title: Trinuclear and tetranuclear magnesium alkoxide clusters as highly active initiators for ring-opening polymerization of L-lactide.
abstract: Trinuclear and tetranuclear magnesium alkoxide clusters supported by bulky phenolates with triangular or rhombic structures were readily synthesized in acceptable yields via the reaction of 2-N,N-dimethylaminoethanol/methoxyethanol, different phenols, and dibutylmagnesium. These complexes have been characterized using (1)H and (13)C NMR, elemental analyses, and X-ray crystallography. The experimental results indicate that these clusters are efficient and excellent initiators for the ring-opening polymerizations (ROPs) of l-lactide (LA) and afford polylactides with desired molecular weights and narrow polydispersity indexes (PDIs). Complex 2 can even catalyze the ROP of 4000 equiv of l-lactide in 1 min in a controlled model. Kinetic studies indicate that the polymerization is first-order for both the trinuclear magnesium complex 3 and LA. However, for the tetranuclear magnesium complex 5, the polymerization rate is first order for 5 and second order for LA.
authors.affiliation: Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University , Lanzhou 730000, People's Republic of China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Gao
authors.forename: Zhongran
authors.initials: Z
authors.lastname: Dai
authors.forename: Jinjin
authors.initials: J
authors.lastname: Zhang
authors.forename: Xinxian
authors.initials: X
authors.lastname: Ma
authors.forename: Ning
authors.initials: N
authors.lastname: Tang
authors.forename: Jincai
authors.initials: J
authors.lastname: Wu
mesh_terms: D000438:Alcohols / Q000737:chemistry*; D004146:Dioxanes / Q000737:chemistry*; D007700:Kinetics; D008274:Magnesium / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D058105:Polymerization
chemical_list: D000438:Alcohols; D004146:Dioxanes; C091880:dilactide; D008274:Magnesium