Monoalkyllanthanide Complexes with New β-Diketiminato Derivative Dianionic Ligands

A new class of β-diketiminato derivative dianionic ligands was designed, and three ligand precursors [CH3C(ArNH)CHC(CH3)(NCH2CH2-NHR)] (Ar = 2,6-(iPr)2C6H3; R = tBu (H2L1), 2,6-(CH3)2C6H3 (H2L2), 2,6-(iPr)2C6H3 (H2L3)) were synthesized. The alkane elimination reactions between these ligand precursors and Ln(CH2SiMe3)3(THF)n provided eight five-coordinate monoalkyllanthanide complexes, in which the ligand serves as a tridentate dianionic donor, with one −CH2SiMe3 and one THF molecule completing the five-coordinate center. These monoalkyl complexes exhibited low to very high catalytic activities for intramolecular hydroamination of 2,2-dimethyl-1-aminopent-4-ene. The catalytic activity increased with increasing metal ion size. For the Nd complex, 98% yield was obtained in 1 h at 60 °C with 0.5 mol % catalyst loading.