[ReF 6 ] 2− : A Robust Module for the Design of Molecule‐Based Magnetic Materials

A facile synthesis of the [ReF 6 ] 2− ion and its use as a building block to synthesize magnetic systems are reported. Using dc and ac magnetic susceptibility measurements, INS and EPR spectroscopies, the magnetic properties of the isolated [ReF 6 ] 2− unit in (PPh 4 ) 2 [ReF 6 ]⋅2 H 2 O ( 1 ) have been fully studied including the slow relaxation of the magnetization observed below ca. 4 K. This slow dynamic is preserved for the one‐dimensional coordination polymer [Zn(viz) 4 (ReF 6 )] ∞ ( 2 , viz=1‐vinylimidazole), demonstrating the irrelevance of low symmetry for such magnetization dynamics in systems with easy‐plane‐type anisotropy. The ability of fluoride to mediate significant exchange interactions is exemplified by the isostructural [Ni(viz) 4 (ReF 6 )] ∞ ( 3 ) analogue in which the ferromagnetic Ni II –Re IV interaction (+10.8 cm −1 ) dwarfs the coupling present in related cyanide‐bridged systems. These results reveal [ReF 6 ] 2− to be an unique new module for the design of molecule‐based magnetic materials.