Crystal structure and ferromagnetic behavior of a cis-Co(II) complex with nitronyl nitroxide

Bis(hexafluoroacetylacetonate)cobalt(II), Co(hfac)2, reacted with the nitronyl nitroxide radical 2-(4-methylphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, NITPhMe, to yield an octahedral adduct of formula Co(hfac)2(NITPhMe)2. The X-ray crystal structure shows that it crystallizes in the space group P1, with a = 9.837(3), b = 11.618(3), c = 20.502(4) Å, α = 81.22(2), β = 87.93(2), γ = 72.24(3)º, V = 2205(1) Å3, Z = 2. The mechanism of ferromagnetic exchange between cobalt(II) and the radical can be qualitatively understood in terms of a charge-transfer interaction (J being 25.7 cm-1, the Hamiltonian is written in the form H = -2J(SRad1·SCo + SCo·SRad2)).Key words: crystal structure, cobalt(II) complex, nitronyl nitroxide, magnetic property.