Titanocene catalysts, polystyrene activities

Solid-phase supports used in combinatorial chemistry were used to prepare a cross-linked polystyrene bead containing a tetraethylene glycol spacer. The p-nitrosulfonate derivative of the polymer was substituted with NaCsHMesEt to form a supported cyclopentadiene, which was allowed to react with CpTiCls, making a tethered titanocene (Scheme 26). ° With MAO, this polymerizes ethylene with relatively low activity (41 g/mmol catalyst h) forming polymer with a noodle-like morphology. 

Ti(0-Z50-Pr)4 complexes on polystyrene with chiral groups are active in asymmetric epoxidation of geraniol by TBHP to (iS, -2,3-epoxygeraniol [145]. The enantiomeric excess reaches 66%. Recycling of the catalyst leads to a small decrease of asymmetric induction (loss of one-third of activity after five regeneration cycles). There are sparse data on epoxidation of cyclohexene and cyclooctene in the presence of immobilized titanocene, zirconocene and hafhocene [3]. 

Half-titanocenes such as Cp TIF3, Cp Ti(OMe)3, and IndTlCb are efficient catalyst precursors for syndiospecific styrene polymerization, as described above [9-11]. However, these catalyst precursors showed low catalytic activities and the resultant polymers in the ethylene/styrene copolymerization afforded a mixture of PE, syndiotactic polystyrene (SPS), and the copolymer... 

The presumed 14 electron Ti(C5Me5)(2,4-C7Hn), Ti(Ph2CH)2, and Ti(Ph2C-SiMc3)2 complexes (Section IIIA), as well as a variety of other open and half-open titanocenes, have been reported to yield, upon activation with MAO and/or poorly coordinating borate ions, catalysts for the polymerization of ethylene/a-olefin mixtures, styrene, vinylcyclohexane, vinylcyclohexene, butadiene, and related spedes." The polystyrene was isolated predominately in the syndiotactic form. 

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