The first Dy(III) complex containing no equatorially-bound ligands, [Dy )2][B(C6F5)4] (Cp ttt = C5H2 t Bu3-1,2,4), was reported in 2017; this SMM showed Ueff = 1223(15) cm -1 and TH = 60 K due to a combination of the axial ligand field and rigid aromatic Cp R (substituted cyclopentadienyl) rings hindering both Orbach and Raman relaxation. Related Ln SMMs with higher Ueff and TH values have since been achieved by decreasing Ln-L (L = ligand) distances and increasing L-Ln-L angles, and in an extension of this methodology the dinuclear complex [{Dy(C5 i Pr5)}2(μ-I)3] shows TH = 80 K and Ueff = 1631(25) cm -1 . Although smaller Cp R ligands allow shorter Ln-L distances (and thus could improve Ueff), they also permit less bulky [Dy )2] + cations to have more bent geometries, which leads to lower purity ±mJ states, faster Raman relaxation, and lower TH. Indeed, one of the smallest possible Cp R ligands Cp* = C5Me5 tends to form bent Dy(III) bis-Cp* complexes with equatorially-bound ligands, which have all showed low TH (< 12 K). Recently, we have been exploring the effect of weak equatorial binding of neutral halobenzenes to bent [Dy(Cp R )2] + cations, finding that they provide only minor disruption to the axiality if the complex geometry is preserved. We hypothesised that a fluorobenzene adduct of a mono-Cp* Dy(III) dication [Dy(Cp*)(FPh)n] 2+ would show reduced Ueff due to having only one Cp R ligand, but should have increased purity of low-lying ±mJ states vs. bent bis-Cp* cations and thus achieve a relatively high TH. Aside from magnetic properties, rare earth alkyl dications can be effective olefin polymerisation catalysts, but to the best of our knowledge the only previous structurally authenticated Ln(III) mono-cyclopentadienyl dication was seen in [Tm(Cp*)(NCMe)6][I]2 (Cp* = C5Me5). Here we report the six-legged piano stool Ln(III) complexes [Ln(Cp*)(FPh)6]