Compounds of californium

Californium(III) bromide

Few compounds of californium have been made and studied.[1] The only californium ion that is stable in aqueous solutions is the californium(III) cation.[2] The other two oxidation states are IV (strong oxidizing agents) and II (strong reducing agents).[3] The element forms a water-soluble chloride, nitrate, perchlorate, and sulfate and is precipitated as a fluoride, oxalate or hydroxide.[4] If problems of availability of the element could be overcome, then CfBr2 and CfI2 would likely be stable.[5]

The +3 oxidation state is represented by californium(III) oxide (yellow-green, Cf2O3), californium(III) fluoride (bright green, CfF3) and californium(III) iodide (lemon yellow, CfI3).[3] Other +3 oxidation states include the sulfide and metallocene.[6] Californium(IV) oxide (black brown, CfO2), californium(IV) fluoride (green, CfF4) represent the IV oxidation state. The II state is represented by californium(II) bromide (yellow, CfBr2) and californium(II) iodide (dark violet, CfI2).[3]


Californium(IV) oxide (CfO2) is a black-brown solid that has a cubic crystal structure with a lattice parameter, the distance between unit cells in the crystal, of 531.0 ± 0.2 pm.[7] Crystals of californium(III) oxide normally have a body-centered cubic symmetry. They convert to a monoclinic form upon heating to about 1400 °C and melt at 1750 °C.[7]

Californium(III) chloride (CfCl3) is an emerald green compound with a hexagonal structure that can be prepared by reacting Cf2O3 with hydrochloric acid at 500 °C.[8] CfCl3 is then used as a feeder stock to form the yellow-orange triiodide CfI3, which in turn can be reduced to the lavender-violet diiodide CfI2.[9]

Californium(III) fluoride (CfF3) is a yellow-green solid with a crystal symmetry that gradually changes from orthorhombic to trigonal when heated above room temperature.[10] Californium(IV) fluoride (CfF4) is a bright green solid with a monoclinic crystal structure.[11]

Californium(II) iodide (CfI2) is a deep purple solid with a stable rhombohedral structure at room temperature and an unstable hexagonal structure. Californium(III) iodide (CfI3) is a lemon-yellow solid that has a rhombohedral structure and sublimes at ~800 °C.[12]

Californium(III) oxyfluoride (CfOF) is prepared by hydrolysis of californium(III) fluoride (CfF3) at high temperature.[13] Californium(III) oxychloride (CfOCl) is prepared by hydrolysis of the hydrate of californium(III) chloride at 280–320 °C.[14]

Heating the sulfate in air at about 1200 °C and then reducing with hydrogen at 500 °C produces the sesquioxide (Cf2O3).[8] The hydroxide Cf(OH)3 and the trifluoride CfF3 are slightly soluble.[8]

Californium(III) oxychloride (CfOCl) was the first californium compound to be discovered.[15]

Californium(III) polyborate is unusual in that californium is covalently bound to the borate.[16]

Californium is the second-heaviest element for which an organometallic compound is known. Cp3Cf (Cp = C5H5) was prepared from reaction of Cp2Be and CfCl3 on microgram scale and characterized by X-ray crystallography.[17]

See also


  1. Krebs, Robert (2006). The History and Use of our Earth's Chemical Elements: A Reference Guide. Westport, Connecticut: Greenwood Publishing Group. pp. 327–328. ISBN 978-0-313-33438-2.
  2. CRC 2006, p. 4-8.
  3. 1 2 3 Jakubke 1994, p. 166.
  4. Seaborg 2004.
  5. Greenwood 1997, p. 1272.
  6. Cotton 1999, p. 1163.
  7. 1 2 Baybarz, R. D.; Haire, R. G.; Fahey, J. A (1972). "On the Californium Oxide System". Inorganic and Nuclear Chemistry. 34 (2): 557–565. doi:10.1016/0022-1902(72)80435-4.
  8. 1 2 3 Cunningham 1968, p. 105.
  9. Cotton, Simon (2006). Lanthanide and Actinide Chemistry. West Sussex, England: John Wiley & Sons. p. 168. ISBN 978-0-470-01006-8.
  10. Stevenson, J. N; Peterson, J. R. (1973). "The Trigonal and Orthorhombic Crystal Structures of CfF3 and their Temperature Relationship". Inorganic and Nuclear Chemistry. 35 (10): 3481–3486. doi:10.1016/0022-1902(73)80356-2.
  11. Chang, C-T. P.; Haire, R. G.; Nave, S. E. (1990). "Magnetic Susceptibility of Californium Fluorides". Physical Review B. 41 (13): 9045–9048. Bibcode:1990PhRvB..41.9045C. doi:10.1103/PhysRevB.41.9045.
  12. Macintyre, J. E.; Daniel, F. M.; Stirling, V. M. (1992). Dictionary of inorganic compounds. London: Chapman and Hall, CRC Press. p. 2826. ISBN 978-0-412-30120-9.
  13. Peterson, J. R.; Burns, John H. (1968). "Preparation and Crystal Structure of Californium Oxyfluoride, CfOF". Inorganic and Nuclear Chemistry. 30 (11): 2955–2958. doi:10.1016/0022-1902(68)80155-1.
  14. Copeland, J. C.; Cunningham, B. B. (1969). "Crystallography of the Compounds of Californium. II. Crystal Structure and Lattice Parameters of Californium Oxychloride and Californium Sesquioxide". Inorganic and Nuclear Chemistry. 31 (3): 733–740. doi:10.1016/0022-1902(69)80020-5.
  15. Seaborg, Glenn T. (1963). Man-Made Transuranium Elements. Prentice-Hall.
  16. "Unusual structure, bonding, and properties may provide a new possibility for a californium borate". 1 June 2015. Retrieved 29 July 2015.
  17. Laubereau, Peter G.; Burns, John H. (1970). "Microchemical preparation of tricyclopentadienyl compounds of berkelium, californium, and some lanthanide elements". Inorganic Chemistry. 9 (5): 1091–1095. doi:10.1021/ic50087a018.


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