[Fe(Phen)(CN)4]-:: A versatile building block for the design of heterometallic systems.: Crystal structures and magnetic properties of PPh4[Fe(Phen)(CN)4]•2H2O and [{Fe(Phen)(CN)4}2M(H2O)2]•4H2O [Phen=1,10-phenanthroline; M = Mn(II) and Zn(II)]

The mononuclear PPh4[Fe(phen)(CN)(4)]. 2H(2)O (1) complex and the cyanide-bridged bimetallic [{Fe(phen)(CN)(4)}(2)M-(H2O)(2)]. 4H(2)O compounds [M = Mn(II) (2) and Zn(II) (3); phen = 1,10-phenanthroline; PPh4 = tetraphenylphosphonium cation] have been synthesized and structurally and magnetically characterized. Complex 1 crystallizes in the monoclinic system, space group P2(1)/c, with a = 9.364(4) Angstrom, b 27.472(5) Angstrom, c = 14.301(3) Angstrom, beta = 97.68(2)degrees, and Z = 4. Complexes 2 and 3 are isostructural and they crystallize in the monoclinic system, space group P2(1)/n, with a = 7.5292(4) Angstrom, b = 15.6000(10) Angstrom, c 15.4081(9) Angstrom, beta = 93.552(2)degrees, and Z = 2 for 2 and a = 7.440(1) Angstrom, b = 15.569(3) Angstrom, c = 15.344(6) Angstrom, beta = 93.63(2)degrees, and Z = 2 for 3. The structure of complex 1 is made up of mononuclear [Fe(phen)(CN)(4)](-) anions, tetraphenyphosphonium cations, and water molecules of crystallization, The iron(III) is hexacoordinate with two nitrogen atoms of a chelating phen (2.018(6) and 2.021(6) Angstrom for Fe-N) and four carbon atoms of four terminal cyanide groups (Fe-C bond lengths varying in the range 1.906(8)-1.95(1) Angstrom) building a distorted octahedron around the metal atom. The structure of complexes 2 and 3 consists of neutral double zigzag chains of formula [{Fe(phen)(CN)(4)}(2)M(H2O)(2)] and crystallization water molecules. The [Fe(phen)(CN)(4)](-) entity of 1 is present in 2 and 3 acting as a bridging ligand toward M(H2O)(2) units [M = Mn(II) (2) and Zn(II) (3)] through two cyanide groups in cis positions, the other two cyanide remaining terminal. Two water molecules in trans positions and four cyanide-nitrogen atoms from four [Fe(phen)(CN)(4)](-) units build a distorted octahedral surrounding Mn(II) (2) and Zn(II) (3). The M-O bond lengths are 2.185(3) (2) and 2.105(3) Angstrom (3), whereas the M-N bond distances vary in the ranges 2.210(3)-2.258(3) Angstrom (2) and 2.112(3)-2.186(3) Angstrom (3). The structure of the [Fe(phen)(CN)(4)](-) complex ligand in 2 and 3 is as in 1. The shorter intrachain Fe-M distances through bridging cyano are 5.245(5) and 5.208(5) Angstrom in 2 and 5.187(1) and 5.132(1) Angstrom in 3. The magnetic properties of 1-3 have been investigated in the temperature range 2.0-300 K. Complex 1 is a low-spin iron(III) complex with an appreciable orbital contribution. The magnetic properties of 3 correspond to the sum of two magnetically isolated spin triplets, the magnetic coupling between the low-spin iron(III) centers through the -CN-Zn-NC- bridging skeleton (iron-iron separation larger than 10.2 Angstrom) being negligible. More interestingly, 2 exhibits one-dimensional ferrimagnetic behavior due to the noncompensation of the local interacting spins (S-Mn = 5/2 and S-Fe = 1/2) which interact antiferromagnetically through bridging cyano groups. A comparison between the magnetic properties of the isostructural compounds 2 and 3 allow us to check the antiferromagnetic coupling in 2.