Exploring the Magnetism of <scp>C₅</scp>/<scp>C₂B₃</scp> Heteroleptic Organolanthanide Sandwiches

Comprehensive Summary Two families of cyclopentadienyl (Cp)/carboranyl heteroleptic sandwiched organolanthanide complexes, namely [Ln{ η 5 : σ ‐Me 2 C(C 5 H 4 )(C 2 B 10 H 10 )} 2 ][Li(DME) 3 ] ( 1Ln , Ln = Tb, Dy, Ho, Er) and [2‐THF‐2'‐( μ 2 ‐Cl)Li(THF) 3 ‐2,2'‐Ln( nido ‐1,7‐C 2 B 9 H 11 )Cp*] ( 2Dy ), were synthesized. Family of 1Ln has been proposed based on the mixing‐ligands idea by linking Cp and nido ‐dicarborllide. However, the carborane cage of [Me 2 C(C 5 H 4 )(C 2 B 10 H 10 )] 2− deprotons and forms a mono‐C − anion rather than deboron to form dicarborllide dianion. Hence, the family of 1Ln 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 1Dy and 1Tb show field‐induced slow magnetic relaxation behavior below 10 K. Inspired by 1Ln , the free pentamethylcyclopentadienyl (Cp* − ) and nido ‐dicarborllide ligands are used to sandwich central Dy 3+ ion, achieving heteroleptic complex 2Dy . The bending angle by linking the centroid of Cp* − , Dy 3+ and C 2 B 3 2− in 2Dy is increased to 132.8(1)°. As such, the effective energy barrier for magnetic reversal ( U eff ) and magnetic blocking temperature T B (ZFC) are both increased ( U eff = 616(10) K; T B = 6 K). The effort of further enhancing U eff and T B in such heteroleptic organolanthanide sandwiches should rely on keeping increasing the ligand axiality.