Cerium compounds

Last updated

Cerium compounds are compounds containing the element cerium (Ce), a lanthanide. Cerium exists in two main oxidation states, Ce(III) and Ce(IV). This pair of adjacent oxidation states dominates several aspects of the chemistry of this element. Cerium(IV) aqueous solutions may be prepared by reacting cerium(III) solutions with the strong oxidizing agents peroxodisulfate or bismuthate. The value of E⦵(Ce4+/Ce3+) varies widely depending on conditions due to the relative ease of complexation and hydrolysis with various anions, although +1.72 V is representative. Cerium is the only lanthanide which has important aqueous and coordination chemistry in the +4 oxidation state. [1]

Contents

Halides

Cerium(III) fluoride powder Cerium(III) fluoride.jpg
Cerium(III) fluoride powder

Cerium forms all four trihalides CeX3 (X = F, Cl, Br, I) usually by reaction of the oxides with the hydrogen halides. The anhydrous halides are pale-colored, paramagnetic, hygroscopic solids. Upon hydration, the trihalides convert to complexes containing aquo complexes [Ce(H2O)8-9]3+. Unlike most lanthanides, Ce forms a tetrafluoride, a white solid. It also forms a bronze-colored diiodide, which has metallic properties. [2]

Aside from the binary halide phases, a number of anionic halide complexes are known. Fluoride gives the Ce(IV) derivatives CeF4−8 and CeF2−6. Chloride gives the orange CeCl2−6. [1]

Oxides, sulfides, etc.

Cerium(IV) oxide ("ceria") has the fluorite structure, similarly to the dioxides of praseodymium and terbium. Ceria is a nonstoichiometric compound, meaning that the real formula is CeO2-x, where x is about 0.2. Thus, the material is not perfectly described as Ce(IV). Ceria reduces to cerium(III) oxide with hydrogen gas. [3]

Many nonstoichiometric chalcogenides are also known, along with the trivalent Ce2Z3 (Z = S, Se, Te). The monochalcogenides CeZ conduct electricity and would better be formulated as Ce3+Z2−e−. While CeZ2 compounds are known, they are polychalcogenides with cerium(III): cerium(IV) derivatives of S, Se, and Te are unknown. [3]

Cerium(IV) complexes

Cerium(IV) oxide Cerium(IV) oxide.jpg
Cerium(IV) oxide

The compound ceric ammonium nitrate ("CAN") (NH4)2[Ce(NO3)6] is the most common cerium compound encountered in the laboratory. The six nitrate ligands bind as bidentate ligands. The complex [Ce(NO3)6]2− is 12-coordinate, a high coordination number which emphasizes the large size of the Ce4+ ion. CAN is popular oxidant in organic synthesis, both as a stoichiometric reagent [4] and as a catalyst. [5] It is inexpensive, easily handled. It operates by one-electron redox. Cerium nitrates also form 4:3 and 1:1 complexes with 18-crown-6 (the ratio referring to that between cerium and the crown ether).

Classically CAN is a primary standard for quantitative analysis. [6] [7] Cerium(IV) salts, especially cerium(IV) sulfate, are often used as standard reagents for volumetric analysis in cerimetric titrations. [8]

A white LED in operation: the diode produces monochromatic blue light but the Ce:YAG phosphor converts some of it into yellow light, with the combination perceived as white by the eye. 5 mm Tinted White LED (on).jpg
A white LED in operation: the diode produces monochromatic blue light but the Ce:YAG phosphor converts some of it into yellow light, with the combination perceived as white by the eye.

Cerium(III) and terbium(III) have ultraviolet absorption bands of relatively high intensity compared with the other lanthanides, as their configurations (one electron more than an empty or half-filled f-subshell respectively) make it easier for the extra f electron to undergo f→d transitions instead of the forbidden f→f transitions of the other lanthanides. [9] Cerium(III) sulfate is one of the few salts whose solubility in water decreases with rising temperature. [10]

Ceric ammonium nitrate Ceric ammonium nitrate.jpg
Ceric ammonium nitrate

Due to ligand-to-metal charge transfer, aqueous cerium(IV) ions are orange-yellow. [11] Aqueous cerium(IV) is metastable in water [12] and is a strong oxidizing agent that oxidizes hydrochloric acid to give chlorine gas. [1]

In the Belousov–Zhabotinsky reaction, cerium oscillates between the +4 and +3 oxidation states to catalyze the reaction. [13]

