Synthesis of rare-earth metal complexes with a morpholine-functionalized beta-diketiminato ligand and their catalytic activities towards C-O and C-N bond formation

Unusual tridentate beta-diketiminato rare-earth metal chlorides LRECE(mu-Cl)(2)Li(THF)(2) (RE = Y (1a), Yb (1b), and Lu (1c); L = MeC(NDipp)CHC(Me)N(CH2)(2)NC4H8O; Dipp = 2,6-(Pr2C6H3)-Pr-i) and the corresponding dialkyl complexes LRE(CH2SiMe3)(2) (RE = Y (2a), Yb (2b), and Lu (2c)) were prepared by reaction of a morpholine-functionalized beta-diketiminato proligand HL with anhydrous RECE3 and rare-earth metal trialkyl complexes RE(CH2SiMe3)(3)(THF)(2), respectively. In 1 and 2, the morpholine moiety displayed a stable chair conformation and the resulting ligand coordinated to the rare-earth metal ion in a [NNN]-tridentate chelating fashion. Further studies demonstrated that these dialkyl complexes showed high activity towards the catalytic formation of C-O and C-N bonds in the alcoholysis of isothiocyanates and aminolysis of epoxides. A series of O-thiocarbamate derivatives were achieved in good to excellent yields by reaction of various alcohols with aromatic and aliphatic-substituted isothiocyanates at room temperature. In addition, under solvent-free conditions, the ring-opening reaction of terminal and internal epoxides with arylamines yielded the corresponding beta-amino alcohols with excellent regioselectivity. More importantly, a novel beta-diketiminato/anilido yttrium alkyl complex LY(NHDipp)(CH2SiMe3) (5a) was isolated and characterized by the stoichiometric reaction of 2a with diisopropylaniline.