Diamido-Ether Actinide Complexes as Initiators for Lactide Ring-Opening Polymerization

Abstract

The synthesis and characterization of a series of new diamido-ether actinide(IV) alkoxide complexes are reported. Addition of 2 equiv of LiOiPr to [tBuNON]ThCl5Li3·DME ([tBuNON]2– = [(tBuNSiMe2)2O]2–) in toluene gives [tBuNON]Th(OiPr)3Li·DME (1-DME). Recrystallization of 1-DME from diethyl ether gives [tBuNON]Th(OiPr)3Li·Et2O (1-Et2O). The addition of 2 equiv of LiOiPr to {[tBuNON]UCl2}2 gives {[tBuNON]U(OiPr)2}2 (2). If KOtBu is used instead, the product is {[tBuNON]U(OtBu)}2 (3). The reaction of 2 equiv of KOtBu with [iPr2PhNCOCN]ThCl2·DME ([iPr2PhNCOCN]2– = [(2,6-iPr2PhNCH2CH2)2O]2–) gives [iPr2PhNCOCN]Th(OtBu)2 (4), while addition of 1 equiv of KOtBu to [iPr2PhNCOCN]UCl3Li·THF results in [iPr2PhNCOCN]U(OtBu)Cl (5). Complexes 1–5 as well as the previously reported diamido actinide dialkyl complexes [tBuNON]An(CH2SiMe3)2 (An = Th (6), U (7)) and [iPr2PhNCOCN]An(CH2SiMe3)2 (An = Th (8), U (9)) were evaluated as initiators for the ring-opening polymerization (ROP) of l-lactide (l-LA) and racemic lactide (...