Synthesis, crystal structure, and magnetic properties of a cyanide-bridged Fe^III₄Ni^II₂ hexa-nuclear complex based on tricyanideferrate(III)

A cyanide-bridged (Fe4Ni2II)-Ni-III hexa-nuclear complex [Fe4Ni2(Tp)(4)(CN)(12)(dpzpen)(2)] center dot 12H(2)O center dot 3CH(3)OH (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 (Fe2Ni2II)-Ni-III 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)) approximate to 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 degrees; J(2d): 0.206 2 nm, 163.1 degrees; J(1d): 0.198 7 nm, 161.6 degrees), 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.