1.4- Diethynylbenzene complex

The palladium-calalyzed polycondensation of 1,4-diethynylbenzene complex with 3-alkyl-2,5,-dibromothiophenes (scheme 23) was recently reported. These polymers displayed number-average molecular weights ranging from 13,000 to 24,400, with PDI ranging from 3.2 to 3.6. These organometallic polymers 80 exhibited a red shift of approximately 50 nm, indicating the n-delocalization in the backbone. The undoped polymer displayed semiconductor properties with a conductivity of 8.1 Xl0 S/cm. 

Metathesis of W2(OBu )e with one C=C triple bond of substituted 1,4-diethynylbenzenes has given carbyne complexes which can be converted into trans-WCl(=CC6H4C=CH)(dmpe)2. Functionalization via the W—Cl and =CH groups affords metalladiynes such as frans-W C=C(tol) (=CC6H4C=CSiPr 3)... 

Well-controlled polymerization of substituted acetylenes was also reported. A tetracoordinate organorhodium complex induces the stereospecific living polymerization of phenylacetylene.600 The polymerization proceeds via a 2-1 -insertion mechanism to provide stereoregular poly(phenylacetylene) with m-transoidal backbone structure. Rh complexes were also used in the same process in supercritical C02601 and in the polymerization of terminal alkyl- and arylacetylenes.602 Single-component transition-metal catalysts based on Ni acetylides603 and Pd acet-ylides604 were used in the polymerization of p-diethynylbenzene. 

Diethynylbenzenes 126 react with two equivalents of 2-((trimethylsilyl)ethynyl)benzene-l,4-diol 127 via an alkyne-zipper type bicyclization to afford the complex indenopyran ring systems 128 (Equation 60) <1998TL8237>. 

The polymer whose backbone is composed of platinum and alternately arranged butadiynyl and phenylenediethynylene groups, Pt-D1-Pt-D2 has been prepared by condensation of binuclear complex (38 a) with p-diethynylbenzene according to Eq. 22. Similarly, polymers, Pt-D -Pt-D1-Pt-D2 and Pt-D -Pt-D3, have been synthesized as described in Eqs. 23 and 2442). 

More recently, Au(I)-catalyzed ring-closure reactions of 1,2-diethynylbenzenes 158-160 bearing a terminal acetylene unit afford benzofulvene and dibenzopen-talene derivatives 161-163, as illustrated in Scheme 6.37 [79]. Gold vinylidene complexes are postulated to generate the respective reaction intermediates. These reactions are of importance for the construction of asymmetric polycyclic systems. 

It appears that the addition of ethynes to the carbonyl group in quinones is more efficient than the corresponding ethene process because irradiation of BQ or NQ in the presence of the eneyne 65 preferentially yields quinone methides. The photoaddition of l,4-bis(phenylethynyl)benzene to BQ in dichlo-romethane solution gives the quinone methide 66. However, the expected cyclobutene formation between duroquinone and 1,4-diethynylbenzene is somewhat more complex and affords not only 67, but also the ring-opened isomer 68 as well as the 2 1 adducts 69 and 70 in yields of 17,19,15, and 30%, respectively. ... 

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