Ferromagnetic coupling between low- and high-spin iron(III) ions in the tetranuclear complex fac-{[Fe-III{HB(pz)(3)}(CN)(2)(mu-CN)](3)Fe-III(H2O)(3)}center dot 6H(2)O ([HB(pz)(3)](-) = hydrotris(1-pyrazolyl)borate)

摘要

The novel mononuclear PPh4-fac-[Fe-III{HB(pz)(3)}(CN)(3)].H2O (1) [PPh4+= tetraphenylphosphonium cation; (HB(pz)(3))(-) = hydrotris(1-pyrazolyl)borate] and tetranuclear fac-{[Fe-III{HB(pz)(3)}(CN)(2)(mu-CN)](3)Fe-III(H2O)(3)}.6H(2)O (2) have been prepared and characterized by X-ray diffraction analysis. Crystal data for compound 1: monoclinic, space group P2(1)/c, a = 9.575(3) Angstrom, b = 21.984(4) Angstrom, c = 16.863(3) Angstrom, beta = 100.34(2)degrees, U = 3486(1) Angstrom(3), Z = 4. Crystal data for compound 2: orthorhombic, space group Pnam, a = 14.084(3) Angstrom, b = 14.799(4) Angstrom, c = 25.725(5) Angstrom, U = 5362(2) Angstrom(3), Z = 4. Compound 1 is a low-spin iron(Ill) compound with three cyanide ligands in fac arrangement and a tridentate pyrazolylborate ligand building a distorted octahedral environment around the iron atom. Compound 2 is the first example of a molecular species containing three peripheral low-spin iron(Ill) ions linked to a central high-spin iron(III) cation by single cyanide bridges, the anion of 1 acting as a monodentate ligand in 2. Variable-temperature magnetic susceptibility measurements of 2 reveal the occurrence of a significant ferromagnetic coupling between the three peripheral low-spin iron(III) centers and the central high-spin iron(Ill) ion cations leading to a low-lying nonet spin state. [References: 26]