Synthesis, crystal structure, and magnetic properties of a cyanide⁃bridged Fe^Ⅲ₄Ni^Ⅱ₂ hexa⁃nuclear complex based on tricyanideferrate(Ⅲ)

A cyanide - bridged Fe^Ⅲ₄Ni^Ⅱ₂ hexa - nuclear complex [Fe₄Ni₂(Tp)₄(CN)₁₂(dpzpen)₂]·12H₂O·3CH₃OH (1)(Tp=hydrotris(pyrazolyl)borate, dpzpen=2,9-di(pyrazo-1-yl)-1,10-phenanthroline) was prepared by the reaction of tricyanideferrate (Ⅲ) (Bu₄N) [Fe^Ⅲ (Tp) (CN)₃] with ligand dpzpen and Ni^Ⅱ salt. Structural analysis indicates that two [Fe^Ⅲ (Tp) (CN)₃] - units bridge two [Ni^Ⅱ (dpzpen)]²⁺ fragments forming an approximately rhombic Fe^Ⅲ₂Ni^Ⅱ₂ skeleton with another two [Fe^Ⅲ(Tp)(CN)₃]^- hanging outside the rhombus through cyanide bridges. Magnetic studies show that complex 1 exhibits ferromagnetic interaction between Fe^Ⅲ and Ni^Ⅱ through cyanide groups. More significantly, the magnetic - structural relationship of complex 1 was established by fitting the temperature dependence of magnetic susceptibility based on its structural model. The best-fitting parameters J_3d (15.73 cm^-1) > J_2d (3.53 cm^-1) ≈ J_1d (3.50 cm^-1) were in good agreement with the variation tendency of corresponding Ni—N bond lengths and Ni—N≡C angles (J_3d: 0.206 5 nm, 169.8°; J_2d: 0.206 2 nm, 163.1°; J_1d: 0.198 7 nm, 161.6°), indicating a shorter Ni—N bond length and a larger Ni—N≡C angle in favor of ferromagnetic interaction for cyanide - bridged Fe^Ⅲ - Ni^Ⅱ system. CCDC: 2239885.