Early transition metal complexes bearing a C-capped tris(phenolate) ligand incorporating a pendant imine arm: Synthesis, structure, and ethylene polymerization behavior

Article abstract of DOI:10.1021/ic702506w

The ligand 3-[2,2′-methylenebis(4,6-di-tert-butylphenol)-5-tert- butylsalicylidene-(2,6-diisopropyl)phenylimine] (L¹H₃) was reacted with MCl₄ (M = Ti, Zr) or MCl₅ (M = Nb, Ta) to give complexes of the type [MCl₂(L¹H₂) ₂] (M = Ti (1); Zr (2)), [NbCl₃(L¹H)] (3), or [TaCl₄(L¹H₂)] (4), respectively. Single crystal X-ray diffraction of 1-4 revealed common iminium species resulting in zwitterionic complexes. Reaction of [V(Np-tol)(On-Pr)₃] with L¹H₃ afforded [{(VNp-tol)(L¹H)} ₂(μ-On-Pr)₂] (5), and a second complex [(VO) ₂(μ-O)(L³H)₂] (6) (L³H being derived from 3-[2,2′-methylenebis(4,6-di-tert-butylphenol)-5-tert- butylsalicylidene-p-tolylimine]). The condensation reaction between 3-[2,2′-methylenebis(4,6-di-tert-butylphenol)-5-tert-butyl-2- hydroxybenzaldehyde] (L⁰H₃) and o-phenylenediamine (1, 2-diaminobenzene) afforded two products: a pseudo-16-membered hydrogen bonded macrocyclic structure {1,2-bis-3-[2,2′-methylenebis(4,6-di-tert- butylphenol)-5-tert-butylsalicylidene-benzyldiimine]} (L⁵H ₆), or the benzimidazolyl bearing ligand (L⁶H ₃). The reaction of L⁵H₆ or L⁶H ₃ with [VO(On-Pr)₃] under varying conditions produced the complexes [(VO)(L⁵H₄)] (7), [(VO)₂(L ⁵H)] (8), or [VO(L⁶H₂)₂] (9). L ⁰H₃ was reacted with a number of anilines to give the proligands {3-[2,2′-methylenebis(4,6-di-tert-butylphenol)-5-tert- butylsalicylidene-R-imine]}, where R = NC₆H₅ (L ²H₃), NC₆H₄-Me (L³H ₃), and NC₆H₂-Me₃ (L ⁴H₃). Reactions of these ligands with [VO(On-Pr) ₃] formed bischelating complexes of the form [(VO)(L ^2-4H₂)₂] (10, 11, and 12, respectively). The reaction of L¹H₃ with trimethylaluminum led to a bis-aluminum complex {(AlMe₂)[AlMe(NCMe)]L¹} (13). The ability of complexes 1-12 to polymerize ethylene in the presence of an organoaluminum cocatalyst was investigated. Procatalysts 1 and 2 were found to produce negligible activities in the presence of dimethylaluminum chloride (DMAC) and the reactivator ethyltrichloroacetate (ETA), whereas 3 and 4 were found to be completely inactive for polymerization using a variety of different organoaluminum cocatalysts. Using the combination of DMAC and ETA, complexes 5-12 were found to be highly active catalysts; in all cases, the polymer formed was of high molecular weight linear polyethylene.