The resulting complex had what is known as square-planar geometry. This means that the nickel is in the center and the ligands are arranged around it at the four compass points, all in the same plane.

In solid-state materials, the unusual square-planar geometry of high-spin iron(II) in iron silicates has been attributed to constraint by the crystal lattice 5,6,7.

image: Changes to the natural tetrahedral structure of silicon (top left) in an unusual square planar geometry (bottom right). view more . Credit: Illustration: Ebner/Greb (Heidelberg) ...

Although the square-planar geometry is more common for the 2+ oxidation state of nickel, spectroscopic analysis confirmed this unusual electronic structure in this new complex.