Wikipedia
Tetrabromonickelate
The tetrabromonickelate is an anion containing a doubly positive charged nickel atom (Ni) surrounded by four bromide ions in a tetrahedral shape. The formula is [NiBr].
The anion combines with cations to form a series of salts called tetrabromonickelates. Strongly coordinating or polar solvents will add solvent molecules displacing the bromine in the complex. Solvents that can dissolve tetrabromonickelate include acetone, acetonitrile, methyl ethyl ketone, and nitromethane.
In visible light there is a strong absorption band termed ν near 710 nm which is caused by an electronic transition from T(F) → T(P). Another strong absorption and is in the near infrared called ν near 770 nm due to T(F) → A(F).