COMPLEJOS

ESTRUCTURA CRISTALINA

SINTESIS

BIBLIOGRAFIA NACIONAL QUIMICA

2013

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 Br⋯Br 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.

Dalton Transactions v. 42, no. 43, 2013. -- p. 15361-15371

Royal Society of Chemistry

2013

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Inglés

Artículo

DOI: 10.1039/C3DT51699G

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