Organocerium compounds

Organocerium chemistry is similar to that of the other lanthanides, often involving complexes of cyclopentadienyl and cyclooctatetraenyl ligands. Cerocene (Ce(C8H8)2) adopts the uranocene molecular structure. [14] The 4f electron in cerocene, Ce(C
8H
8)
2, is poised ambiguously between being localized and delocalized and this compound is also considered intermediate-valent. [15] Alkyl, alkynyl, and alkenyl organocerium derivatives are prepared from the transmetallation of the respective organolithium or Grignard reagents, and are more nucleophilic but less basic than their precursors.. [16] [17]

See also

Related Research Articles

<span class="mw-page-title-main">Berkelium</span> Chemical element, symbol Bk and atomic number 97

Berkelium is a transuranic radioactive chemical element with the symbol Bk and atomic number 97. It is a member of the actinide and transuranium element series. It is named after the city of Berkeley, California, the location of the Lawrence Berkeley National Laboratory where it was discovered in December 1949. Berkelium was the fifth transuranium element discovered after neptunium, plutonium, curium and americium.

<span class="mw-page-title-main">Lanthanum</span> Chemical element, symbol La and atomic number 57

Lanthanum is a chemical element with the symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. It is the eponym of the lanthanide series, a group of 15 similar elements between lanthanum and lutetium in the periodic table, of which lanthanum is the first and the prototype. Lanthanum is traditionally counted among the rare earth elements. Like most other rare earth elements, the usual oxidation state is +3. Lanthanum has no biological role in humans but is essential to some bacteria. It is not particularly toxic to humans but does show some antimicrobial activity.

The lanthanide or lanthanoid series of chemical elements comprises the 15 metallic chemical elements with atomic numbers 57–71, from lanthanum through lutetium. These elements, along with the chemically similar elements scandium and yttrium, are often collectively known as the rare-earth elements or rare-earth metals.

<span class="mw-page-title-main">Terbium</span> Chemical element, symbol Tb and atomic number 65

Terbium is a chemical element with the symbol Tb and atomic number 65. It is a silvery-white, rare earth metal that is malleable, and ductile. The ninth member of the lanthanide series, terbium is a fairly electropositive metal that reacts with water, evolving hydrogen gas. Terbium is never found in nature as a free element, but it is contained in many minerals, including cerite, gadolinite, monazite, xenotime and euxenite.

<span class="mw-page-title-main">Praseodymium</span> Chemical element, symbol Pr and atomic number 59

Praseodymium is a chemical element with the symbol Pr and the atomic number 59. It is the third member of the lanthanide series and is considered to be one of the rare-earth metals. It is a soft, silvery, malleable and ductile metal, valued for its magnetic, electrical, chemical, and optical properties. It is too reactive to be found in native form, and pure praseodymium metal slowly develops a green oxide coating when exposed to air.

<span class="mw-page-title-main">Ceric ammonium nitrate</span> Chemical compound

Ceric ammonium nitrate (CAN) is the inorganic compound with the formula (NH4)2[Ce(NO3)6]. This orange-red, water-soluble cerium salt is a specialised oxidizing agent in organic synthesis and a standard oxidant in quantitative analysis.

<span class="mw-page-title-main">Cerium(III) chloride</span> Chemical compound

Cerium(III) chloride (CeCl3), also known as cerous chloride or cerium trichloride, is a compound of cerium and chlorine. It is a white hygroscopic salt; it rapidly absorbs water on exposure to moist air to form a hydrate, which appears to be of variable composition, though the heptahydrate CeCl3·7H2O is known. It is highly soluble in water, and (when anhydrous) it is soluble in ethanol and acetone.

<span class="mw-page-title-main">Samarium(III) chloride</span> Chemical compound

Samarium(III) chloride, also known as samarium trichloride, is an inorganic compound of samarium and chloride. It is a pale yellow salt that rapidly absorbs water to form a hexahydrate, SmCl3.6H2O. The compound has few practical applications but is used in laboratories for research on new compounds of samarium.

The chemical element nitrogen is one of the most abundant elements in the universe and can form many compounds. It can take several oxidation states; but the most oxidation states are -3 and +3. Nitrogen can form nitride and nitrate ions. It also forms a part of nitric acid and nitrate salts. Nitrogen compounds also have an important role in organic chemistry, as nitrogen is part of proteins, amino acids and adenosine triphosphate.

