Phenylene‐bridged β‐Ketoiminate Dilanthanide Aryloxides: Synthesis, Structure, and Catalytic Activity for Addition of Amines to Carbodiimides

The synthesis and reactivity of a series of bimetallic lanthanide aryloxides stabilized by a p-phenylene-bridged bis(-ketoiminate) ligand is presented. The reaction of 1,4-diaminobenzene with acetylacetone in a 1:2.5 molar ratio in absolute ethanol gave the compound 1,4-bis(4-imino-2-pentanone)benzene (1) (LH2) in high yield. Compound 1 reacted with (ArO)(3)Ln(THF)(2) (ArO = 2,6-tBu(2)-4-MeC6H2O, THF = tetrahydrofuran) in a 1:2 molar ratio in THF, after workup, to give the corresponding dilanthanide aryloxides L[Ln(OAr)(2)(THF)](2) [Ln = Yb (2), Y (3), Sm (4), Nd (5), La (6)] in high isolated yields. Compound 1 and complexes 2-6 were fully characterized, including X-ray crystal structure analyses for complexes 2, 3, 5, and 6. Complexes 2-6 can be used as efficient pre-catalysts for catalytic addition of amines to carbodiimides, and the ionic radii of the central metal atoms have a significant effect on the catalytic activity with the increasing sequence of La (6) < Nd (5) approximate to Sm (4) < Y (3) approximate to Yb (2). The catalytic addition reaction with 2 showed a good scope of substrates including primary and secondary amines.