Chromium compounds

The resulting bright blue solution created from dissolving chromium(II) chloride is stable at neutral pH.

Commercially available chromium(III) chloride hydrate is the dark green complex [CrCl2(H2O)4]Cl.

Closely related compounds are the pale green [CrCl(H2O)5]Cl2 and violet [Cr(H2O)6]Cl3.

This kind of reaction is also observed with solutions of chrome alum and other water-soluble chromium(III) salts.

A tetrahedral coordination of chromium(III) has been reported for the Cr-centered Keggin anion [α-CrW12O40]5–.

[6] However, despite several erroneous claims, chromium hexafluoride (as well as all higher hexahalides) remains unknown, as of 2020.

Both the chromate and dichromate anions are strong oxidizing reagents at low pH:[6] They are, however, only moderately oxidizing at high pH:[6] Chromium(VI) compounds in solution can be detected by adding an acidic hydrogen peroxide solution.

The unstable dark blue chromium(VI) peroxide (CrO5) is formed, which can be stabilized as an ether adduct CrO5·OR2.

Organic compounds containing Cr(IV) state such as chromium tetra t-butoxide are also known.

[15] Extremely bulky monodentate ligands stabilize this compound by shielding the quintuple bond from further reactions.