provided the spin-orbit interaction is weaker than the Coulomb interaction, as is the case in the lanthanides, the resulting levels consist of relatively pure L, 5, J), or in spectroscopic notation states. These 27-1-1 manifolds are then weakly... 

Fig. 6. The boiling points and heats of sublimation at 25 C of the lanthanide metals as a function of the atomic number. (After Beaudry and Gschneidner 1978.) The values of promethium were estimated (Beaudry and G schneidner 1978). The open squares for the heats of sublimation are for the trivalent solid metals (with 4f configuration), which vaporize to a gas with the 4f"5d6s configuration the open triangles are for the divalent solid metals (with a 4f" configuration) which vaporize to a gas with the 4f 6s configuration and the solid circles are for trivalent solid metals (4f") vaporizing to a gas with a 4f 6s state.

From the consistency of the difference between the experimental values and A ni,iv it is possible to estimate rather accurately the XPS binding energy of the f level in hypothetically trivalent europium metal. The value one obtains is 6.1 +0.2eV. This value might be useful for considerations of chemical shifts in compounds where Eu is trivalent. For promethium the corresponding XPS binding energy can also be estimated and is found to be 4.9 0.2 eV. 

In conventional neutron spectroscopy of CF levels (Fulde and Loewenhaupt 1986) we are dealing with transitions within the ground-state J multiplet, so-called intramultiplet transitions. As is well known, J multiplets exist at energies above that of the ground-state 7-multiplet. The value of performing intermultiplet spectroscopy has been demonstrated by optical results on ionic systems. Well-defined atomic spectra finm inter-4f transitions have been measured up to 6 eV in all trivalent lanthanides, except promethium, and these are illustrated up to 2 eV in fig. 6. A complete review of both the experiments (up to 1990) and theory has recently been given by Osborn et al. (1991) and the reader is referred to this for more details. In this section we shall summarize the salient points needed to interpret the experiments. 

The base-free compounds of CpjLn type are known for all metals of the being considered block including radioactive promethium (Table III.3.). The cyclopentadienyl complexes of trivalent Sc, Y, La, Ce, Pr, Nd, Sm and Gd prepared in 1954 by Wilkinson and Birmingham in the reaction of anhydrous metal chlorides with CpNa were the first REM organoderivatives [119]. Later this method has been modified and applied to Eu, Tb, Dy, Ho, Er, Tm, Yb and Lu [88, 91, 120, 121]. Up to now it remains to be the main way to the tricyclopentadienyl REM complexes. Besides CpNa, cyclopentadienides or substituted cyclopentadienides of lithium and potassium are used in these reactions [31,95, 100,101, 111, 116] ... 

The trivalent state of americium is the stable aqueous oxidation state. Although americium is the homolog of europium, the Am " radius (0.975 A) is closer to that of Nd " " (radius 0.983 A) [76]. It is a convenient rule of thumb that the radii of the light lanthanide ions are nearly identical to the radii of the corresponding actinides shifted three elements to the right in the periodic table, e.g. r(La " ) a r(U ). In some early purification schemes, fission-product promethium accompanied americium. Am(iii) is precipitated by hydroxide, fluoride, phosphate, and oxalate ions from aqueous solution. 

The trivalent lanthanide metals include lanthanum(III) through lutetium(III). The lanthanide oxides have a variety of uses from semiconductors, glasses, solid-state lasers and catalysts. There is quite a difference in the extent to which the hydrolysis reactions of the lanthanide metals have been studied. Typically, the light lanthanides have been studied to a greater extent than the heavier lanthanides. Neodymium(III) has received the most attention due to the perception that it can be used as an analogue for the trivalent actinide metals, in particular, americium (III). All of the isotopes of promethium are radioactive. 

Klungness and Byrne (2000) studied all of the trivalent lanthanide metals, except for promethium. For each lanthanide, they obtained data at 0.1 and 0.7 moll NaClO and 25 °C and at temperatures of 40 and 55 °C for the higher ionic strength. Ciavatta and co-workers studied the hydrolysis of many of the lanthanide metals at relatively high ionic strength in perchlorate media (either... 

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