Polymerization phenylboration

Figure 9 The -77-conjugated organoboron polymer (9) produced by haloboration-phenylboration polymerization between 2,7-diethynylflourene and Ph2BBr. (Adapted from ref. 29.)...

Conjugated organoboron polymers were prepared by haloboration-phenylboration polymerization between diyne monomers and bromodiphenylborane (scheme 29).54 The polymerization was carried out by adding a slight excess of bromodiphenylborane to a tetrachloroethane solution of diynes at room temperature... 

The polymers prepared by phenylboration polymerization of diynes exhibit relatively high stability against air and thermal oxidation (scheme 30).55... 

Perfluorinated phenylboranes and perfluorinated phenylborates are well-established activators in the metallocene-initiated polymerization of olefins. With the increasing commercial importance of metallocene technology for the polymerization of ethylene and the copolymerization of ethylene and 1-alkenes, perfluorinated phenylboranes and perfluorinated phenylborates became more readily accessible. As a consequence, a few studies on the influence of these highly fluorinated activators on Nd-catalysis are available in literature. 

As depicted in Scheme 4, the treatment of 1,4-diethynylbenzene with 2eq. of diphenylbromoborane (selective haloboration) and the subsequent reaction with leq. of tolylene-2,4-diisocyanate (phenylboration polymerization) gives the corresponding alternating copolymers. 

A comparative analysis of the borate salts as electron donors with DIBF shows that the number of alkyl groups per boron atom determines reactivity. Dialkyldi-phenylborates initiate polymerization much more rapidly than do alkyltriarylbo-rates and are more stable in formulations. Therefore dialkyldiarylborates are likely to be preferred over the slower, less stable alkyltriarylborates. 

A wide range of novel polymers with boron in the backbone have been prepared by means of boration polymerizations (65,70-82). Diynes can be polymerized by hydroboration (70,71), phenylboration (65), and haloboration (72) to yield polymers (14),(15), and (16) (eq. 17). When an appropriate aromatic or heteroaromatic diyne is used, the resulting polymers have been shown to have extended 7T-conjugation through the vacant p-orbital of the boron atom (73,74). In fact, several have been shown to exhibit blue fluorescence emission. 

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