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

A series of phenylenediamidinate rare earth metal complexes 1,4-C6H4[C(NR)(2)Ln(o-CH2C6H4NMe2)(2)](2) (R = 2,6-Pr-i(2)-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 LnCl(3) 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)(2)Ln{OC(CH2C6H4NMe2-o)NPh}(2)(THF)](2) (Ln = Y (3a), Lu (3b)) and 1,4-C6H4[C(NR)(2)Ln{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 e-caprolactone polymerization; for the former a synergistic effect between two metal centers is observed.