Polymerization activity cyclopentene

TABLE 1. ROMP of cyclopentene (CPE) with the carbyne tungsten (VI) complexes Cl3(dme)WHC Bu (A) and ( BuO)3W=C Bu (B) in different solvents and in bulk pa = polymerization activity [mmol CPE mmol catalyst h ] (calculated from the turnover of monomer after 1 h), trans = trans content of doublebonds (measured via C NMR spectroscopy), temperature 25°C. 

Table 2 compares some different metallocenes for the polymerization of cyclopentene. There were found good yields for the isotactic working bis(indenyl)zirconocene, and low activities for the atactic working Cp2ZrCl2 and the syndiotactic working complex [Ph2C(Cp)(Flu)]ZrCl2. ... 

McLain et polymerized cyclopentene by late transition metal catalysts using MAO and borate-activated nickel and palladium diimine complexes. The nickel diimine complexes produce crystalline materials showing a ds-1,3 enchainment with a melting point of 240-330 °C. The hydroligomers were mainly atactic. Palladium catalysts gave pure atactic polymers. It is also possible to polymerize substituted cyclopentenes such as 3-methyl- or 3-ethyl-cyclopentene. 

The active species in propagation is a transition metal carbene with a vacant d-orbital. For polymerization of cyclopentene by tungsten-based catalysts the overall propagation reaction can be represented by... 

Among the first 18-electron (18e) Fischer-type metal carbene complexes to be used as part of an olefin metathesis catalyst system were W[=C(OMe)Et](CO)5 with BU4NCI (for pent-l-ene)79, and W[=C(OEt)Bu](CO)5 with TiCLt (for cyclopentene)80. These complexes may also be activated thermally, e.g. for the polymerization of alkynes81, or photochemically, e.g. for the ROMP of cycloocta-1,5-diene82. The essential requirement is that a vacancy be created at the metal centre to allow the substrate to enter the coordination sphere. Occasionally the substrate may itself be able to displace one of the CO ligands. 

The cyclopentene derivatives 89348, 92349 and 93350 do not appear to undergo ROMP, probably because their free energy of polymerization is positive. However, the fact that 1% of 89 can completely inhibit the polymerization of 90 and 91 indicates that it is likely to add preferentially to the active site forming the head carbene complex, [W](=CMeCH2CH2CH2CH=CHR), which is then unable to add any of these three monomers. It should be capable of copolymerization with norbornene. 

Hydrocyanation. Although 2-carbomethoxy-2-cyclopentene-l-one (2) is prone to polymerization, it reacts smoothly with diethylaluminium cyanide to give the adduct 3. This product has the carbon skeleton of sarkomycin (7), an antibiotic active against ascites-type tumors. Selective manipulation of the functionaTgroups resulted in the first regiospecific synthesis of 7. ... 

Table 4 shows polymerization conditions and properties of crystalline polymers of cyclobutene, cyclopentene, norbomene, and tetracyclododecene produced by zirconocenes. The activities for the polymerization of cycloalkenes are significantly lower than for ethylene. The melting points are surprisingly high they were found to be 395 °C for polycyclopentene and over 400 °C for the others the decomposition temperatures lie in the same range. 

The co-polymerization of ethylene and 2-butene with the McConville catalyst 87 has been reported. NMR analysis of the co-polymer indicated that only the tram-isomer of 2-butene was incorporated.1 6 Ethylene and cylopentene have been co-polymerized with the MAO-activated complex 138 working at very low ethylene pressure.605 The almost regularly alternating poly( ethylene- //-m-l,2-cyclopentene) co-polymer exhibited a T of 10 °C. This copolymer is a crystalline plastomer with high structural disorder.1237 Furthermore, multi-block co-polymers were synthesized by changing the ethylene pressure during polymerization. This way, the various blocks are characterized by a different amount of cyclopentene units.605... 

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