title: Synthesis, Crystal Structure, and Magnetic Properties of Tetraphenylarsonium Tetrachloro(oxalato)rhenate(IV) and Bis(2,2'-bipyridine)tetrachloro(&mgr;-oxalato)copper(II)rhenium(IV).
abstract: Two new rhenium(IV) compounds of formula (AsPh(4))(2)[ReCl(4)(ox)] (1) and [ReCl(4)(&mgr;-ox)Cu(bipy)(2)] (2) (AsPh(4) = tetraphenylarsonium cation, ox = oxalate anion, and bipy = 2,2'-bipyridine) have been synthesized and their crystal structures determined by single-crystal X-ray diffraction. 1 and 2 crystallize in the monoclinic system, space groups P2(1)/c and P2(1)/n, respectively, with a = 22.250(5) Å, b = 11.245(3) Å, c = 19.089(4) Å, beta = 96.59(2) degrees, and Z = 4 for 1 and a = 9.421(2) Å, b = 16.909(4) Å, c = 16.179(4) Å, beta = 93.97(2) degrees, and Z = 4 for 2. The structure of 1 is made up of [ReCl(4)(ox)](2)(-) anions and AsPh(4)(+) cations held united by electrostatic forces. Rhenium(IV) is hexacoordinate, with two oxygens of a chelating ox and four chlorine atoms building a distorted octahedron around the metal atom. There is no contact between the [ReCl(4)(ox)](2)(-) anions, the shortest Re.Re and Cl.Cl distances being 10.345 and 7.209 Å, respectively. This anionic complex is coordinated to a [Cu(bipy)(2)](2+) cation in 2, through one oxalate-oxygen, giving a neutral heterometallic dinuclear unit. The Cu(II) ion shows a very distorted five-coordinated geometry, four bipy-nitrogens occuping the equatorial positions and the oxygen atom the apical one. The basal plane geometry is distorted toward the tetrahedron, the dihedral angle between the mean planes of the two bipy ligands is 37.6(2) degrees. These [ReCl(4)(&mgr;-ox)Cu(bipy)(2)] units are arranged in such a way that a chlorine atom of one of them points toward the copper atom of the neighboring one, forming helicoid chains. The intrachain Re.Cu distances through chloro and oxalato bridges are 4.658 and 4.798 Å, respectively. The magnetic behavior of 1 and 2 has been investigated over the temperature range 1.8-300 K. 1 is a magnetically diluted Re(IV) complex, the great value of zero-field splitting of the ground level (D = 60 cm(-)(1)) accounting for the variation of chi(M)T with T in the low-temperature range. 2 behaves as a ferrimagnetic chain, with weak antiferromagnetic interactions between Re(IV) and Cu(II) through oxalato and single chloro bridges.
authors.affiliation: Cátedra de Química Inorgánica, Facultad de Química de la Universidad de la República, Montevideo, Uruguay, Dipartimento di Chimica, Università degli Studi della Calabria, 87030 Arcavacata di Rende, Cosenza, Italy, and Departamento de Química Inorgánica, Facultad de Química de la Universidad de Valencia, Dr. Moliner 50, 46100 Burjassot, Valencia, Spain.
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: Giovanni
authors.initials: G
authors.lastname: De Munno
authors.forename: Joan
authors.initials: J
authors.lastname: Cano
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