Ring-opening metathesis polymerization alkyne

Fig. 4.24. Another variation of the alkyne metathesis reaction alkyne ring-opening metathesis polymerization (alkyne ROMP).

The polymerization of the alkyne triple bond (Secs. 5-7d and 8-6c) and ring-opening metathesis polymerization of a cycloalkene (Secs. 7-8 and 8-6a) yield polymers containing double bonds in the polymer chain. Cis-trans isomerism is possible analogous to the 1,4-polymer-ization of 1,3-dienes. 

Introduction to Ring-Opening Metathesis Polymerization (ROMP) and 1-Alkyne Polymerization... 

Mechanistic studies revealed that alkyne metathesis and ring-opening metathesis polymerization of cycloalkynes proceed via metal carbyne complexes,217 218 which is also supported by theoretical studies.219 The polymerization of PhC=CMe with NbCIs or TaCIs yields a polymer that degrades to oligomers as a result of secondary metathesis reaction. A stable polymer, however, may be synthesized with TaCIs and Ph4Sn as a cocatalyst.220... 

SCHEME 1. Types of alkene and alkyne metathesis reactions. DBC, double bond cleavage TBC, triple bond cleavage ADMET, acyclic diene metathesis RCM ring-closing metathesis ROMP ring-opening metathesis polymerization... 

Reactivity characteristic of alkylidene complexes of tantalum is that the a-carbon is susceptible to electrophilic attack, in contrast to the electron-deficient a-carbon of Fischer-type carbene complexes of group 6 transition metals [62]. Based on this unique property of the alkylidene metal-carbon double bond, a range of new types of reactions has been developed. The discovery of the alkylidene complexes of tantalum was a key to understanding the mechanism of olefin metathesis, and they continue to play important roles in C—H bond activation, alkyne polymerization, and ring-opening metathesis polymerization. 

Figure 10-17 Ring-opening metathesis polymerization (ROMP) [111, 112]. represents a cyclic olefin or an alkyne. Any of the steps may be reversible, depending in part on the relative stabilities of the metallacycle and metallacarbene, and on the ring-strain of the ring in the monomer which is opened.

Ring-opening metathesis polymerization of cyclic alkynes... 

This chapter is arranged by the well-recognized types of olefin metathesis reactions, that is, ring-opening metathesis polymerization (ROMP), acyclic diene metathesis (ADMET) polymerization, ring-closing metathesis (RCM), and crossmetathesis (CM) (Fig. 12.1). Examples of alkyne metathesis are also included. 

Abstract Several routes to access ruthenium (Ru)-vinylidene complexes are described, the majority of which employ alkynes and a Ru source as the starting materials. The successful application of Ru-vinylidenes as efficient pre-catalysts for the synthesis of carbocyclic and heterocyclic compoimds by ring-closing metathesis (RCM) of a, -dienes, and in the synthesis of polymers by ring-opening metathesis polymerization (ROMP) of cyclooctene, norbomene, 5-substituted norbomene, and dicyclopentadiene is fully illustrated. Relevant aspects concerning the activity and selectivity of this type of Ru complexes in metathesis reactions are highlighted. 

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