title: A novel series of rhenium-bipyrimidine complexes: synthesis, crystal structure and electrochemical properties.
abstract: Four novel rhenium complexes of formula [ReCl(4)(bpym)] (1), [ReBr(4)(bpym)] (2) PPh(4)[ReCl(4)(bpym)] (3) and NBu(4)[ReBr(4)(bpym)] (4) (bpym = 2,2'-bipyrimidine, PPh(4) = tetraphenylphosphonium cation and NBu(4) = tetrabutylammonium cation), have been synthesized and their crystal structures determined by single-crystal X-ray diffraction. The structures of 1 and 2 consist of [ReX(4)(bpym)] molecules held together by van der Waals forces. In both complexes the Re(iv) central atom is surrounded by four halide anions and two nitrogen atoms of a bpym bidentate ligand in a distorted octahedral environment. The structures of 3 and 4 consist of [ReX(4)(bpym)](-) anions and PPh(4)(+) () or NBu(4)(+) (4) cations. The coordination sphere of the Re(iii) metal ion is the same as in 1 and 2, respectively. However, whereas the Re-X bonds are longer the Re-N bonds are shorter than in 1 and 2. This fact reveals that the bpym ligand forms a stronger bond with Re(iii) than with Re(iv) resulting in a stabilisation of the lower oxidation state. [ReX(4)(bpym)] complexes are easily reduced, chemically and electrochemically, to the corresponding [ReX(4)(bpym)](-) anions. A voltammetric study shows that the electron transference is a reversible process characterized by formal redox potentials of +0.19 V (1) and +0.32 V (2) vs. NHE, in acetonitrile as solvent.
authors.affiliation: Cátedra de Química Inorgánica, Facultad de Química de la Universidad de la República, Avda. General Flores 2124, CC 1157, Montevideo, Uruguay. rchiozzo@fq.edu.uy
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: María Fernanda
authors.initials: MF
authors.lastname: Cerdá
authors.forename: Donatella
authors.initials: D
authors.lastname: Armentano
authors.forename: Giovanni
authors.initials: G
authors.lastname: De Munno
authors.forename: José
authors.initials: J
authors.lastname: Martínez-Lillo
authors.forename: Juan
authors.initials: J
authors.lastname: Faus