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

作者：Lee Wen Yi; Hsieh Hsiang Hua; Hsieh Chun Chin; Lee Hon Man; Lee Gene Hsiang; Huang Jui Hsien^*; Wu Tsun Cheng; Chuang Shiow Huey

来源：Journal of Organometallic Chemistry, 2007, 692(5): 1131-1137.

DOI：10.1016/j.jorganchem.2006.11.015

• magnesium
• ketiminate
• caprolactone

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](2)Mg (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](2)Mg[MeC(O)CHC(NHAr)Me] (2) was obtained in 57% yield from the reaction in toluene of MgBu-, 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 eta(1)-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](2)Mg[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 r-caprolactone at 25 degrees C after 3 h. However, when the temperature was increased to 70 degrees C, compounds 2 and 3 efficiently catalyzed polymerization of epsilon-caprolactone to generate high molecular weight poly-epsilon-caprolactones. The polydispersity index (PD1) of these poly-epsilon-caprolactones is in the range 1.57-3.

• 出版日期2007-2-1