title: Aminopyridinate-FI hybrids, their hafnium and titanium complexes, and their application in the living polymerization of 1-hexene.
abstract: Based on two well-established ligand systems, the aminopyridinato (Ap) and the phenoxyimine (FI) ligand systems, new Ap-FI hybrid ligands were developed. Four different Ap-FI hybrid ligands were synthesized through a simple condensation reaction and fully characterized. The reaction of hafnium tetrabenzyl with all four Ap-FI hybrid ligands exclusively led to mono(Ap-FI) complexes of the type [(Ap-FI)HfBn2 ]. The ligands acted as tetradentate dianionic chelates. Upon activation with tris(pentafluorophenyl)borane, the hafnium-dibenzyl complexes led to highly active catalysts for the polymerization of 1-hexene. Ultrahigh molecular weights and extremely narrow polydispersities support the living nature of this polymerization process. A possible deactivation product of the hafnium catalysts was characterized by single-crystal X-ray analysis and is discussed. The coordination modes of these new ligands were studied with the help of model titanium complexes. The reaction of titanium(IV) isopropoxide with ligand 1 led to a mono(Ap-FI) complex, which showed the desired fac-mer coordination mode. Titanium (IV) isopropoxide reacted with ligand 4 to give a complex of the type [(ApH-FI)2 Ti(OiPr)2 ], which featured the ligand in its monoanionic form. The two titanium complexes were characterized by X-ray crystal-structure analysis.
authors.affiliation: Lehrstuhl Anorganische Chemie II, Universität Bayreuth, Universitätsstraße 30, NW I, 95440 Bayreuth (Germany).
authors.forename: Isabelle
authors.initials: I
authors.lastname: Haas
authors.forename: Thomas
authors.initials: T
authors.lastname: Dietel
authors.forename: Konstantin
authors.initials: K
authors.lastname: Press
authors.forename: Moshe
authors.initials: M
authors.lastname: Kol
authors.forename: Rhett
authors.initials: R
authors.lastname: Kempe
keywords: hafnium; ligand design; ligand effects; living polymerization; polymerization