The tetrabromonickelate anion contains a doubly-charged nickel atom (Ni2+) surrounded by four bromide ions in a tetrahedral arrangement. The formula is [NiBr4]2−.
The anion combines with cations to form a series of salts called tetrabromonickelates. Strongly-coordinating solvents will displace one or more of the bromido ligands from the complex.[1] Solvents that can dissolve tetrabromonickelate include acetone, acetonitrile, methyl ethyl ketone, and nitromethane.[2]
In the visible absorption spectrum there is a strong absorption band termed ν3 near 710 nm which is caused by an electronic transition from 3T1(F) → 3T1(P). Another strong absorption in the near infrared called ν2 near 770 nm is due to the 3T1(F) → 3A2(F) transition.[2]