Ferromagnetic exchange coupling in a spiro-fused dinuclear nickel(II) complex with an approximate D2d symmetry

Ferromagnetic exchange coupling was operative between nickel(II) spins in a dinuclear nickel(II) complex [{Ni(hfac)2}2(py4C)] with J/kB = +0.57(2) K (H = −2JS1 · S2), where hfac and py4C stand for 1,1,1,5,5,5-hexafluoropentane-2,4-dionate and tetrakis(2-pyridyl)methane, respectively. X-ray crystal structure analysis revealed an approximate D2d symmetry of the [Ni(py4C)Ni] core and accordingly the orthogonal arrangement between the two coordination basal planes. Mechanism of the ferromagnetic coupling was proposed on the basis of the orthogonal dσ-type magnetic orbitals, which was supported by DFT calculation.