Rare earth metal complexes anchored on a new dianionic bis(phenolate)dimethylamineCyclam ligand

A new bis(phenol)dimethyltetraazamacrocycle, 1,8-bis(2-hydroxy-3,5-di-tert-butylbenzyl)-4,11-dimethyl-1,4,8,11-tetraazacyclotetradecane (H2{(tBu2PhO)2Me2Cyclam}) (1), is described. Deprotonation of 1 with sodium or potassium hydrides afforded Na2{(tBu2PhO)2Me2Cyclam} (2) and K2{(tBu2PhO)Me2Cyclam} (3), respectively. Reactions of 2 or 3 with yttrium or lanthanide trichlorides led to the formation of neutral rare earth metal complexes of general formula [{(tBu2PhO)2Me2Cyclam}LnCl] (Ln = Y (4), La (5), Sm (6), Yb (7)) in moderate to high yields. The molecular structures of 4–7 were determined by single-crystal X-ray diffraction analysis and reveal that the ligand's denticity depends on the size of the metal ions. The smaller Y3+ and Yb3+ lead to distorted octahedral geometries where the dianionic ligand acts as pentadentate, while the larger ions, La3+ and Sm3+, form capped trigonal prismatic complexes with the cyclam derivative acting as a hexadentate chelator.

Graphical abstractYttrium and lanthanide (La, Sm, Yb) complexes supported by a dianionic dimethyl bis(phenolate) cyclam ligand are described. The molecular structures reveal that the ligand's denticity depends on the metal radii.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A new cyclam-based bis(phenol), H2{(tBu2PhO)2Me2Cyclam}, is reported. ► The sodium ions in Na2{(tBu2PhO)2Me2Cyclam}(THF)2 are non-equivalent. ► [M{(tBu2PhO)2Me2Cyclam}Cl] (M = Y, La, Sm, Yb) complexes are described. ► The ligand is hemilabile: it binds κ5-N3O2 to Y and Yb and κ6-N4O2 to La and Sm.