Synthesis, structure and reactivity of dinuclear rare earth metal bis(o-aminobenzyl) complexes bearing a 1,4-phenylenediamidinate co-ligand

Abstract

A series of phenylenediamidinate rare earth metal complexes 1,4-C₆H₄[C(NR)₂Ln(o-CH₂C₆H₄NMe₂)₂]₂ (R = 2,6-ⁱPr₂-C₆H₃, Ln = Y (2a), Lu (2b), Sc (2c)) were synthesized by deprotonation of 1,4-C₆H₄[C(NR)(NHR)]₂ (1) with two equivalents of n-BuLi followed by reacting with two equivalents of anhydrous LnCl₃ and subsequently four equivalents of Li(o-CH₂C₆H₄NMe₂), or by protolysis of [Ln(o-CH₂C₆H₄NMe₂)₃] with 0.5 equivalent of 1 in THF or toluene. Treatment of complexes 2a and 2b with four equivalents of phenyl isocyanate and phenyl isothiocyanate gave the corresponding insertion products 1,4-C₆H₄[C(NR)₂Ln{OC(CH₂C₆H₄NMe₂-o)NPh}₂(THF)]₂ (Ln = Y (3a), Lu (3b)) and 1,4-C₆H₄[C(NR)₂Ln{SC(CH₂C₆H₄NMe₂-o)NPh}₂]₂ (Ln = Y (4a), Lu (4b)), respectively. The structures of 1, 3b, and 4a were established by X-ray diffraction studies. Complexes 2 show high activity for rac-lactide and ε-caprolactone polymerization; for the former a synergistic effect between two metal centers is observed.