Californium compounds

Few compounds of californium have been made and studied. The only californium ion that is stable in aqueous solutions is the californium cation. The other two oxidation states are IV and II. The element forms a water-soluble chloride, nitrate, perchlorate, and sulfate and is precipitated as a fluoride, oxalate or hydroxide. If problems of availability of the element could be overcome, then CfBr₂ and CfI₂ would likely be stable.
The +3 oxidation state is represented by californium oxide, californium fluoride and californium iodide. Other +3 oxidation states include the sulfide and metallocene. Californium oxide, californium fluoride represent the IV oxidation state. The II state is represented by californium bromide and californium iodide.

Compounds

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. Crystals of californium 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.
Californium chloride is an emerald green compound with a hexagonal structure that can be prepared by reacting Cf₂O₃ with hydrochloric acid at 500 °C. 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.
Californium fluoride is a yellow-green solid with a crystal symmetry that gradually changes from orthorhombic to trigonal when heated above room temperature. Californium fluoride is a bright green solid with a monoclinic crystal structure.
Californium iodide is a deep purple solid with a stable rhombohedral structure at room temperature and an unstable hexagonal structure. Californium iodide is a lemon-yellow solid that has a rhombohedral structure and sublimes at ~800 °C.
Californium oxyfluoride is prepared by hydrolysis of californium fluoride at high temperature. Californium oxychloride is prepared by hydrolysis of the hydrate of californium chloride at 280–320 °C.
Heating the sulfate in air at about 1200 °C and then reducing with hydrogen at 500 °C produces the sesquioxide. The hydroxide Cf₃ and the trifluoride CfF₃ are slightly soluble.
Californium oxychloride was the first californium compound to be discovered.
Californium polyborate is unusual in that californium is covalently bound to the borate.
Triscalifornium presents itself as ruby red crystals. This cyclopentadienyl complex has been prepared by the reaction between Cp₂Be and CfCl₃ on a microgram scale and characterized by X-ray crystallography. Californium is the second-heaviest element for which an organometallic compound is known. A bent californium metallocene has also been isolated and characterized.