Scandium and yttrium phosphasalen complexes as initiators for ring-opening polymerization of cyclic esters.

摘要: The synthesis and characterization of novel scandium yttrium phosphasalen complexes is reported, where refers to two different bis(iminophosphorane) derivatives the more ubiquitous salen ligands. activity as initiators for ring-opening polymerization cyclic esters presented. are inactive lactide but slow controlled e-caprolactone polymerization. lack toward exhibited by these compounds probed, a rare example single-monomer insertion product, unable undergo further reactions with lactide, identified. In contrast, analogous complex very active initiator rac-lactide (kobs = 1.5 × 10–3 s–1 at 1:500 [yttrium initiator]:[rac-lactide], 1 M overall concentration in THF 298 K). addition being fast initiator, also maintains excellent levels polymeri...