The hexahalorhenate(IV) salts of formula [Fe(C5H5)2]2[ReX6], with X = Cl (1), Br (2), and I (3), and [Fe(C5Me5)2]2[ReX6], with X = Cl (4), Br (5), and I (6) ([Fe(C5Me5)2]+ = decamethylferrocenium cation), have been synthesized and the structures of 1, 2, and 4 determined by single-crystal X-ray diffraction. 1, 2, and 4 crystallize in the orthorhombic system, space groups Pbca (1 and 2) and Ibam (4), with a = 14.099(2) A, b = 16.125(2) A, and c = 22.133(15) A, for 1, a = 14.317(3) A, b = 16.848(3) A, and c = 22.099(2) A for 2, and a = 15.8583(5) A, b = 15.9368(5) A, and c = 16.9816(6) A for 4. The three structures are made up of discrete [ReX6]2- anions and ferrocenium cations held together by electrostatic forces. There are anion-anion contacts in 1 and 2 but only through one direction. The [ReX6]2- octahedra are arranged along the y axis forming chains of Re and X atoms, -Re-X...X-Re-X...X-Re-, where the intermolecular X...X distances are shorter than the van der Waals distances. A somewhat greater separation between the anions occurs in 4. The magnetic properties of 1-6 were investigated in the temperature range 2.0-300 K. 1, 2, 4, and 5 exhibit an antiferromagnetic coupling between the anions, whereas a ferromagnetic coupling between anions and cations is the dominant interaction in 3. 6 behaves as a magnetically isolated compound, its susceptibility being the simple addition of the independent contributions of the uncoupled paramagnetic cations and anions.

The preparation, crystal structures and magnetic properties of four different manganese() compounds of formula [Mn(bipym)Cl 2 ] n ؒ2nH 2 O (1), [Mn 2 (dpp) 3) and [Mn(dpp)(dca) 2 ] n (4) [bipym = 2,2Ј-bipyrimidine, dpp = 2,3-bis(2-pyridyl)pyrazine and dca = dicyanamide anion] are reported. Compounds 1 and 3 are uniform chains of six-coordinated manganese() ions bridged by bis(bidentate) bipym (1) and dpp (3) ligands with two chloride groups (1) and two water molecules (3) in cis position. The electroneutrality in 3 is achieved by uncoordinated perchlorate anions. The manganese atom in 1 and 3 exhibits a distorted octahedral environment mainly due to the short bite angle at the bis(chelating) bipym [70.9(1)Њ] and dpp [72.6(2)Њ] ligands. The intrachain Mn ؒ ؒ ؒ Mn separations are 6.164(1) Å in 1 and 7.289(2) Å in 3. Complex 2 is binuclear with a pair of chlorine atoms bridging the manganese atoms in a central Mn 2 Cl 2 plane, the intramolecular Mn ؒ ؒ ؒ Mn separation being 3.805(2) Å. Each manganese atom in 2 is six-coordinated with two nitrogen atoms from a bidentate dpp, a water molecule and three chlorine atoms (one terminal and two bridging) building a distorted octahedral environment. Compound 4 is a rhombic layered compound where the manganese atoms of each sheet are linked by single µ-1,5-dca bridges with Mn ؒ ؒ ؒ Mn separations of 6.909(1) and 7.674(1) Å. Each manganese atom in 4 is in a distorted octahedral environment, being coordinated to six nitrogen atoms, four from dca ligands and two from a bidentate dpp molecule. Magnetic susceptibility measurements for 1-4 in the temperature range 1.9-290 K show the occurrence of significant magnetic interactions between the local high spin manganese() ions which are antiferromagnetic across bridging bipym (J = Ϫ1.19 cm Ϫ1 , 1), dpp (J = Ϫ0.25 cm Ϫ1 , 3) and dca (J = Ϫ0.26 cm Ϫ1 , 4) and ferromagnetic through the double-µ-chloro bridge (J = ϩ0.11 cm Ϫ1 , 2).

The structural characterization of a series of complexes of formula [M(dca)2L]n, where dca = dicyanamide, L = 1,10-phenanthroline (phen) [1-4] and 2,9-dimethylphenanthroline (2,9-dmphen) [9-12], and M = Mn (1 and 9), Fe (2 and 10), Co (3 and 11), and Ni (4 and 12), has revealed the effect of the presence of the methyl substituents of L on the resulting network. The structure of [Mn(dca)2(phen)]n (1), which is identical to those of 2-4, together with the investigation of its magnetic properties in the temperature range of 77-300 K were reported elsewhere. The use of the 4,7-dimethylphenanthroline (4,7-dmphen) as the co-ligand yielded a series of compounds of formula [M(dca)2(4,7-dmphen)]n [M = Mn (5), Fe (6), Co (7), and Ni (8)], which are isostructural with 1-4. Compounds containing phen (1-4) and 4,7-dmphen (5-8) are made of two-dimensional grids of metal atoms, each metal atom being linked to three other metal centers through single (three metal atoms involved) and double (two metal atoms involved) dca bridges exhibiting the mu-1,5 coordination mode. The isostructural complexes [M(dca)2(2,9-dmphen)]n (9-12) also have a sheetlike structure, the metal atoms in each layer being linked by two single and one double mu-1,5-dca units, as in 1-8. However, the topology of the network in 9-12 is different from that in 1-8 because of the different arrangement of the two single mu-1,5 dca bridges: cis in 1-8 versus trans in 9-12. The magnetic study of compounds 1-12 in the temperature range of 1.9-290 K has revealed the occurrence of weak ferromagnetic (M = Ni) and antiferromagnetic interactions (M = Mn, Fe, and Co). The different magnetic behavior in 1-12 was analyzed in the light of their structures, and the values of the magnetic interactions were compared to those of related systems.