Ligand substitution in hexahalorhenate(IV) complexes: Synthesis, crystal structures and magnetic properties of NBu4[ReX5(DMF)] (X = Cl and Br)

The preparation, crystal structures, and magnetic properties of two rhenium(IV) mononuclear compounds of formula NBu4[ReX5(DMF)] View the MathML source(NBu4+=tetrabutylammonium cation and DMF=N,N-dimethylformamide) with X = Cl (1) and Br (2) are reported. 1 and 2 are isostructural complexes which crystallize in the monoclinic system with the space group P21/n. The rhenium atom is six-coordinated with five X atoms and a DMF molecule forming a somewhat distorted octahedral surrounding [values of Re–X varying in the ranges 2.317(1)–2.358(1) (1) and 2.495(1)–2.518(1) Å (2)]. Magnetic susceptibility measurements on samples of 1 and 2 in the temperature range 1.9–300 K are interpreted in terms of magnetically isolated spin quartets with large values of the zero-field-splitting (|2D| is ca. 20.2 and 39.2 cm−1 for 1 and 2, respectively).