Synthesis, structural characterization and catalytic property of group 4 metal complexes bearing novel salalen-type ligands

• Published in: Journal of organometallic chemistry Vol. 741-742; pp. 83 - 90
• Main Authors: Huang, Kun, Zhou, Sen, Zhang, Dao, Gao, Xiang, Wang, Quanrui, Lin, Yuejian
• Format: Journal Article
• Language: English
• Published: LAUSANNE Elsevier B.V 01.10.2013; Elsevier
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Chemistry, Organic; Crystal structure; Ethylene polymerization; Group 4 metal complex; Physical Sciences; Salalen ligand; Science & Technology; Group 4 metal complex; Ethylene polymerization; Salalen ligand; Crystal structure; MOLECULAR-WEIGHT; ZIRCONIUM COMPLEXES; HYDROPHOSPHONYLATION; TITANIUM COMPLEXES; ISOSPECIFIC POLYMERIZATION; OLEFIN POLYMERIZATION CATALYSIS; SALEN; SCHIFF-BASE; 1-HEXENE
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/j.jorganchem.2013.05.036

Reaction of novel salalen ligands trans-1-(2′-OH-3′,5′-tBu2C6H2CH2N(Me))-2-(2″-OH-3″,5″-R2-C6H2CHN)-cyclohexane (R = tert-Butyl, H2(La); R = Cl, H2(Lb); R = Br, H2(Lc); R = I, H2(Ld)) with appropriate group 4 metal precursors [MCl4(THF)2] (M = Ti, Zr, Hf) gave a family of complexes [Ti(La–d)Cl2] (1a–1d) and [M(La, c)Cl2] (M = Zr, 2a, c; M = Hf, 3a, c). X-ray single crystal analysis revealed that in the solid state these salalen group 4 metal complexes formed as single isomers with fac–mer geometry and the two chlorine groups are cis-oriented. Introducing the trans-1,2-cyclohexylene bridge and the electron-withdrawing effects of halide substituents improved the catalytic prosperity for ethylene polymerization. The titanium complexes 1a–d showed moderate activity of 37.2–110.0 kg/(molTi h atm) in the polymerization of ethylene using MAO as cocatalyst. Zirconium and hafnium complexes were almost inactive except 2a with a low activity of 4.4 kg/(molZr h atm). The high temperature 1H and 13C NMR analysis revealed that these polymers are vinyl-terminated low-molecular-weight linear polyethylene (Mn = 1800–3800 g mol−1; the vinyl selectivity is about 85–91 mol %). A series of group 4 metal complexes supported by novel trans-1,2-cyclohexylene bridged salalen ligands have been synthesized and confirmed by X-ray analysis. The salalen titanium complexes were active to catalyze ethylene polymerization with moderate activity with the MAO as cocatalyst, while salalen zirconium and hafnium complexes were almost inactive. [Display omitted] •New trans-1,2-cyclohexylene bridged salalen ligands containing halides (Cl, Br, I).•Five salalen group 4 metal complexes have been characterized by X-ray crystallography.•Titanium complexes are moderately effective catalysts for ethylene polymerization.