A series of approximately trigonal planar heteroleptic Ln 3+ bis(silyl)amide complexes containing either TEMPO • radicals or TEMPO -anions have been synthesized and analyzed. The ideal equatorial coordination geometry of 2-Ln greatly stabilizes pure, magnetic ground states with prolate electron density in 2-Yb (>1000 cm -1 ) and 2-Tm (>390 cm -1 ). Stabilization of the ground state is reduced as the charge of the anionic coordination sphere decreases Tm, with exchange states split by ~0.32 cm -1 for 4-Yb. This work has shown that SMM behavior is not guaranteed even when approaching the limit of maximizing CF splitting in a Yb 3+ complex. We have highlighted other factors like the experimentally validated transverse g-values, which must also be controlled in the pursuit of Yb 3+ zero-field SMMs.