As shown in Table , the general ferromagnetic and antiferromagnetic σ components are nearly identical in magnitude to those of the copper complex. The antiferromagnetic δ component in the nickel complex is, as expected from magnetic orbital overlap considerations, essentially negligible. Introducing additional dynamic correlation via NEVPT2 increases the ferromagnetic and antiferromagnetic coupling contributions in the nickel complex, whereas for the copper complex only the antiferromagnetic contributions increased. While the rise in the δ antiferromagnetic contribution can be explained by dynamic charge polarization similar to the explanation for the σ contributions, spin polarization plays a significant role for the Table : Ferromagnetic and antiferromagnetic contributions (J AF,σ,δ/F ) for the equilibrium geometry of the nickel complex in (4,4) and (10,7) CASSCF and NEVPT2 calculations with the Ni -O -Ni angle scan method.