The best-performing single-molecule magnets (SMMs) have historically relied on pseudoaxial ligands delocalized across several coordinated atoms. This coordination environment has been found to elicit strong magnetic anisotropy, but lanthanide-based SMMs with low coordination numbers have remained synthetically elusive species. Here we report a cationic 4f complex bearing only two bis-silylamide ligands, Yb(III)[{N(SiMePh₂)₂}₂][Al{OC(CF₃)₃}₄], which exhibits slow relaxation of its magnetization. The combination of the bulky silylamide ligands and weakly coordinating [Al{OC(CF₃)₃}₄]⁻ anion provides a sterically hindered environment that suitably stabilizes the pseudotrigonal geometry necessary to elicit strong ground-state magnetic anisotropy. The resolution of the m_J states by luminescence spectroscopy is supported by ab initio calculations, which show a large ground-state splitting of approximately 1,850 cm⁻¹. These results provide a facile route to access a bis-silylamido Yb(III) complex, and further underline the desirability of axially coordinated ligands with well-localized charges for high-performing SMMs.

性能最佳的单分子磁体（SMM）历来依赖于跨多个配位原子离域的赝轴配体。人们发现这种配位环境会产生强磁各向异性，但具有低配位数的基于镧系元素的 SMM 仍然是合成上难以捉摸的物种。在这里，我们报道了仅带有两个双甲硅烷基酰胺配体的阳离子 4 f配合物 Yb(III)[{N(SiMePh ₂ ) ₂ } ₂ ][Al{OC(CF ₃ ) ₃ } ₄ ]，其表现出缓慢弛豫磁化。大体积的甲硅烷基酰胺配体和弱配位的[Al{OC(CF ₃ ) ₃ } ₄ ] ^-阴离子的组合提供了空间位阻环境，该环境适当地稳定了引发强基态磁各向异性所需的赝三角几何形状。从头算计算支持发光光谱对m _J态的分辨率，该计算显示大约 1,850 cm ^-1的大基态分裂。这些结果提供了一种获取双甲硅烷基酰胺 Yb(III) 配合物的简便途径，并进一步强调了具有良好局部电荷的轴向配位配体对于高性能 SMM 的需求。