Olefin complexes copolymerization with

It has been shown by Barb and by Dainton and Ivin that a 1 1 complex formed from the unsaturated monomer (n-butene or styrene) and sulfur dioxide, and not the latter alone, figures as the comonomer reactant in vinyl monomer-sulfur dioxide polymerizations. Thus the copolymer composition may be interpreted by assuming that this complex copolymerizes with the olefin, or unsaturated monomer. The copolymerization of ethylene and carbon monoxide may similarly involve a 1 1 complex (Barb, 1953). 

Chemical Properties. Higher a-olefins are exceedingly reactive because their double bond provides the reactive site for catalytic activation as well as numerous radical and ionic reactions. These olefins also participate in additional reactions, such as oxidations, hydrogenation, double-bond isomerization, complex formation with transition-metal derivatives, polymerization, and copolymerization with other olefins in the presence of Ziegler-Natta, metallocene, and cationic catalysts. All olefins readily form peroxides by exposure to air. 

Water-soluble dicationic palladium(II) complexes [(R.2P(CH2)3PR.2)Pd-(NCMe)2][BF4]2 proved to be highly active in the carbon monox-ide/ethene copolymerization under biphasic conditions (water-toluene). In the presence of an emulsifier and methanol as activator, the catalytic activity increased by a factor of about three. Also higher olefins could be successfully incorporated into the copolymerization with CO and the terpolymerization with ethene and CO.184... 

Palladium(II) complexes possessing bidentate ligands are known to efficiently catalyze the copolymerization of olefins with carbon monoxide to form polyketones.594-596 Sulfur dioxide is an attractive monomer for catalytic copolymerizations with olefins since S02, like CO, is known to undergo facile insertion reactions into a variety of transition metal-alkyl bonds. Indeed, Drent has patented alternating copolymerization of ethylene with S02 using various palladium(II) complexes.597 In 1998, Sen and coworkers also reported that [(dppp)PdMe(NCMe)]BF4 was an effective catalyst for the copolymerization of S02 with ethylene, propylene, and cyclopentene.598 There is a report of the insertion reactions of S02 into PdII-methyl bonds and the attempted spectroscopic detection of the copolymerization of ethylene and S02.599... 

Scheme 11 Catalyst deactivation routes in copolymerizations with polar olefins a P-elimination of a leaving group to afford allylic or dimeric species, b poisoning by N-complexation in the attempted copolymerization of acrylonitrile...

In contrast to the free-radical polymerizations, there have been relatively few studies on transition metal catalysed polymerization reactions in water. This is largely due to the fact that the early transition metal catalysts used commercially for the polymerization of olefins tend to be very water-sensitive. However, with the development of late transition metal catalysts for olefin polymerizations, water is beginning to be exploited as a medium for this type of polymerization reaction. For example, cationic Pd(II)-bisphosphine complexes have been found to be active catalysts for olefin-CO copolymerization [21]. Solubility of the catalyst in water is achieved by using a sulfonated phosphine ligand (Figure 10.5) as described in Chapter 5. 

Although the structures of these copolymers were not indicated, it is probable that the olefin and polar monomer are alternating units in accordance with the scheme in Reaction 23. It is also probable that the presence of excess polar monomer in the copolymer, as indicated in some examples, results from copolymerization of the polar monomer-com-plexed polar monomer complex or with the olefin-complexed polar monomer complex or concurrent homopolymerization of the two complexes. 

Hirooka has proposed that the products are alternating copolymers produced through complex copolymerization and that the latter process differs from that of Imoto and Otsu (30, 33, 34) in which a free radical initiator is necessary for the random copolymerization of olefins with acrylonitrile or methyl methacrylate in the presence of zinc chloride. 

As previously discussed, the copolymers produced in the zinc chloride-free radical system are not necessarily random copolymers but are probably the result of the copolymerization of the acrylonitrile-complexed acrylonitrile complex with the olefin-complexed acrylonitrile complex. Further, the olefin-alkylaluminum halide complexed acrylonitrile complex only differs from the olefin—zinc chloride complexed acrylonitrile complex in degree rather than in kind—i.e., the former is an unstable charge transfer complex capable of spontaneous uncoupling of the diradical system followed by intermolecular diradical coupling, while the latter is a stable charge transfer complex requiring radical attack to uncouple the diradical system. 

In later communications (27, 28) Hirooka reported that in addition to acrylonitrile, other conjugated monomers such as methyl acrylate and methyl methacrylate formed active complexes with organoaluminum halides, and the latter yielded high molecular weight 1 1 alternating copolymers with styrene and ethylene. However, an unconjugated monomer such as vinyl acetate failed to copolymerize with olefins by this technique. 

