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Title: Four- and five-coordinate Magnesium Compounds Containing Ketiminate Ligands. Synthesis and Characterization of L2Mg, L2Mg(LH), and L2Mg(Py), where L = MeC(O)CHC(NAr)Me
Authors: Lee, Wen-Yi;Hsieh, Hsiang-Hua;Hsieh, Chun-Chin;Lee, Hon-Man;Lee, Gene-Hsiang;Huang, Jui-Hsien;Wu, Tsun-Cheng;Chuang, Shiow-Huey
Contributors: 化學系
Keywords: Magnesium;Ketiminate;Caprolactone
Date: 2007-02
Issue Date: 2012-12-10T01:39:47Z
Publisher: Elsevier
Abstract: Magnesium complexes containing ketiminate ligands were synthesized and characterized. MgBu2 reacted readily in toluene with two equiv. of [MeC(O)CHC(NHAr)Me], where Ar = 2,6-diisopropylphenyl, to generate [MeC(O)CHC(NAr)Me]2Mg (1) in 43% yield. The four-coordinate magnesium compound 1 is very moisture sensitive and acts as a Lewis acid, accepting one equiv. of Lewis base to form five-coordinate magnesium compounds. Compound [MeC(O)CHC(NAr)Me]2Mg[MeC(O)CHC(NHAr)Me] (2) was obtained in 57% yield from the reaction in toluene of MgBu2 with three equiv. of [MeC(O)CHC(NHAr)Me]. Treatment of 1 with one equiv. of free ketimine ligands [MeC(O)CHC(NHAr)Me] also led to the formation of 2. The bulky η1-ketimine of 2 can be replaced with a less bulky Lewis base such as pyridine. Treatment of 1 with excess pyridine in toluene at ambient temperature led to the formation of compound [MeC(O)CHC(NAr)Me]2Mg[NC5H5] (3) as colorless crystalline solids in 51% yield. Compounds 1, 2, and 3 were characterized by NMR and X-ray crystallography. Compounds 2 and 3 showed no activity toward the polymerization of ε-caprolactone at 25 °C after 3 h. However, when the temperature was increased to 70 °C, compounds 2 and 3 efficiently catalyzed polymerization of ε-caprolactone to generate high molecular weight poly-ε-caprolactones. The polydispersity index (PDI) of these poly-ε-caprolactones is in the range 1.57–3.18.
Relation: Journal of Organometallic Chemistry, 692(5): 1131-1137
Appears in Collections:[Department of Chemistry] Periodical Articles

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