Dysprosiacarboranes as Organometallic Single-Molecule Magnets

The dicarbollide ion, nido-C2B9H112- is isoelectronic with cyclopentadienyl. Herein, we make dysprosiacarboranes, namely [(C2B9H11)(2)Ln(THF)(2)][Na(THF)(5)] (Ln=Dy, 1Dy) and [(THF)(3)(mu-H)(3)Li](2)[{eta(5)-C6H4(CH2)(2)C2B9H9}Dy{eta(2):eta(5)-C6H4(CH2)(2)C2B9H9}(2)Li] 3Dy and show that dicarbollide ligands impose strong magnetic axiality on the central Dy-III ion. The effective energy barrier (U-eff) for the loss of magnetization can be varied by the substitution pattern on the dicarbollide. This finding is demonstrated by comparing complexes of nido-C2B9H112- and nido-[o-xylylene-C2B9H9](2-), which show a U-eff of 430(5) K and 804(7) K, respectively. The blocking temperature defined by the open hysteresis temperature of 3Dy reaches 6.8 K. Moreover, the linear complex [Dy(C2B9H11)(2)](-) is predicted to have comparable properties with the linear [Dy(Cp-Me3)(2)](+) complex. As such, carboranyl ligands and their derivatives may provide a new type of organometallic ligand for high-performance single-molecule magnets.