title: Imidazolin-2-iminato titanium complexes: synthesis, structure and use in ethylene polymerization catalysis.
abstract: The Staudinger reaction of the imidazolin-2-ylidenes, 1,3-di-tert-butylimidazolin-2-ylidene (1a), 1,3-diisopropylimidazolin-2-ylidene (1b), 1,3-diisopropyl-4,5-dimethylimidazolin-2-ylidene (1c), 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (1d) and 1,3-bis(2,6-diisopropylphenylimidazolin-2-ylidene (1e), with trimethylsilyl azide furnishes the corresponding N-silylated 2-iminoimidazolines 2a-e, which react with [(eta-C5H5)TiCl3] to afford half-sandwich cyclopentadienyl titanium complexes of the type [CpTi(L)Cl2] (3) (L = imidazolin-2-iminato ligand). Similarly, the reactions of 1,3-di-tert-butyl-2-(trimethylsilylimino)imidazoline (2a) with [(eta-tBuC5H4)TiCl3] results in the formation of [(eta-tBuC5H4)Ti(L)Cl2] (4) (L = 1,3-di-tert-butylimidazolin-2-imide). Bis(1,3-di-tert-butylimidazolin-2-iminato)titanium dichloride (5) is obtained from the reaction of two eq. of 2a with TiCl4. Treatment of 5 with methyllithium results in the formation of the corresponding dimethyl complex [L2Ti(CH3)2] (6), whereas [CpTi(L)(CH3)2] (7) is similarly obtained from 3a. The molecular structures of 3a, 3b, 3c, 3e x C7H8, 4 and 7 are reported revealing linearly coordinated imidazolin-2-iminato ligands together with very short Ti-N bond distances. All dichloro complexes (3a-e, 4 and 5) can be activated with methylaluminoxane (MAO) to give active catalysts for ethylene homopolymerization. In most cases, moderate to high activities are observed together with the formation of high (HMWPE) or even ultra high molecular weight polyethylene (UHMWPE).
authors.affiliation: Institut für Anorganische und Analytische Chemie, Technische Universität Carolo-Wilhelmina, Hagenring 30, D-38106, Braunschweig, Germany. matthias.tamm@tu-bs.de
authors.forename: Matthias
authors.initials: M
authors.lastname: Tamm
authors.forename: Sören
authors.initials: S
authors.lastname: Randoll
authors.forename: Eberhardt
authors.initials: E
authors.lastname: Herdtweck
authors.forename: Nina
authors.initials: N
authors.lastname: Kleigrewe
authors.forename: Gerald
authors.initials: G
authors.lastname: Kehr
authors.forename: Gerhard
authors.initials: G
authors.lastname: Erker
authors.forename: Bernhard
authors.initials: B
authors.lastname: Rieger
mesh_terms: D002384:Catalysis; D005030:Ethylenes / Q000737:chemistry*; D048289:Imidazolidines / Q000138:chemical synthesis*; D007097:Imines / Q000737:chemistry*; D008024:Ligands; D008094:Lithium / Q000737:chemistry; D015394:Molecular Structure; D008970:Molecular Weight; D009942:Organometallic Compounds / Q000138:chemical synthesis*; D011108:Polymers / Q000737:chemistry*; D014025:Titanium / Q000737:chemistry*
chemical_list: D005030:Ethylenes; D048289:Imidazolidines; D007097:Imines; D008024:Ligands; D009942:Organometallic Compounds; D011108:Polymers; C036216:ethylene; D008094:Lithium; D014025:Titanium