title: Magnetic properties and molecular structures of binuclear (2-pyrazinecarboxylate)-bridged complexes containing Re(IV) and M(II) (M = Co, Ni).
abstract: Three novel Re(iv) compounds, the mononuclear complex Bu(4)N[ReBr(5)(Hpyzc)] (1) and the heterobimetallic complexes [ReBr(5)(mu-pyzc)M(dmphen)(2)].2CH(3)CN [M = Co (2), Ni (3)] (Hpyzc = 2-pyrazinecarboxylic acid, dmphen = 2,9-dimethyl-1,10-phenanthroline), have been synthesized and their crystal structures determined by single-crystal X-ray diffraction. The structure of 1 consists of [ReBr(5)(Hpyzc)](-) complex anions and tetrabutylammonium cations, Bu(4)N(+). The Re(iv) is surrounded by five bromide anions and a N-donor Hpyzc monodentate ligand, in a distorted octahedral environment. The structures of 2 and 3 consist of dinuclear units [ReBr(5)(mu-pyzc)M(dmphen)(2)], with the metal ions linked by a pyzc bridge ligand, being bidentate toward M(II) and monodentate toward Re(IV). The environment of Re(IV) is the same as in 1, whereas M(II) is six-coordinate, being surrounded by four nitrogen atoms of two bidentate dmphen ligands and one oxygen atom and one nitrogen atom of the pyzc anion. The magnetic properties of 1-3 were investigated in the temperature range 2.0-300 K. 1 shows the expected magnetic behavior for a mononuclear Re(IV) complex with a weak intermolecular antiferromagnetic coupling at low temperatures. The bimetallic complexes exhibit an intramolecular ferromagnetic coupling between Re(IV) and the M(II) ion (Co, Ni).
authors.affiliation: Cáedra de Química Inorgánica, Departamento Estrella Campos, Facultad de Química de la Universidad de la República, Avda. General Flores 2124, CC 1157 Montevideo, Uruguay.
authors.forename: Alicia
authors.initials: A
authors.lastname: Cuevas
authors.forename: Carlos
authors.initials: C
authors.lastname: Kremer
authors.forename: Markus
authors.initials: M
authors.lastname: Hummert
authors.forename: Herbert
authors.initials: H
authors.lastname: Schumann
authors.forename: Francesc
authors.initials: F
authors.lastname: Lloret
authors.forename: Miguel
authors.initials: M
authors.lastname: Julve
authors.forename: Juan
authors.initials: J
authors.lastname: Faus