Norbornadiene polymerization

Novel chiral. separations using enzymes and chiral surfactants as carriers have been realized using facilitated transport membranes. Japanese workers have reported the synthesis of a novel norbornadiene polymeric membrane with optically active pendent groups that show enantio.selectivity, which has shown promi.se in the. separation of propronalol. 

Copolymerization to form polyketones proceeds by the carbonylation of some alkenes in the absence of nucleophiles. Copolymerization of CO and norbornadiene takes place to give the polyketone 28(28]. Reaction of ethylene and other alkenes with CO affords the polyketones 29. The use of cationic Pd catalysts and bipyridyl or 1,10-phenanthroline is important for the polymerization [29-31]. 

A detailed study of ROMP of disubstituted norbornadienes (e.g., 2,3-dicarbo-methoxynorbornadiene or 2,3-bis(trifluoromethyl)norbornadiene (NBDF6) [124] showed that they are polymerized by Mo(f-butoxide) initiators in a well-behaved living manner to give essentially monodisperse homopolymers that are... 

For olefins, cyclic, or better hi- or tricyclic ring structures with large ring strain (norborn-2-enes or norbornadienes for instance) are required. Alternatively, 1-alkynes can be used. In this case, the term 1-alkyne polymerization applies. This reaction proceeds via a- or j6-insertion of the alkyne into the metal-carbon double bond (Scheme 1). Both insertion mechanisms lead to a conjugated polymer. With a few exceptions [1-3], polymerizations based on a-insertion are the preferred ones, since they offer better control over molecular weights due to favorable values of kj/kp (ki, kp = rate constants of initiation and propagation, respectively). 

Scheme 1 ROMP of a 2,3-disubstituted norbornadiene, a 2-substituted norborn-5-ene and polymerization of a 1-alkyne via a- and /3-addition, respectively. A and B are initiator-and termination-derived endgroups, respectively...

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. 

The monomers dealt with can be polymerized by various mechanisms, not only by ROMP. For example, a rapid polymerization of norbornadiene occurs using a homogeneous catalytic system consisting of nickel acetylacetonate or a nickel-phosphine complex, such as nickel bis-(tri-n-butylphosphine) dichloride (NiCl2(TBP)2) or nickel bis-(tricyclohexylphosphine) dichloride (NiCl2(TBP)2). Nickel acetylacetonate as catalyst is known to initiate rather a classical vinyl polymerization (7). The classical vinyl polymerization... 

Two series of cationic complexes, [Mo(NO)2L4]2+ (L = RCN, py, etc.) and [MoCl(NO)2L3]+ have been prepared by halide abstraction from [MoCl2(NO)2L2] using silver salts in DME (method D). Some members of the series catalyze the polymerization of norbornadiene, whereas the uncharged parent compounds do not.29 The series [Mo(NO)2L4]2+ (L is a displaceable solvent such as THF) may also be obtained by treatment of [Mo(CO)6] with NO[PF6] followed by addition of further ligands such as bipy.29 This latter reaction also gives [ Mo(NO)2(PF6)2 ] which is assumed to be a polymer with weak PF6 bridges.29... 

The carbonylation of norbornadiene in benzene solution catalyzed by PdCl2 leads to the formation of a polymeric ketone.532 This unusual reaction is believed to have the complex [PdCl2(nbd)] as its catalyst precursor, and the mechanism proposed for it is given in Scheme 47. 

However, the fact that complexes in which R = Ph, F, M02CH, and C2F6 also initiate polymerization of acrylonitrile suggests that chemistry at cobalt may be involved instead. The displacement of carbon monoxide ligands by diolefins to give stable complexes of type RCCo3(CO)7(nor-bornadiene) in the case of norbornadiene has been reported (18, 76), so that such a process is entirely possible. 

Some promise is offered by the application of PCMU to power conversion devices [137], Thus polymeric cobalt-containing porphyrins can be used for photochemical power storage in a norbornadiene-quadricyclane system [138]. 

The complex Mo(tfd)3 was reported by King and co-workers (86) to catalyze the conversion of quadricyclane to norbornadiene (Eq. 9), polymerization of quadricyclane or norbornadiene, as well as the addition of water to quadricyclane to give nortricyclanol (Eq. 15). The reactions appear to involve pseudo-[4 + 2] cycloaddition to the sulfur atoms in the dithioketone form of the metal... 

Chiral polymers have been applied in many areas of research, including chiral separation of organic molecules, asymmetric induction in organic synthesis, and wave guiding in non-linear optics [ 146,147]. Two distinct classes of polymers represent these optically active materials those with induced chirality based on the catalyst and polymerization mechanism and those produced from chiral monomers. Achiral monomers like propylene have been polymerized stereoselectively using chiral initiators or catalysts yielding isotactic, helical polymers [148-150]. On the other hand, polymerization of chiral monomers such as diepoxides, dimethacrylates, diisocyanides, and vinyl ethers yields chiral polymers by incorporation of chirality into the main chain of the polymer or as a pedant side group [151-155]. A number of chiral metathesis catalysts have been made, and they have proven useful in asymmetric ROM as well as in stereospecific polymerization of norbornene and norbornadiene [ 156-159]. This section of the review will focus on the ADMET polymerization of chiral monomers as a method of chiral polymer synthesis. 

These properties have already been used to synthesize a wide variety of stereoregular norborn-2-ene- and norbornadiene-based polymers [22,54,55, 126,129]. Adding a base such as quinuclidine has a strong impact on these polymerizations. Although the base is not believed to coordinate to molybdenum... 

Ethylene has been co-polymerized with a range of cycloolefms, including cyclobutene,596 cyclopentene,596 cyclohexene,597 norbornene (NB),596 5-phenyl-2-norbornene,598 5-vinyl-2-norbornene,599 5-ethylidene-2-norbornene,600 dimethano-octa-hydro-naphthalene,601 phenyldimethano-octahydro-naphthalene,598 and norbornadiene.602 Several non-conjugated cyclodiolefins have been co-polymerized as well.603... 

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