The origin of 60 K magnetic hysteresis in the dysprosocenium complex [Dy(Cp-ttt)(2)][B(C6F5)(4)] (Cp-ttt = (C5H2Bu3)-Bu-t-1,2,4, 1-Dy) remains mysterious, thus we envisaged that analysis of a series of [Ln(Cp-ttt)(2)](+) (Ln = lanthanide) cations could shed light on these properties. Herein we report the synthesis and physical characterization of a family of isolated [Ln(Cp-ttt)(2)](+) cations (1-Ln; Ln = Gd, Ho, Er, Tm, Yb, Lu), synthesized by halide abstraction of [Ln(Cp-ttt)(2)(Cl)] (2-Ln; Ln = Gd, Ho, Er, Tm, Yb, Lu). Complexes within the two families 1-Ln and 2-Ln are isostructural and display pseudo-linear and pseudo-trigonal crystal fields, respectively. This results in archetypal electronic structures, determined with CASSCF-SO calculations and confirmed with SQUID magnetometry and EPR spectroscopy, showing magnetic anisotropy depending on the choice of Ln ion. Study of their magnetic relaxation dynamics exhibits an anomalously low Raman exponent similar to 1-Dy, both being distinct from the larger and more regular Raman exponents for 2-Dy, 2-Er, and 2-Yb. This suggests that low Raman exponents arise from the unique spin-phonon coupling of isolated [Ln(Cpttt)2]+ cations. Crucially, this highlights a direct connection between ligand coordination modes and spin-phonon coupling, and therefore we propose that the exclusive presence of multihapto ligands in 1-Dy is the origin of its remarkable magnetic properties. Controlling the spin-phonon coupling through ligand design thus appears vital for realizing the next generation of high-temperature single-molecule magnets.