Polymerization of Functionalized Olefins

At the first step, the insertion of MMA to the lanthanide-alkyl bond gave the enolate complex. The Michael addition of MMA to the enolate complex via the 8-membered transition state results in stereoselective C-C bond formation, giving a new chelating enolate complex with two MMA units one of them is enolate and the other is coordinated to Sm via its carbonyl group. The successive insertion of MMA afforded a syndiotactic polymer. The activity of the polymerization increased with an increase in the ionic radius of the metal (Sm Y Yb Lu). Furthermore, these complexes become precursors for the block co-polymerization of ethylene with polar monomers such as MMA and lactones [215, 217]. 

The crystal structure of the 1 2 adduct 145 obtained by the reaction of [Cp SmH]2 with MMA was determined by X-ray analysis. One of the two monomer units is in the O-enolate form and the other unit coordinates to the samarium atom by the carbonyl group. A comparison between 145 and the 

7 Recent Trends in Polymerization Catalyzed by Organometallic Complexes of Transition Metals Other than Those of Group 4 

Similar isolobal and isoelectronic relationships [234, 235] have recently been observed for various organometallic complexes of both Group 5 metals 

Two other isoelectronic tantalum complexes, 156 [254] and 157 [255], have recently been reported to show a similar catalytic activity for the polymerization of ethylene (2 kg PE/h[Ta]mol and 12 kg PE/h[Ta]mol, respectively) when they were activated with MAO. 

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Of the cyclic olefins, norbornadiene replaces two CO groups from one Co to yield a labile complex 159, 160, 235), cyclooctatetraene replaces the axial CO ligands from all three cobalt atoms 53) and is itself replaced by other Lewis bases 330), and cyclopentadiene forms the unusual complex [95] with Co3(CO)gCMe 159,160). A few catalytic reactions were observed with methinyltricobalt enneacarbonyls including the dimerization of norbornadiene 160, 235) and the polymerization of functional olefins 312) with different Co3(CO)9CX. 

Single-site catalysts offer significant advantages over heterogeneous catalysts for the polymerization of functional olefins. One of the inherent liabilities of heterogeneous Ziegler—Natta catalysts is that they... 

The reaction is complicated in aprotic media by polymerization of the olefin at the electrode 132> apparently because anions such as 134 or 136 can initiate anionic polymerization of the activated olefin. Steric hindrance about the double bond can retard polymerization yields of hydrodimer from 132 in di-methylformamide as a function of the size of R are R = hydrogen or methyl, 0%, R % n-propyl, 25% R % i-propyl, 65% R % /-butyl, 95%, 32). Saturation of the double bond to produce, e.g., 136 from 132, is a side reaction in neutral... 

There are two principal ways to synthesize functional fluoropolymers (a) polymerization of functional fluoromonomers or copolymerization of fluoro-olefins with functional monomers, and (b) modification of common... 

As mentioned, polymer hybrids based on POs are effective as a compati-bilizer between the olefinic materials and polar ones. Furthermore, some polymer hybrids, such as PP-g-PMMA, etc., show good mechanical strength as polymer materials. On the other hand, surface modification of the molded polymer is one of the most attractive methods to let polyolefin materials functionalize. In this sense, surface polymerization of functional monomers on polyolefins is an important subject for polyolefin hybrids. As previously referred to, the growth of PS on PP via the RAFT process has been reported [92]. 

The Ru(II) catalysts currently used for olefin hydroarylation reactions are limited in terms of incorporation of substituents into the olefin substrate. For example, attempted hydrophenylation of isobutylene with TpRu(CO)(NCMe)(Ph) as catalyst does not yield new organic products. In addition, extension of catalysis to hetero-functionalized olefins using the TpRu(CO)(NCMe)(aryl) systems has not been successful. For electron-deficient olefins (e.g. styrene, methyl methacrylate, acrylonitrile) the TpRu(II) complexes initiate radical polymerization of the olefin in transformations that probably involve a Ru(III/II) redox change [4]. The... 

The developments over the past few years in the understanding of organometallic mechanisms and structure has led to a new generation of catalysts for the polymerization of cyclic olefins by the ring opening metathesis mechanism. These catalysts provide the means to control molecular weight and molecular weight distribution and to introduce functionality into polyolefins. 

Well-controlled block co-polymerization of 1-olefins with MMA or -caprolactone using the unique dual catalytic function of organolanthanide complexes which are active toward polymerization reactions of polar and non-polar monomers has been achieved with bridged [Me2Si(CsR4)2]LnFI (Ln = Y, Sm) type complexes. These initiators are highly active in co-polymerization processes without the presence of any co-catalyst (Scheme 271).985... 

The essential characteristic of Ziegler-Natta catalysis is the polymerization of an olefin or diene, using a combination of a transition metal compound and a base metal alkyl cocatalyst, normally an aluminum alkyl. The function of the cocatalyst is to alkylate the transition metal, generating a transition metal-carbon... 

This has two detrimental effects on polymerization. First, chelation strengthens the metal-olefin interaction, thereby raising the barrier for the insertion step. Second, it forces insertion through the endo face, in sharp contrast to the known propensity for norbornene to insert into metal-carbon bonds through the less hindered exo face [3 a, 5]. Consistent with this hypothesis has been our observation of the preferential uptake of the exo isomer in the polymerization of functional norbornene derivatives by Pd(PRj)(Me). For example. Fig. 9.3 shows the uptake profile versus time for the polymerization of 5-norbornene-2-carboxyhc acid ethyl ester starting with a monomer isomer ratio of 22% exo to 78% endo. Indeed, under certain conditions a polymer can be obtained from the exo isomer but not the endo isomer [10]. 

Another remarkable character of this class of Ni complexes is their tendency to promote living polymerization of a-olefins at low temperatures and with low concentrations of the monomer. Thus, the low-temperature polymerization of propylene leads to a material whose number average molecular weight (Mn) increases almost linearly as a function of time and propylene consumption, reaching values of M = 160 000 Daltons and polydispersities of ca. 1.13. This character allows these Ni catalysts to produce A-B-A type block copolymers composed of semicrystalline and amorphous segments, which is used to prepare thermoplastic elastomeric polymers. The Ni catalysts can also polymerize internal cyclic... 

The area of ethylene polymerization with late metal catalysts was rejuvenated when Brookhart and his group reported a family of new cationic Pd (II) and Ni(II) a-diimine catalysts (trademarked the Versipol catalyst system by DuPont) for the polymerization of ethylene, a-olefins, and cyclic olefins and the copolymerization of nonpolar olefins with a variety of functionalized olefins. These catalysts are now the focus of a joint development effort between the University of North Carolina at Chapel Hill and DuPont, and as can be seen from the scope of this review, they are being pursued at many other companies and universities. 

The ring-opening metathesis polymerization (ROMP) of functionalized olefins can be catalyzed by ruthenium aquo complexes and proceeds best in aqueous solution (Scheme 22). The formation of olefin complexes [Ru(H20)5(olefin)] ... 

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