Fe(Phen)(CN)_4]~-: A Versatile Building Block for the Design of Heterometallic systems. Crystal Structures and Magnetic Properties of PPh_4[Fe(Phen)(CN)_4].2H_2O and [{Fe(Phen)(CN)_4}_2M(H_2O)_2].4H_2O [Phen=1,10-Phenanthroline; M=Mn(II) and Zn(II)

摘要

The mononuclear PP~[Fe(phen)(CN)4J.2H20 (I) complex and thecyanide-bridged bimetallic {{Fe(phen)(CN)4}2M- (H2O)2].4H2O compounds [M = Mn(II) (2) and Zn(II) (3); phen = 1.10-phenanthroline; PP~ = tetraphenylphos- phonium cation] have been synthesized and structurally and magnetically characterized. Complex I crystallizes in the monoclinic system, space group P21/c, with a = 9.364(4) A, b == 27.472(5) A, (; = 14.301(3) A, (3 = 97.68(2)0, and Z = 4. Complexes 2 and3 are isostructural and they crystallize in the monoclinic system, space group P21, with a = 7.5292(4) A, b = .15.6000(10) A, c = 15.4081(9) A, fJ = 93.552(2)0, and Z = 2 for 2 and a = 7.440(1) A, b = 15.569(3) A, c = 15.344(6) A, fJ = 93.63(2)0, and Z = 2 for 3. The structure of complex I is made up of mononuclear [Fe(phen)(CN)4]- anions,tetraphenyphosphonium cations, and water molecules of cl"ystallization. The iron(IlI) is hexacoordinate with two nitrogen atoms of a chelating phen (2.018(6) and 2.021(6) A 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 ) A) 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)4hM(H20)2J and crystallization water molecules. The [Fe(phen)(CN)4J- entity of I is present in 2 and 3 acting as a bridging ligand toward M(H2O)2 units [M = Mn(IIJ (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 fFe(phen)(CN)4J- 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) A (3), whereas the M-N bond distances vary in the ranges 2.210(3)-2.258(3) A (2) and 2.112(3)-2.186(3) A (3). The structure of the {Fe(phen)(CN)4]- complex ligand in 2 and 3 is as in I. The shorter intrachain Fe-M distances through bridging cyano are 5.245(5) and 5.208(5) A in 2 and 5.187(1) and 5.132(1) A in 3. The magnetic properties of 1- 3 have been investigated in the temperature range 2.0- 300 K. Complex I is a low-spin iron(IlI) complex with an appreciable orbital contribution. The magnetic properties of3 correspond to the sum of two magnetically isolated spin triplets, the magnetic coupling between the low-spin iron(IlI) centers through the -CN- Zn-NC- bridging skeleton (iron-iron separation larger than 10.2 A) being negligible. More interestingly, 2 exhibits one-dimensional ferrimagnetic behavior due to the noncompensation of the local interacting spins (SMn = 5/2 and SFe = 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.