title: Pentachloro(pyrazine)rhenate(IV) complex as precursor of heterobimetallic pyrazine-containing Re(IV)2M(II) (M = Ni, Cu) species: synthesis, crystal structures and magnetic properties.
abstract: Three novel Re(IV) mononuclear complexes of formulae NBu4[ReC15(pyz)] (1), NH2Me2[ReCl5(pyz)] (2) and NH4[ReCl5(pyz)].0.75H2O (3), (pyz being pyrazine; NBu4+ = tetra-n-butylammonium cation, NH2Me2+ = dimethylammonium cation and NH4+ = ammonium cation), were synthesized by ligand substitution reaction from [ReCl6]2- anion and pyrazine in N,N-dimethylformamide (DMF). In addition, two new heterobimetallic compounds, the salt namely [ReCl5(pyz)]2[Ni(cyclam)](4) (cyclam = 1,4,8,11-tetraazacyclotetradecane) and the heterotrinuclear [{ReCl5(mu-pyz)}2Cu(DMF)4] (5) complex, were prepared by using as precursor 1 and 3, respectively. Compounds 1-5 were characterized by single-crystal X-ray diffraction. 1-3 are made up of discrete [ReCl5(pyz)]- anions and NBu4 (1), NH2Me2+ (2) and NH4+ (3) cations. [ReCl5(pyz)]- unit interacts toward Ni(II) (4) and Cu(II) (5) metal ions through different modes. In 4 two [ReCl5(pyz)]- anions weakly interact with a [Ni(cyclam)]2+ cation through chloro atoms, while compound 5 is a heterotrinuclear pyrazine-bridged Re(IV)2Cu(II) complex made up of [ReCl5(pyz)]- anions and [Cu(DMF)4]2+ cations. The magnetic properties of 1-5 were investigated in the temperature range 1.9-300 K. The magnetic behaviour of 1 is that of a magnetically diluted Re(IV) complex with a large value of zero-field splitting of the ground state (/2D/ is ca. 18.8(1) cm(-1)), whereas those of 2 and 3 are typical of antiferromagnetically coupled systems exhibiting susceptibility maxima at 10 (2) and 12 K (3). Compound 4 shows antiferromagnetic interactions between Re(IV) metal ions, Ni(II) being diamagnetic (because of its square-planar geometry), while 5 exhibits a ferromagnetic coupling between Re(IV) and Cu(II) metal ions across the pyrazine bridges with a J(ReCu), value of +11.8(1) cm(-1).
authors.affiliation: Departamento de Química Inorgánica/Instituto de Ciencia Molecular, Facultad de Química de la Universidad de Valencia, Dr. Moliner 50, 46100, Burjassot, Valencia, Spain. lillo@uv.es
authors.forename: José
authors.initials: J
authors.lastname: Martínez-Lillo
authors.forename: Donatella
authors.initials: D
authors.lastname: Armentano
authors.forename: Nadia
authors.initials: N
authors.lastname: Marino
authors.forename: Livia
authors.initials: L
authors.lastname: Arizaga
authors.forename: Raúl
authors.initials: R
authors.lastname: Chiozzone
authors.forename: Ricardo
authors.initials: R
authors.lastname: González
authors.forename: Carlos
authors.initials: C
authors.lastname: Kremer
authors.forename: Joan
authors.initials: J
authors.lastname: Cano
authors.forename: Juan
authors.initials: J
authors.lastname: Faus