161994-85-0Relevant articles and documents
Phosphorus-bridged metallocenes: New homogeneous catalysts for the polymerization of propene
Schaverien, Colin J.,Ernst, Rene,Terlouw, Wim,Schut, Peter,Sudmeijer, Olof,Budzelaar, Peter H.M.
, p. 245 - 256 (2008/10/09)
The synthesis of a new class of metallocenes for the syndiospecific, aspecific and isospecific polymerization of propene is reported. This has been achieved by the incorporation of a phosphorus linking the cyclopentadienyl-type rings. The catalyst precursors, syndiospecific PhP(fluorenyl-Cp)ZrCl2 (2), aspecific PhP(fluorenyl)2ZrCl2 (4), and isospecific PhP(indenyl)2ZrCl2 (5), RP(2-Me,4-Ph-indenyl)2ZrCl2 (R = Ph (6); R = (i)Pr (7)) were prepared. Compound 2, after activation by methylaluminoxane (MAO), in LIPP at 67°C affords syndiotactic polypropene (s-PP) with an activity of 155 kg s-PP/g Zr · h. The physical properties of the s-PP (stereoregularity and molecular weight) are similar to that of conventional carbon-bridged systems. Ab initio calculations on model compounds assisted in rationalizing the high syndiospecificity of 2 in contrast to the much poorer stereoregularity of closely related Me2Si(fluorenyl-Cp)ZrCl2. Aspecific metallocene 4, after activation with MAO, affords high molecular weight atactic-PP, albeit with a low activity. Metallocenes 6 and 7, activated by MAO, afford isotactic polypropene (i-PP) with extremely high stereoregularity (> 98% mmmm pentads), melting points 156-160°C and molecular weights tunable in the range 250,000-1,100,000. Activities of up to 580 kg i-PP / g Zr · h for 6/MAO (LIPP, 67°C, 37000 equiv. MAO) and 1265 kg i-PP/g Zr · h for 7/MAO (LIPP, 50°C, 37000 equiv. MAO) have been obtained.
Silylene-bridged fluorenyl-containing ligands and zirconium complexes with C1 and Cs symmetry: general synthesis and olefin polymerization catalysis
Chen, You-Xian,Rausch, Marvin D.,Chien, James C. W.
, p. 1 - 10 (2007/10/02)
A variety of new silylene-bridged fluorenyl-containing ligands has been synthesized with good yields via a convenient synthetic route.Two dimethylsilylene-bridged (η5-indenyl)(η5-fluorenyl) (1) and (η5-cyclopentadienyl)(η5-fluorenyl) (2) zirconocene dichlorides with C1 and Cs molecular symmetry have also been prepared.Upon activation with methyl aluminoxane, the former produced a polypropylene of high molecular weight, but with low activity and isotacticity.The latter catalyzed non-stereospecific propylene polymerization without any zyndiotactic tendency, but with 40 and 20 times greater ethylene and propylene activity respectively than the former catalytic system.Keywords: Zirconium; Olefin; Polymerization catalysis; Fluorenyl ligands