205759-36-0Relevant academic research and scientific papers
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.
PPh-bridged metallocene complexes of the type (C13H8-PPh-C13H8)MCl2 (M=Zr, Hf)
Alt, Helmut G.,Jung, Michael
, p. 127 - 131 (2007/10/03)
The synthesis and NMR spectroscopic characterization of new ansa-metallocene dichloride complexes of the type (C13H8-PPh-C13H8)MCl2 (M=Zr (5), Hf (6)) is reported The complexes can be activated with methylaluminoxane (MAO), and are then able to polymerize ethylene. In contrast to CR2 and SiR2 bridged derivatives, the PPh bridge increases the electron density of the system which leads to a drastic decrease in polymerization activities.
