Syntheses, structures, and magnetic properties of a novel mer-[(bbp)FeIII(CN)3]2- building block (bbp: bis(2-benzimidazolyl)pyridine dianion) and its related heterobimetallic Fe(III)-Ni(II) complexes
Résumé
A new symmetrical tricyanide building block mer-[Fe(bbp)(CN)(3)](2-) [1; bbp = bis(2-benzimidazolyl)pyridine dianion] has been prepared and structurally and magnetically characterized. It forms a new low-spin meridionally capped {Fe(III)L(CN)(3)} fragment with the tridentate bbp ligand. The reaction of 1 with Ni(II) salts in the presence of various ancillary ligands affords several new cyanido-bridged complexes: a trinuclear complex {[Ni(ntb)(MeOH)](2)[Fe(bbp)(CN)(3)][ClO(4)](2)}*2MeOH (2), a tetranuclear compound {[Ni(tren)](2)[Fe(bbp)(CN)(3)](2)}*7MeOH (3), and a one-dimensional heterobimetallic system: {[Ni(dpd)(2)](2)[Fe(bbp)(CN)(3)](2)}*9MeOH*3H(2)O (4) [ntb = tris(2-benzimidazolylmethyl)amine, tren = tris(2-aminoethyl)amine, and dpd = 2,2-dimethyl-1,3-propanediamine]. The structural data shows that 2 is a linear complex in which a central Fe(III) ion links two adjacent Ni(II) ions via axial cyanides, while 3 is a molecular square that contains cyanido-bridged Ni(II) and Fe(III) ions at alternate corners. Complex 4 is a one-dimensional system that is composed of alternating cyanido-bridged Ni(II) and Fe(III) centers. Compounds 2-4 display extensive hydrogen bonding and moderately strong π-π stacking interactions in the solid state. Magnetic studies show that ferromagnetic exchange is operative within the Fe(III)(LS)(μ-CN)Ni(II) units of 2-4.