Influence of weakly coordinating anions binding to the hexa--butyl dysprosocenium cation.

Complexes containing isolated dysprosocenium cations, [Dy(Cp)][WCA] (Cp = substituted cyclopentadienyl, WCA = weakly coordinating anion), have recently emerged as leading examples of high-temperature single-molecule magnets (SMMs) due to a combination of the axial orientation and rigidity of the Cp rings. However, our understanding of the effects of transverse fields on the magnetic properties of [Dy(Cp)] cations is underdeveloped. Here we investigate the impact of equatorially-bound WCAs the synthesis of the Dy(III) bis-Cp complexes [Dy(Cp){AlCl[OC(CF)]-κ-}] (1) and [Dy(Cp){AlCl(CH)[OC(CF)]-κ-}] (2), and their characterisation by single crystal XRD, elemental analysis, ATR-IR and NMR spectroscopy, and calculations. Despite the similarity of the Dy coordination spheres in 1 and 2 we find that their effective energy barriers to reversal of magnetisation are vastly different ( = 886(17) cm and 559(18) cm, respectively) and they both show waist-restricted magnetic hysteresis at 2 K. Together, these data provide fresh insights into the sensitivity of the magnetic properties of [Dy(Cp)] cations to relatively weak equatorial interactions.