<span class="mw-page-title-main">Silver compounds</span> Chemical compounds containing silver

Silver is a relatively unreactive metal, although it can form several compounds. The common oxidation states of silver are (in order of commonness): +1 (the most stable state; for example, silver nitrate, AgNO3); +2 (highly oxidising; for example, silver(II) fluoride, AgF2); and even very rarely +3 (extreme oxidising; for example, potassium tetrafluoroargentate(III), KAgF4). The +3 state requires very strong oxidising agents to attain, such as fluorine or peroxodisulfate, and some silver(III) compounds react with atmospheric moisture and attack glass. Indeed, silver(III) fluoride is usually obtained by reacting silver or silver monofluoride with the strongest known oxidizing agent, krypton difluoride.

Iron shows the characteristic chemical properties of the transition metals, namely the ability to form variable oxidation states differing by steps of one and a very large coordination and organometallic chemistry: indeed, it was the discovery of an iron compound, ferrocene, that revolutionalized the latter field in the 1950s. Iron is sometimes considered as a prototype for the entire block of transition metals, due to its abundance and the immense role it has played in the technological progress of humanity. Its 26 electrons are arranged in the configuration [Ar]3d64s2, of which the 3d and 4s electrons are relatively close in energy, and thus it can lose a variable number of electrons and there is no clear point where further ionization becomes unprofitable.

<span class="mw-page-title-main">Cerium</span> Chemical element, symbol Ce and atomic number 58

Cerium is a chemical element with the symbol Ce and atomic number 58. Cerium is a soft, ductile, and silvery-white metal that tarnishes when exposed to air. Cerium is the second element in the lanthanide series, and while it often shows the oxidation state of +3 characteristic of the series, it also has a stable +4 state that does not oxidize water. It is also considered one of the rare-earth elements. Cerium has no known biological role in humans but is not particularly toxic, except with intense or continued exposure.

<span class="mw-page-title-main">Thorium compounds</span> Any chemical compound having at least one atom of thorium

Many compounds of thorium are known: this is because thorium and uranium are the most stable and accessible actinides and are the only actinides that can be studied safely and legally in bulk in a normal laboratory. As such, they have the best-known chemistry of the actinides, along with that of plutonium, as the self-heating and radiation from them is not enough to cause radiolysis of chemical bonds as it is for the other actinides. While the later actinides from americium onwards are predominantly trivalent and behave more similarly to the corresponding lanthanides, as one would expect from periodic trends, the early actinides up to plutonium have relativistically destabilised and hence delocalised 5f and 6d electrons that participate in chemistry in a similar way to the early transition metals of group 3 through 8: thus, all their valence electrons can participate in chemical reactions, although this is not common for neptunium and plutonium.

Cerium(III) iodide (CeI3) is the compound formed by cerium(III) cations and iodide anions.

<span class="mw-page-title-main">Aluminium compounds</span>

Aluminium (or aluminum) combines characteristics of pre- and post-transition metals. Since it has few available electrons for metallic bonding, like its heavier group 13 congeners, it has the characteristic physical properties of a post-transition metal, with longer-than-expected interatomic distances. Furthermore, as Al3+ is a small and highly charged cation, it is strongly polarizing and aluminium compounds tend towards covalency; this behaviour is similar to that of beryllium (Be2+), an example of a diagonal relationship. However, unlike all other post-transition metals, the underlying core under aluminium's valence shell is that of the preceding noble gas, whereas for gallium and indium it is that of the preceding noble gas plus a filled d-subshell, and for thallium and nihonium it is that of the preceding noble gas plus filled d- and f-subshells. Hence, aluminium does not suffer the effects of incomplete shielding of valence electrons by inner electrons from the nucleus that its heavier congeners do. Aluminium's electropositive behavior, high affinity for oxygen, and highly negative standard electrode potential are all more similar to those of scandium, yttrium, lanthanum, and actinium, which have ds2 configurations of three valence electrons outside a noble gas core: aluminium is the most electropositive metal in its group. Aluminium also bears minor similarities to the metalloid boron in the same group; AlX3 compounds are valence isoelectronic to BX3 compounds (they have the same valence electronic structure), and both behave as Lewis acids and readily form adducts. Additionally, one of the main motifs of boron chemistry is regular icosahedral structures, and aluminium forms an important part of many icosahedral quasicrystal alloys, including the Al–Zn–Mg class.

Praseodymium compounds are compounds formed by the lanthanide metal praseodymium (Pr). In these compounds, praseodymium generally exhibits the +3 oxidation state, such as PrCl3, Pr(NO3)3 and Pr(CH3COO)3. However, compounds with praseodymium in the +2 and +4 oxidation states, and unlike other lanthanides, the +5 oxidation state, are also known.

Einsteinium compounds are compounds that contain the element einsteinium (Es). These compounds largely have einsteinium forming in the +3 oxidation state, although they can also form in the +2 and +4 oxidation states. Because einsteinium is radioactive, these compounds haven't been studied in great detail.

