Acyclic diynes, metathesis polymerization

The acyclic diyne metathesis polymerization of dodeca-2,10-diyne is catalysed by W(=CEt)(OCMe3)3 see equation 73. But-2-yne is eliminated and the product is an off-white insoluble powder with the same Tm as the polymer prepared from cyclooctyne (Section XII.B)7. 

An alternative method to make PAEs is the acyclic diyne metathesis (ADIMET) shown in Scheme 2. It is the reaction of a dipropynylarene with Mo(CO)6 and 4-chlorophenol or a similarly acidic phenol. The reaction is performed at elevated temperatures (130-150 °C) and works well for almost any hydrocarbon monomer. The reaction mixture probably forms a Schrock-type molybdenum carbyne intermediate as the active catalyst. Table 5 shows PAEs that have been prepared utilizing ADIMET with these in situ catalysts . Functional groups (with the exception of double bonds) are not well tolerated, but dialkyl PPEs are obtained with a high degree of polymerization. The progress in this field has been documented in several reviews (Table 1, entries 2-4). Recently, a second generation of ADIMET catalyst has been developed that allows... 

Alkyne metathesis is generally restricted to internal alkynes, and is driven to completion by the evolution of gaseous 2-butyne. Representative examples of alkyne cross-metathesis are depicted in Scheme 33, and include (i) dimerization of alkynylbenzoic acid derivative 287, (ii) alkyne cross-metathesis of 289 and bis(trimethylsilyl)acetylene, (iii) cross-metathesis of enyne 291 and various alkynes and metathesis dimerization of 291, and (iv) formation of high molecular weight alkyne-containing polymers through acyclic diyne metathesis (ADIMET) polymerization of acyclic diynes (e.g., 293) " using the molybdenum hexacarbonyl/2-chlorophe-nol system. 

Scheme 33 Representative examples of alkyne cross-metathesis and acyclic diyne metathesis (ADIMET) polymerization.

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