title: Four- and five-coordinate aluminum ketiminate complexes: synthesis, characterization, and ring-opening polymerization.
abstract: A series of aluminum complexes featuring with the ketiminate ligand, OCMeCHCMeNHAr (Ar = 2,6-(i)Pr(2)C(6)H(3), 1), have been prepared and characterized spectroscopically and structurally. Reactions of 1 with trialkylaluminum in 1:1 or 1:2 molar ratio generate four- and five-coordinated aluminum complexes (OCMeCHCMeNAr)AlR(2) (R = Me (2); R = Et (3)) and (OCMeCHCMeNAr)(2)AlR (R = Me (4); R = Et (5)) in high yields. Similarly, reaction of AlCl(3) with 1 or 2 equiv of the lithiated 1 in toluene afforded bis(ketiminate) aluminum chloride complex, (OCMeCHCMeNAr)(2)AlCl (6) or (OCMeCHCMeNAr)AlCl(2) (7). Surprisingly, reacting 6 with 1 equiv of AgBF(4) in methylene/acetonitrile mix-solvents generates (OCMeCHCMeNAr)(2)AlF (8) in moderate yield. The structures of complexes 2-6 and 8 have been determined by X-ray crystallography. Complexes 2 and 3 both exhibit tetrahedron structures with the aluminum atom surrounded by oxygen and nitrogen atoms of chelating ketiminate and two alkyl groups. The mono- and bis-ketiminate aluminum complexes 2-5 have shown moderate activity toward the ring-opening polymerization of epsilon-caprolactone.
authors.affiliation: Department of Chemistry, National Changhua University of Education, Changhua, Taiwan 500.
authors.forename: Ru-Ching
authors.initials: RC
authors.lastname: Yu
authors.forename: Chen-Hsiung
authors.initials: CH
authors.lastname: Hung
authors.forename: Jui-Hsien
authors.initials: JH
authors.lastname: Huang
authors.forename: Horng-Yi
authors.initials: HY
authors.lastname: Lee
authors.forename: Jwu-Ting
authors.initials: JT
authors.lastname: Chen