<span class="mw-page-title-main">Terbium compounds</span> Chemical compounds with at least one terbium atom

Terbium compounds are compounds formed by the lanthanide metal terbium (Tb). Terbium generally exhibits the +3 oxidation state in these compounds, such as in TbCl3, Tb(NO3)3 and Tb(CH3COO)3. Compounds with terbium in the +4 oxidation state are also known, such as TbO2 and BaTbF6. Terbium can also form compounds in the 0, +1 and +2 oxidation states.

Cobalt compounds are chemical compounds formed by cobalt with other elements. In the compound, the most stable oxidation state of cobalt is the +2 oxidation state, and in the presence of specific ligands, there are also stable compounds with +3 valence. In addition, there are cobalt compounds in high oxidation states +4, +5 and low oxidation states -1, 0, +1.

<span class="mw-page-title-main">Copper compounds</span> Chemical compounds containing copper

Copper forms a rich variety of compounds, usually with oxidation states +1 and +2, which are often called cuprous and cupric, respectively. Copper compounds, whether organic complexes or organometallics, promote or catalyse numerous chemical and biological processes.

References

  1. 1 2 3 Greenwood and Earnshaw, pp. 1244–8
  2. ↑ Greenwood and Earnshaw, pp. 1240–2
  3. 1 2 Greenwood and Earnshaw, pp. 1238–9
  4. ↑ Nair, Vijay; Deepthi, Ani (2007). "Cerium(IV) Ammonium NitrateA Versatile Single-Electron Oxidant". Chemical Reviews. 107 (5): 1862–1891. doi:10.1021/cr068408n. PMID   17432919.
  5. ↑ Sridharan, Vellaisamy; Menéndez, J. Carlos (2010). "Cerium(IV) Ammonium Nitrate as a Catalyst in Organic Synthesis". Chemical Reviews. 110 (6): 3805–3849. doi:10.1021/cr100004p. PMID   20359233.
  6. ↑ Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN   0-8493-0486-5.
  7. ↑ Gupta, C. K. & Krishnamurthy, Nagaiyar (2004). Extractive metallurgy of rare earths. CRC Press. p. 30. ISBN   978-0-415-33340-5.
  8. ↑ Gschneidner K.A., ed. (2006). "Chapter 229: Applications of tetravalent cerium compounds". Handbook on the Physics and Chemistry of Rare Earths, Volume 36. The Netherlands: Elsevier. pp. 286–288. ISBN   978-0-444-52142-2.
  9. ↑ Greenwood and Earnshaw, pp. 1242–4
  10. ↑ Daniel L. Reger; Scott R. Goode; David Warren Ball (2 January 2009). Chemistry: Principles and Practice. Cengage Learning. p. 482. ISBN   978-0-534-42012-3 . Retrieved 23 March 2013.
  11. ↑ Sroor, Farid M.A.; Edelmann, Frank T. (2012). "Lanthanides: Tetravalent Inorganic". Encyclopedia of Inorganic and Bioinorganic Chemistry. doi:10.1002/9781119951438.eibc2033. ISBN   978-1-119-95143-8.
  12. ↑ McGill, Ian. "Rare Earth Elements". Ullmann's Encyclopedia of Industrial Chemistry . Vol. 31. Weinheim: Wiley-VCH. p. 190. doi:10.1002/14356007.a22_607.
  13. ↑ B. P. Belousov (1959). "Периодически действующая реакция и ее механизм" [Periodically acting reaction and its mechanism]. Сборник рефератов по радиационной медицине (in Russian). 147: 145.
  14. ↑ Greenwood and Earnshaw, pp. 1248–9
  15. ↑ Schelter, Eric J. (20 March 2013). "Cerium under the lens". Nature Chemistry. 5 (4): 348. Bibcode:2013NatCh...5..348S. doi: 10.1038/nchem.1602 . PMID   23511425.
  16. ↑ Mikhail N. Bochkarev (2004). "Molecular compounds of "new" divalent lanthanides". Coordination Chemistry Reviews. 248 (9–10): 835–851. doi:10.1016/j.ccr.2004.04.004.
  17. ↑ M. Cristina Cassani; Yurii K. Gun'ko; Peter B. Hitchcock; Alexander G. Hulkes; Alexei V. Khvostov; Michael F. Lappert; Andrey V. Protchenko (2002). "Aspects of non-classical organolanthanide chemistry". Journal of Organometallic Chemistry. 647 (1–2): 71–83. doi:10.1016/s0022-328x(01)01484-x.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.