Coordination polycondensation

Step growth reactions involving the homo- and heteropolycondensation of various bifunctional unsaturated monomers in the presence of transition metal-based coordination catalysts have appeared to be a very useful synthetic tool for the preparation of low and high molecular weight polymers with an unsaturation in the polymer backbone. These reactions lead to unsaturated hydrocarbon and non-hydrocarbon polymers where polymeric chains are formed by carbon-carbon and carbon-heteroatom coupling respectively. 

Essentially, two types of unsaturated bifunctional compound display the capability of being condensed in high yield, via a transition metal-catalysed carbon-carbon coupling reaction, into their requisite generic high molecular weight polymers plus a small molecule non-conjugated acyclic dialkenes and haloaromatic derivatives. 

Acyclic dienes undergo metathesis polycondensation (acyclic diene metathesis admet ) to poly(alkenylene)s in the presence of W, Mo and Ru alkylidene complexes as catalysts [1]  

A unique aspect of acyclic diene metathesis polycondensation is its ability to produce new polymer backbones by strategic monomer design [1]. 

Haloarene derivatives used for coordination polycondensation are primarily represented by halostyrenes and haloarylacetylenes which undergo selfcoupling to poly(arylene vinylene)s [scheme (2)] and poly(aryleneacetylene)s [scheme (3)] respectively, and by dihaloarenes which, mainly in a combination with alkenes or divinylarenes and acetylenes or diacetylenes, undergo crosscoupling to poly(arylene vinylene)s [schemes (4) and (5)] and poly(arylene acetylene)s [schemes (6) and (7)] respectively [2]  

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Catalysts for coordination polycondensation involving haloarene derivatives are usually based on Pd complexes, although Ni complexes can be employed in some instances. 

Also, the coordination polycondensation of dihaloarenes via reductive coupling with metals or metal complexes, catalysed by transition metal complexes, leads to polyarylenes [2,3] ... 

Indicate monomers and catalysts that will produce poly(l,4-phenylene vinylene) and poly(l,4-phenylene-l,6-hexenylene) via coordination polycondensation of various types. 

The C-C coupling reaction between RMgX and R X is considered to proceed though an Ni(R)(R )Lm intermediate, and acceleration of the reductive elimination of R-R by coordination with olefinic or aromatic R X to Ni(R)(R )Lm is necessitated for a smooth catalytic reaction [15,16]. On these bases Ni-pro-moted dehalogenative polycondensation of dihalo organic compounds is suited to the preparation of 7i-conjugated aromatic and olefinic polymers. 

The adduct formed by two lithium atoms with polycondensed aromatic hydrocarbons crystallizes with two solvating molecules of TMEDA. The structure of the crystals derived from naphthalene (73) and anthracene (74) was elucidated by XRD. This arrangement of the unsolvated lithium atoms, in 7 -coordination fashion on the opposite sides of two contiguous rings, was found by MNDO calculations to be the most favorable one for naphthalene, anthracene and phenanthrene (75) . 

Polycondensates with the Ligand as a Comonomer. Metal-bearing polycondensates in which the ligand moiety alone or in combination with the coordinated metal ions form one of the backbone comonomers are exemplified by the following polymers reported by Wudl et al [48], Biswas and Mazumdar [49, 50] and by Takahashi et al. [51] in the synthesis of organotin polymer by a similar condensate (Figs. 20, 21). 

Among the few examples of hybrid materials using the metal-oxygen core for their construction is the composite obtained from BuSn(OPri)J. The hydrolysis-polycondensation reactions are quite fast for the derivatives of tin (as the increase in the coordination number takes place), but the Sn-C bond is quite stable against the attacks of nucleophilic reagents like water. It makes possible the addition of the organic molecules to the oxopolymers — the tin-... 

Trivalent carbenium ions play a key role, not only in the acid-catalyzed polymerization of alkenes [Eq. (5.348)] but also in the polycondensation of arenes (7r-bonded monomers) as well as in the cationic polymerization of ethers, sulfides, and nitrogen compounds (nonbonded electron-pair donor monomers). On the other hand, penta-coordinated carbonium ions play the key role in the electrophilic reactions of cr-bonds (single bonds), including the oligocondensation of alkanes and alkenes (Section 5.1.5). 

One of the major problems in the chemistry of three-coordinated boron-nitrogen compounds is their relative instability towards hydrolysis 79>8°). This feature reduces their possible applications in many areas such as in the medicinal field or utilization for polycondensation-products. However, steric hindrance by bulky substituents on the borazine ring leads to compounds with enhanced hydrolytic stability, particularly when no solvent is present in which they may dissolve. This observation has resulted in extensive research on sterically hindered boron-nitrogen ring compounds. 

Coordination carbonylation polycondensation has been extended from the synthesis of polyamides [scheme (15)] and polyarylates [scheme (16)] to reactions using other nucleophilic monomers that, with dihaloarenes and carbon monoxide, yield poly(imide-amide)s, poly(acylhydrazide)s, and poly(benzoxa-zole)s [165,170,171],... 

A number of synthetic methods have been successfully developed for the synthesis of block copolymers. They include polycondensation, anionic, cationic, coordinative and free-radical polymerizations and also mechano-chemical synthesis. Despite the exceptional amount of attention paid to the prospects of various catalytic systems, radical polymerization has not lost any of its importance, particularly in this area. Its competitiveness with other methods of conducting polymerization are attributable to the simplicity of the mechanism and good reproducibility. Actually, the extensive use of free radical polymerization in practice is well understood when considering the ease of the process, the soft processable conditions of vacuum and temperature, the fact that reactants do not need to be highly pure and the absence of residual catalyst in the final product. Thus, it can be easily understood that more than 50% of all plastics have been produced industrially via radical polymerization. 

Recently, Shirai and Hojo25) have reported the synthesis of the soluble coordinate polymers containing metal-phthalocyanines in the main chain according to Scheme 2 (Eq. 7). The polymers obtained by polycondensation of metal-phthalocyanines bearing peripheral carboxy groups attached to various aromatics, -QH4-, -CsHr-CHz-CgH, exhibit higher conductivities (10-11 10-6 Q cm-1) than the corresponding monomer complexes. 

When starting from bifunctional bis(l,2-dioximes) in the reaction with metal ions, coordination polymers were prepared by polycondensation. 

The first linear polymers containing [2]catenanes in their backbones (mechanically linked main chain polymers, architecture A) were based on the Sauvage transition metal-coordinated catenanes. Polycondensation reactions were carried out between a diacid and a catenane diol to give a poly[2]catenane with Mn (600000) and Mw (4200000) based on polystyrene standards (Figure 4). 

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