Titanocene catalysts, polystyrene

Various transition metal catalysts, including those based on Rh, Pt, Pd, Co, and Ti, have been bound to polymer supports—mainly through the phosphenation reaction described by Eq. 9-65 for polystyrene but also including other polymers, such as silica and cellulose, and also through other reactions (e.g., alkylation of titanocene by chloromethylated polystyrene). Transition-metal polymer catalysts have been studied in hydrogenation, hydroformylation, and hydrosilation reactions [Chauvin et al., 1977 Mathur et al., 1980]. 

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. 

Bonds et al. reported the preparation of polystyrene divinylbenzene copolymer resin supporting titanocene TiCp2Cl2. The catalyst efficiency is greater than a corresponding nonattached species [89]. 

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