1196785-69-9Relevant academic research and scientific papers
Zirconium and hafnium complexes supported by linked bis(β- diketiminate) ligands: Synthesis, characterization and catalytic application in ethylene polymerization
Gong, Shaogang,Ma, Haiyan,Huang, Jiling
experimental part, p. 8237 - 8247 (2010/03/04)
Zirconium and hafnium complexes bearing new 1,2-ethanediyl- or 1,3-propanediyl-linked bis(β-diketiminate) ligands, [{CnH 2n-(BDIAr)2}MCl2] (Ar = 2,6-Me 2-C6H3, 2,6-Cl2-C6H 3, 2,6-iPr2-C6H3; M = Zr, n = 2 (4a-c), n = 3 (5a-c); M = Hf, n = 2 (6b)), were synthesized via the reaction of MCl4·2THF and one equivalent of dilithium salt of the corresponding ligand. Distorted trigonal prismatic and octahedral coordination geometries as well as C1-symmetric structures are found for zirconium complexes 4c and 5c in the solid state. Variable temperature 1H NMR spectra indicated the fluxional nature of 4a and 5a in solution. Upon activation with methylaluminoxane (MAO), all these complexes except hafnium complex 6b displayed moderate catalytic activities for ethylene polymerization. 1,2-Ethanediyl-linked complexes 4a and 4b are generally more active than their 1,3-propanediyl-linked analogues. The substituents at the ortho-positions of the phenyl rings have different effect on the catalytic activities of 1,2-ethanediyl-linked series or 1,3-propanediyl-linked series. It is noteworthy that even at a low Al/Zr molar ratio of 500, the catalytic activities of these zirconium complexes could be retained. Polyethylenes with broad molecular weight distributions (MWD = 15.3-20.3) were produced, which might result from the fluxional character of the zirconium complexes. The linear structure of obtained polyethylenes was further determined by 13C NMR spectroscopy and DSC analysis. The Royal Society of Chemistry 2009.
