title: Synthesis, crystal structure and magnetic properties of the Re(II) complexes NBu4[Re(NO)Br4(L)] (L = pyridine and diazine type ligands).
abstract: Four novel Re(II) complexes of formula NBu4[Re(NO)Br4(L)] [NBu4(+) = tetra-n-butylammonium cation and L = pyridine (1), pyrazine (2), pyrimidine (3), pyridazine (4)] have been prepared by a substitution reaction involving NBu4[Re(NO)Br4(EtOH)] and L. Their crystal structures have been determined by single crystal X-ray diffraction. They are all mononuclear complexes whose structure is made up of [Re(NO)Br4L](-) anions and NBu4(+) cations. Each Re(II) ion is six-coordinate with four bromide ligands, a linear nitrosyl group and one monodentate nitrogen donor L building a tetragonally distorted octahedral surrounding. The Re-Br bond distances cover a narrow range [2.5048(8)-2.5333(5) Å] and they are longer than the Re-NO [1.688(15)-1.736(3) Å] and Re-N bonds [2.219(4)-2.234(3) Å]. The magnetic properties of 1-4 have been investigated in the temperature range 1.9-295 K. They behave like quasi magnetically isolated spin doublets with very weak antiferromagnetic interactions through intermolecular BrBr contacts. Their magnetic properties are discussed through a deep analysis of the influence of the ligand field, spin-orbit coupling, tetragonal distortion and covalence effects. The values of the temperature-independent paramagnetism for 1-4 are also substantiated and compared to those previously reported in related systems.
authors.affiliation: Cátedra de Química Inorgánica, Departamento Estrella Campos, Facultad de Química, Universidad de la República, Avda. General Flores 2124, Montevideo, Uruguay. ckremer@fq.edu.uy.
authors.forename: Mario
authors.initials: M
authors.lastname: Pacheco
authors.forename: Alicia
authors.initials: A
authors.lastname: Cuevas
authors.forename: Javier
authors.initials: J
authors.lastname: González-Platas
authors.forename: Ricardo
authors.initials: R
authors.lastname: Faccio
authors.forename: Francesc
authors.initials: F
authors.lastname: Lloret
authors.forename: Miguel
authors.initials: M
authors.lastname: Julve
authors.forename: Carlos
authors.initials: C
authors.lastname: Kremer