Dramatic enhancement of the stability of rare-earth metal complexes with α-methyl substituted N, N-dimethylbenzylamine ligands

Abstract

Stepwise substitution of benzylic CH 2 protons in ortho-metallated N, N- di methyl benzyl amine (dmba) ligands leads to chiral ortho-metallated N, N,α- tri methyl benzyl amine (tmba) and cumyl- N, N- dimethyl amine (cuda) ligands. These larger ligands with less or no acidic protons in benzylic position prove to stabilize some of those homoleptic tris-aryls of the larger (middle) and largest (early) rare-earth metal cations, for which such tris-aryl or tris-dmba complexes could not be synthesized so far. The syntheses, characterization and crystal structures of [Li(cuda)], [(tmba) 2Lu(μ-Cl)] 2 ( 1), [(tmba) 2Y(μ-Cl)] 2 ( 2), [Y(tmba) 3] ( 3), [Dy(tmba) 3] ( 4), [Nd(tmba) 3] ( 5), [Sm(tmba) 3] ( 6), and [Sm(cuda) 3] ( 7) are reported, trends in complex stability are discussed.