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Promethium compounds

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Promethium(III) nitrate, a promethium compound

Promethium compounds are compounds containing the element promethium, which normally take the +3 oxidation state. Promethium belongs to the cerium group of lanthanides and is chemically very similar to the neighboring elements. Because of its instability, chemical studies of promethium are incomplete. Even though a few compounds have been synthesized, they are not fully studied; in general, they tend to be pink or red in color. Treatment of acidic solutions containing Pm ions with ammonia results in a gelatinous light-brown sediment of hydroxide, Pm(OH)3, which is insoluble in water. When dissolved in hydrochloric acid, a water-soluble yellow salt, PmCl3, is produced; similarly, when dissolved in nitric acid, a nitrate results, Pm(NO3)3. The latter is also well-soluble; when dried, it forms pink crystals, similar to Nd(NO3)3. The electron configuration for Pm is 4f, and the color of the ion is pink. The ground state term symbol is I4. The sulfate is slightly soluble, like the other cerium group sulfates. Cell parameters have been calculated for its octahydrate; they lead to conclusion that the density of Pm2(SO4)3·8 H2O is 2.86 g/cm. The oxalate, Pm2(C2O4)3·10 H2O, has the lowest solubility of all lanthanide oxalates.

Unlike the nitrate, the oxide is similar to the corresponding samarium salt and not the neodymium salt. As-synthesized, e.g. by heating the oxalate, it is a white or lavender-colored powder with disordered structure. This powder crystallizes in a cubic lattice upon heating to 600 °C. Further annealing at 800 °C and then at 1750 °C irreversibly transforms it to monoclinic and hexagonal phases, respectively, and the last two phases can be interconverted by adjusting the annealing time and temperature.

Formula symmetry space group No Pearson symbol a (pm) b (pm) c (pm) Z density,
g/cm
α-Pm dhcp P63/mmc 194 hP4 365 365 1165 4 7.26
β-Pm bcc Fm3m 225 cF4 410 410 410 4 6.99
Pm2O3 cubic Ia3 206 cI80 1099 1099 1099 16 6.77
Pm2O3 monoclinic C2/m 12 mS30 1422 365 891 6 7.40
Pm2O3 hexagonal P3m1 164 hP5 380.2 380.2 595.4 1 7.53

Promethium forms only one stable oxidation state, +3, in the form of ions; this is in line with other lanthanides. According to its position in the periodic table, the element cannot be expected to form stable +4 or +2 oxidation states; treating chemical compounds containing Pm ions with strong oxidizing or reducing agents showed that the ion is not easily oxidized or reduced.

Promethium halides
Formula color coordination
number 		symmetry space group No Pearson symbol m.p. (°C)
PmF3 Purple-pink 11 hexagonal P3c1 165 hP24 1338
PmCl3 Lavender 9 hexagonal P63/mc 176 hP8 655
PmBr3 Red 8 orthorhombic Cmcm 63 oS16 624
α-PmI3 Red 8 orthorhombic Cmcm 63 oS16 α→β
β-PmI3 Red 6 rhombohedral R3 148 hR24 695

Bibliography

  • Lavruk︠h︡ina, Avgusta Konstantinovna; Pozdni︠a︡kov, Aleksandr Aleksandrovich (1970). Analytical chemistry of technetium, promethium, astatine and francium. S2CID 94160197.

References

  1. Driscoll, Darren M.; White, Frankie D.; Pramanik, Subhamay; Einkauf, Jeffrey D.; Ravel, Bruce; Bykov, Dmytro; Roy, Santanu; Mayes, Richard T.; Delmau, Lætitia H.; Cary, Samantha K.; Dyke, Thomas; Miller, April; Silveira, Matt; VanCleve, Shelley M.; Davern, Sandra M. (May 2024). "Observation of a promethium complex in solution". Nature. 629 (8013): 819–823. Bibcode:2024Natur.629..819D. doi:10.1038/s41586-024-07267-6. ISSN 1476-4687. PMC 11111410. PMID 38778232.
  2. ^ Lavruk︠h︡ina & Pozdni︠a︡kov 1970, p. 120.
  3. Emsley, J. (2011). Nature's Building Blocks: An A-Z Guide to the Elements. OUP Oxford. p. 429. ISBN 978-0-19-257046-8.
  4. promethium. Encyclopædia Britannica Online
  5. ^ Lavruk︠h︡ina & Pozdni︠a︡kov 1970, p. 121.
  6. Aspinall, H. C. (2001). Chemistry of the f-block elements. Gordon & Breach. p. 34, Table 2.1. ISBN 978-9056993337.
  7. Lavruk︠h︡ina & Pozdni︠a︡kov 1970, p. 122.
  8. Lavruk︠h︡ina & Pozdni︠a︡kov 1970, p. 123.
  9. ^ Chikalla, T. D.; McNeilly, C. E.; Roberts, F. P. (1972). "Polymorphic Modifications of Pm2O3". Journal of the American Ceramic Society. 55 (8): 428. doi:10.1111/j.1151-2916.1972.tb11329.x.
  10. Pallmer, P. G.; Chikalla, T. D. (1971). "The crystal structure of promethium". Journal of the Less Common Metals. 24 (3): 233. doi:10.1016/0022-5088(71)90101-9.
  11. ^ Gschneidner Jr., K.A. (2005). "Physical Properties of the rare earth metals" (PDF). In Lide, D. R. (ed.). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton, FL: CRC Press. ISBN 978-0-8493-0486-6. Archived from the original (PDF) on 2012-09-18. Retrieved 2012-06-20.
  12. Cotton, Simon (2006). Lanthanide And Actinide Chemistry. John Wiley & Sons. p. 117. ISBN 978-0-470-01006-8.
Promethium compounds
Chemical compounds by element
H
Binary H 		He
Li Be B C N O F Ne
Na Mg Al
Al(I) 		Si
Binary Si 		P S Cl Ar
K Ca Sc Ti V Cr Mn Fe
High-valent 		Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd
Pd(III) 		Ag Cd In Sn Sb Te I Xe
Cs Ba * Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra ** Lr Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og
 
* La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb
** Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No
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