Which configuration is favored for d8 metals in a square planar geometry?

For d8 transition metal complexes, the square planar geometry is typically associated with low-spin configurations. This preference is primarily due to the specific arrangement and splitting of the d orbitals in square planar coordination.

In a square planar field, the d orbitals are split into distinct energy levels, where the dz2 orbital remains relatively high in energy, while the dx2-y2 and other orbitals fill at lower energies. The result of this splitting is that for d8 metals, the electrons prefer to pair up in the lower-energy orbitals instead of occupying higher energy orbitals alone.

Because of this stabilization of paired electrons and the energy considerations associated with filling the lower-energy orbitals first, low-spin configurations become the favored state. Consequently, in square planar complexes of d8 metals like nickel(II) and palladium(II), you will observe this paired electron scenario, leading to fewer unpaired electrons and resulting in properties typical of low-spin complexes, such as smaller magnetic moments.

Other configurations, such as high spin or intermediate spin, do not align with the established behavior of d8 metals in square planar geometry, as they would require the presence of unpaired electrons or a less favorable energy distribution among the d orbitals, which is