Titanium complexes cyclooctatetraene

Additional improvements in preparations of polyacetylene came from several developments. One is the use of metathesis polymerization of cyclooctatetraene, catalyzed by a titanium alkylidene complex. The product has improved conductivity, though it is still intractable and unstable. By attaching substituents it is possible to form soluble and more stable materials that can be deposited from solution on various substrates. Substitution, however, lowers the conductivity. This is attributed to steric factors introduced by the substituents that force the double bonds in the polymeric chains to twist out of coplanarity." Recently, a new family of substituted polyacetylenes was described. These polymers form from ethynylpyridines as well as from ethynyldipyridines. The polymerization reaction takes place spontaneously by a quatemization process ... 

The structure of [(CgHQ)Nd(OC HQ)2I rNd(CQHg)2] can be contrasted with the structure of Ti2(CgHQ)3.5S,se in the titanium structure, both titaniums are complexed by one [8]annulene, but they share a third cyclooctatetraene that has a twisted structure that is, the cyciooc-tatetraene acts as two diene units in coordinating to the two titaniums. 

Mixed 5-8 titanium complexes have been prepared by reduction of Cp TiCb and CpTiCb with Mg in THF in the presence of cyclooctatetraene to give Cp ( ) -C8H8)Ti... 

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