Di- and trivalent Bis(stannolediides) of Dysprosium and Terbium: A novel class of High-Performance Single Molecule Magnets

Two isostructural homoleptic η5-stannole complexes of trivalent lanthanides [Ln(η5-L$^{Sn}$)$_2$K(thf)$_4$], where Ln = Tb, Dy and L$^{Sn}$ = [1,4-bis-(tert-butyl-dimethylsilyl)-2,3-bis-phenyl-stannolediide], have been synthesized via salt metathesis of the ligand’s bis-potassium salt with anhydrous lanthanide iodide. The trivalent complex [Tb(η$_5$-L$^{Sn}$)]– was obtained by subsequent removal of the potassium cation. In contrast, the same reaction of [Dy(η5-L$^{Sn}$)]–led to the divalent complex [Dy(η$_5$-L$^{Sn}$)]$^{2-}$ in a unprecedent reaction pathway. These four complexes can be considered as the very first examples of homoleptic compounds with heavy atom group 14 heterocyclic ligands. Magnetic investigations reveal single molecule magnet behavior for all investigated complexes. The trivalent Dy complex is found to be a remarkable SMM with an energy barrier of 1375 K and a blocking temperature of 54 K, while the [Dy(η$_5$-L$^{Sn}$)]$^{2-}$ complex is a rare example of a divalent Dy complex showing magnetic anisotropy. These results prove the potential of the homoleptic bis(stannolediides) of dysprosium and terbium as novel class of promising magnetic complexes within future molecular quantum information concepts.