The dual function of the precatalysts 4 opened the way to well-controlled block polymerization of ethylene and MMA (eq. (5)) [89, 90]. Homopolymerization of ethylene (Mn = 10000) and subsequent copolymerization with MAA (Mn 20000) yielded the desired linear AB block copolymers. Mono and bis(alkyl/silyl)-substituted flyover metallocene hydride complexes of type 8 gave the first well-controlled block copoymerization of higher a-olefins with polar monomers such as MMA or CL [91]. In contast to the rapid formation of polyethylene [92], the polymerization of 1-pentene and 1-hexene proceeded rather slowly. For example, AB block copolymers featuring poly( 1-pentene) blocks (M 14000, PDI = 1.41) and polar PMMA blocks (M 34000, PDI = 1.77) were obtained. Due to the bis-initiating action of samarocene(II) complexes (Scheme 4), type 13-15 precatalysts are capable of producing ABA block copolymers of type poly(MMA-co-ethylene-co-MMA), poly(CL-co-ethylene-co-CL), and poly(DTC-co-ethylene-co-DTC DTC = 2,2-dimethyltrimethylene carbonate) [90]. 

Tertiary amine-functionalized olefins are not difficult to polymerize and copolymerize with group IV catalysts, provided that sufficient steric hindrance is present around the nitrogen atom. Amines of sufficient bulkiness, including diisopropyl and diphenyl derivatives, can be polymerized without the necessity of protection by Lewis-acid complexation. Smaller monomers (such as dimethyl and diethylamines) can be polymerized if 1 equiv of a proper alkylaluminum protecting group is used (vide infra). However, if the amine functionality is too near to the double bond, the additional steric bulk provided by the aluminum species may actually inhibit monomer coordination and polymerization. 

The high oxophilicity of early transition metal catalysts (titanium, zirconium, or chromium) causes them to be poisoned by most functionalized olefins, particularly the commercially available polar comonomers. However, there are examples of copolymerizations with special substrates or with very high levels of a Lewis acid incorporated into the polymerization system to protect the polar functionality through complexation. " Alternative routes to polar copolymers involving metathesis of cyclic olefins and functionalization of the resulting unsaturated polymer or metathesis of polar cycloolefins followed by hydrogenation to remove the resulting unsaturation have been published.The cost of these multistep... 

Another important issue in olefin polymerization is copolymerization of different types of monomers. If one can freely produce copolymers of non-polar and polar monomers, which are difficult to copolymerize with conventional initiators, it would provide useful polymer materials. The Ziegler type catalysts using trialkylaluminum is not suitable for polymerizing polar monomers, whereas late transition metal catalysts are more tolerant of polar monomers. Recently catalysts using late transition metal catalysts have been intensively studied [89]. Because of the obvious importance of these polymeric materials in industrial use, further studies are expected on the applicability of late transition metal complexes for polymerization. 

In addition, the salicylaldehyde derivative 5 has been reacted with 1,2-diaminoethane to divinylsalenes which were afterwards copolymerized with styrene to cross-linked polymers in which Co(II) was introduced [21]. Also divinyl-substituted Mn(II salen complexes have been successfully copolymerized [22,23]. The aim of this interesting research is the synthesis of heterogeneous catalysts for the asymmetric epoxidation of olefins using chiral Mn(III)-salen complexes [24]. 

Influences due to steric hindrance are mostly swamped by those due to polarity and resonance stabilization. For example, 1,2-disubstituted ethylene monomers form random copolymers with comonomers of similar polarity, i.e., dimethyl fumarate/vinyl chloride. If the polarities differ greatly, even alternating copolymers can be formed because of the formation of CT complexes, as, for example, with maleic anhydride/styrene (see also Section 22.3). Even two 1,2-disubstituted monomers copolymerize with each other if the polarities differ very greatly, as happens with, for example, maleic anhydride and stilbene, since the polar interaction in the transition state helps to overcome the steric hindrance. Threefold substituted olefins produce an additional stabilization without steric hindrance in the transition state, and so can be easily copolymerized with comomoners of opposite polarity. 

A few spontaneous copolymerizations between exceptionally reactive donor acceptor olefinic pairs have been observed. Miller and Gilbert [37] observed that vinylidene cyanide spontaneously copolymerized with vinyl ethers when the two monomers were mixed at room temperature. Yang and Gaoni [38] observed that 2,4,6-trinitrostyrene as the acceptor monomer spontaneously copolymerized with 4-vinylpyridine as the donor monomer when the two were mixed at room temperature. Butler and Sharpe [39] reported that divinyl ether and divinyl sulfone spontaneously copolymerized upon monomer mixing. Thus, the participation of the charge-transfer complex in the copolymerization mechanism of such strong electron donor electron acceptor monomer pairs appears to have considerable support. 

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