Exploring the Magnetism of C5/C2B3 Heteroleptic Organolanthanide Sandwiches.

Comprehensive Summary Two families of cyclopentadienyl (Cp)/carboranyl heteroleptic sandwiched organolanthanide complexes, namely [Ln{η5:σ‐Me2C(C5H4)(C2B10H10)}2][Li(DME)3] (<bold>1Ln</bold>, Ln = Tb, Dy, Ho, Er) and [2‐THF‐2'‐(μ2‐Cl)Li(THF)3‐2,2'‐Ln(nido‐1,7‐C2B9H11)Cp*] (<bold>2Dy</bold>), were synthesized. Family of <bold>1Ln</bold> has been proposed based on the mixing‐ligands idea by linking Cp and nido‐dicarborllide. However, the carborane cage of [Me2C(C5H4)(C2B10H10)]2− deprotons and forms a mono‐C− anion rather than deboron to form dicarborllide dianion. Hence, the family of <bold>1Ln</bold> features a dysprosocenium skeleton with extra two coordination of C− anions of carborllides. Such coordination geometry is more like a tetrahedron if abstracting the centroids of two coordinated Cp rings. In this cubic‐type geometry, no significant magnetic axiality is presented; only <bold>1Dy</bold> and <bold>1Tb</bold> show field‐induced slow magnetic relaxation behavior below 10 K. Inspired by <bold>1Ln</bold>, the free pentamethylcyclopentadienyl (Cp*−) and nido‐dicarborllide ligands are used to sandwich central Dy3+ ion, achieving heteroleptic complex <bold>2Dy</bold>. The bending angle by linking the centroid of Cp*−, Dy3+ and C2B32− in <bold>2Dy</bold> is increased to 132.8(1)°. As such, the effective energy barrier for magnetic reversal (Ueff) and magnetic blocking temperature TB (ZFC) are both increased (Ueff = 616(10) K; TB = 6 K). The effort of further enhancing Ueff and TB in such heteroleptic organolanthanide sandwiches should rely on keeping increasing the ligand axiality. [ABSTRACT FROM AUTHOR]