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

Wen Yi Lee, Hsiang Hua Hsieh, Chun Chin Hsieh, Hon Man Lee, Gene Hsiang Lee, Jui Hsien Huang, Tsun Cheng Wu, Shiow Huey Chuang

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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.

Original languageEnglish
Pages (from-to)1131-1137
Number of pages7
JournalJournal of Organometallic Chemistry
Issue number5
Publication statusPublished - 2007 Feb 1

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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