Jahn Teller distortion and magnetic moments.
Planar complexes may be affected by this effect- not orthogonal complexes .  ref-(2017)
https://aip.scitation.org/doi/pdf/10.1063/1.4974805


  
    "The most striking result is that the planar copper(II) (3d9
    ) and nickel(II) (3d8
    )
    chelation afforded very strong ferromagnetic coupling often with 2J ≥ 300 K, owing to the orthogonal orbital
    arrangement between metal ion 3dx2-y2 and oxygen 2pz orbitals. Such a structure-magnetism relationship has
    recently been extended to coordination to rare earth metal ions."