Exploring the Magnetism of C₅/C₂B₃ Heteroleptic Organolanthanide Sandwiches

Abstract

Comprehensive Summary:Two families of cyclopentadienyl (Cp)/carboranyl heteroleptic sandwiched organolanthanide complexes, namely [Ln{ η ⁵: σ-Me ₂C(C ₅H ₄)(C ₂B ₁₀H 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 ₂B ₉H 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 ₂C(C ₅H ₄)(C ₂B ₁₀H 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 ₂B 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.

Keywords

Single-molecule magnets / Heteroleptic sandwiched complexes / nido-Dicarborllide / Lanthanides / Cyclopentadienyl

RIGHTS & PERMISSIONS

2024 SIOC, CAS, Shanghai, & WILEY-VCH GmbH