New anilinotropone-based titanium complexes: synthesis, characterization and application as catalysts for olefinpolymerization

Abstract

New titanium(IV) dichloride complexes containing 2-anilinotropone ligands have been synthesized and characterized. Bis(ligand)titanium dichloride complexes 1 and 2 were synthesized from reaction of TiCl₄(THF)₂ with 2 equivalents of the corresponding sodium salts of 2-(2,6-diisopropylanilino)tropone (L1) and 2-(2,3,4,5,6-pentafluoroanilino)tropone (L2), respectively. The mixed cyclopentadienyl–anilinotropone compound 3 was synthesized by reaction of the lithium salt of L2 with CpTiCl₃. The Cp-mixed μ-O bimetallic complex 4 was also isolated as a by-product owing to the adventitious presence of moisture. The molecular structures of 1–4 have been determined by single-crystal X-ray diffraction studies. Complexes 1 and 2 are isostructural and exhibit a C₂-symmetric octahedral geometry, with a trans (N,N), cis (O,O) arrangement in complex 1, but with a trans (O,O), cis (N,N) arrangement in complex 2. The Cp-mixed complex 3 has a distorted square-pyramidal structure with the Cp ligand in the apical position. Bimetallic complex 4 shows a similar coordination geometry for the five-coordinate titanium atom and a pseudo-tetrahedral coordination for the second metallic centre. All new complexes, when activated with methylaluminoxane, are active in the polymerization of ethylene and propene.