Silvia Russi

Synthesis, crystal structure and magnetic properties of novel heterobimetallic malonate-bridged MIIReIV complexes (M = Mn, Fe, Co and Ni).

Five novel ReIV-MII bimetallic complexes of formula [ReCl4(mu-mal)M(dmphen)2].MeCN [M = Co (1), Fe (2) and Ni (3)], [ReCl4(mu-mal)Ni(dmphen)(MeCN)2(H2O)].(MeCN)0.5(H2O)0.5 (4), and [ReCl4(mu-mal)Mn(dmphen)(H2O)2].dmphen.MeCN.H2O (5) (mal = malonate dianion, dmphen = 2,9-dimethyl-1,10-phenanthroline) have been synthesized, and the structures of 1, 2, 4, and 5 determined by single-crystal X-ray diffraction. The structures of 1 and 2 consist of neutral [ReCl4(mu-mal)M(dmphen)2] dinuclear units where the metal ions are linked through a malonate ligand which adopts simultaneously the bidentate (at ReIV) and monodentate (at MII) coordination modes. The bridging carboxylate-malonate group in them exhibits the anti-syn conformation. The rhenium atom is six-coordinated with four chloro atoms and two carboxylate-oxygens from a bidentate malonate group in a distorted octahedral environment. The M atom is five-coordinated being surrounded by four nitrogen atoms of two bidentate dmphen ligands and one oxygen atom of the malonato ligand. There are also ReIV(mu-mal)NiII dinuclear units in 4 with the same type of bridge, but the nickel atom is six-coordinated with one bidentate dmphen, two molecules of acetonitrile and one water molecule as peripheral ligands. Compound 5 is a neutral chain compound with regular alternating rhenium(IV) and manganese(II) ions. The [ReCl4(mal)]2- units in each chain act as bismonodenate ligands through two carboxylate-oxygen atoms toward [Mn(dmphen)(H2O)2]2+ entities. Variable-temperature magnetic measurements of 1-5 in the temperature range 2.0-300 K show the occurrence of weak antiferromagnetic interactions which are rationalized on the basis of the structural knowledge and simple orbital considerations. Very noticeable is compound 5, a ferrimagnetic chain with regular alternating ReIV and MnII cations.

Mixed stacking and stoichiometry in a π-molecular complex between fluorene and 1,3,5-trinitrobenzene

The crystal structure of the title complex, fluorene-1,3,5-trinitrobenzene (1.5/2) (1.5C 13 H 10 .2C 6 H 3 N 3 O 6 ) has been determined at room temperature. The molecule crystallizes in a triclinic cell and in the P1 space group. One of the three fluorene molecules in the unit cell is located at a special position and adopts two different orientations that are related by an inversion center. Therefore, the asymmetric unit contains 1.5 fluorene molecules and two molecules of 1,3,5-trinitrobenzene. Acceptor and donor molecules are arranged in mixed stacks, one with 1:1 and the other with 2:1 trinitrobenzene:fluorene stoichiometries. This mixed arrangement and the composition of the asymmetric unit explains the global 4:3 stoichiometry. These two independent stacking directions are parallel to the c and a axes, respectively.

(1S,2S,5S,6S)-5,6-Dihydroxy-6-methylcyclohex-3-en-1,2-diyl diacetate

The title compound, C 11 H 16 O 6 , has been synthesized and isolated as the major product of the osmylation of (5S,6R)-5,6-diacetoxy-1-methyl-1,3-cyclohexadiene. The molecule crystallizes in the monoclinic space group P2 1 . The hexene ring exhibits a puckered distorted half-chair conformation, with all the chiral centres (C3, C4, C5 and C6) in the S configuration. One intramolecular and two intermolecular hydrogen bonds stabilize the molecule by the formation of infinite chains along b.