Self-Assembled One- and Two-Dimensional Networks Based on NH₂Me₂[ReX₅(DMF)] (X = Cl and Br) Species: Polymorphism and Supramolecular Isomerism in Re(IV) Compounds

Three mononuclear rhenium(IV) compounds of general formula NH2Me2[ReX5(DMF)] [NH2Me2+ = dimethylammonium cation, DMF = N,N-dimethylformamide, and X = Cl (1 and 2) and Br (3)] have been prepared and characterized. In all three cases, the rhenium atom is six-coordinated by five chloro (1 and 2) or bromo (3) atoms and one oxygen atom from a DMF molecule (1−3) building a somewhat distorted octahedral surrounding. Short ReIV−X···X−ReIV contacts and H-bonds occur in the crystal lattice generating novel supramolecular Re(IV) architectures. 1 and 2 are polymorphs and supramolecular isomers that exhibit supramolecular ladder-like (1) and rectangular two-dimensional grids (2), the different intermolecular X···X contacts playing a structure-determining role. Noteworthy, the formation of 1 and 2 is selective and dependent on the crystallization conditions. Although compound 3 is isolated using the same crystallization conditions as 2, their crystal packing is different. The investigation of the magnetic behavior of 1−3 in the temperature range 1.9−250 K showed the occurrence of maxima of the magnetic susceptibility at 10.5 (1), 12.0 (2), and 17.0 K (3), which are the signature of significant intermolecular antiferromagnetic interactions. The short ReIV−X···X−ReIV contacts provide the exchange pathway for the overall antiferromagnetic behavior observed in 1−3. The magnetostructural results of 1−3 are compared with those of the related compounds NBu4[ReX5(DMF)] [NBu4+ = tetra-n-butylammonium cation with X = Cl (4) and Br (5)] which were reported elsewhere.