Synthesis, Structure, and Reactivity of Monoguanidinate Rare-Earth Metal Aminobenzyl Enolate Complexes

Two monoguanidinate rare-earth metal aminobenzyl enolate complexes LRE(CH2C6H4NMe2-o)(OCH=CH2)(THF) (L = (PhCH2)(2)NC(NC(6)H(3)iPr(2)-2,6)(2); RE = Y (1a), Lu (1b)) were synthesized via two pathways of the ring-opening of THF, and their reactivities with some molecules were also explored. Reaction of complex 1a with iPrNCNiPr gave the insertion product LY[(NiPr2)(2)CCH2C6H4NMe2-o](OCH=CH2)(THF) (2). Whereas, in the case of PhNCS, LY[SC(CH2C6H4NMe2-o)NPh](OCH=CH2)(THF) (3) and the ligands redistribution binuclear yttrium enolate complex [LY(mu-OCH=CH2)(OCH=CH2)](2) (4) were obtained. The protonolysis products LY(NHPh)(OCH=CH2)(THF)(2) (5), LY(NHPh)(2)(THF)(2) (6) and LY(NPh2)(OCH=CH2)(THF)(2) (7) were achieved by reaction of 1a with arylamine. Moreover, the THF ring-opening insertion products with unique structures {LY[O(CH2)(4)PPh2][mu-O(CH2)(4)PPh2]}(2) (8) and {LY(SCH2C6H4NMe2-o)[mu-O(CH2)(4)SCH2C6H4NMe2-o]}(2) (9) were afforded through reactions of complex 1a with diphenylphosphine and elemental sulfur. It was the first example of THF activation promoted by rare-earth metal thiolate complex. And some interesting chemical transformations were observed in our work. Complexes 1 could also serve as efficient initiators in the ring-opening polymerization of rac-lactide.