The Facile Synthesis of Lithium 2‐R‐Hydroquinolinide Complexes and Their High Activity toward ROP of ε ‐Caprolactone

Four lithium 2‐R‐hydroquinolinide complexes [1‐(2‐(R)‐C 9 H 7 )NLi · THF 2 ] 2 ( 1 R = Me, 2 R = n Bu) and [1‐(8‐(Me)‐2‐(Bu n )‐C 9 H 6 )NLi · X] 2 ( 3 X = THF, 4 X = Et 2 O) were prepared by the nucleophilic addition reaction of quinoline and 8‐methylquinoline with MeLi or Bu n Li, respectively. All complexes have been characterized through NMR spectroscopy. Complexes 2–4 were determined by X‐ray crystallography. Interestingly, Li atom in 1 and 2 is tetracoordinate, whereas Li atom in 3 and 4 is three‐coordinate. All these complexes showed super‐high activity for the ring‐opening polymerization (ROP) of ε ‐caprolactone in both the absence and presence of BnOH at 35 °C in CH 2 Cl 2 . By the 1–4 catalytic systems with or without BnOH as a co‐initiator, the ROP of ε ‐CL proceeded well in a living manner as evidenced by the predictable molecular weights, narrow molecular weight distributions, and kinetic studies. MALDI‐TOF MS analysis revealed that the resultant PCL showed a cyclic structure in the absence of BnOH and a BnO – capped linear structure was observed in the presence of BnOH.