Catalysis ethene polymerisation

Polymerisation by homogeneous chromium catalysis is overviewed while further developments of vanadium-siloxane ethene polymerisations are also available. Triflate or... 

Metallocenes, in combination with the conventional aluminum alkyl cocatalysts used in Ziegler systems, are indeed capable of polymerising ethene, but only at a very low activity. Only with the discovery and application of methylaluminoxane (MAO) it was possible to enhance the activity, surprisingly, by a factor of 10000 [113]. Therefore, MAO plays a crucial part in the catalysis with metallocenes. 

Treatment of [CpTiCl(dmpe)2] with one equivalent of MeLi affords [CpTi(Me)(dmpe)2]. This complex is an active catalyst for the oligomerisation of ethene to but-l-ene, 2-ethylbut-l-ene and 3-methylpent-l-ene. The mechanism of the catalysis is proposed to involve titanacyclopentane intermediates. The complex [Cp TiMe2][MeB(C6Fj)3] acts as both a Ziegler-Natta catalyst for the polymerisation of alkenes, such as ethene and propene, and as a carbocationic initiator for the polymerisation of election rich alkenes such as A -vinylcarbazole and vinyl ethers. It also polymerises styrene to syndiotactic polystyrene, probably via a carbocationic initiated polymerisation. 50... 

The reaction between [Cp2ZrCl2] and either EtMgCl or Et2Mg-dioxane has been investigated and complexes 49 and 50 have been obtained in the latter the alkene was best described as a C2H/ anion. The energy profile for ansa-bridged zirconocene Ziegler-Natta catalysis was obtained from experimental rate data. The Zr and Hf complexes 51 have been prepared and shown to polymerise ethene in the presence of The Zr complex 52 has been... 

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