Carbenes polymerization catalysts derived from

Polymerization of acetylenes by metathesis-type catalysts such as M0CI5 and WCle/PluSn was first observed in the 1970s (Woon 1974 Masuda 1974, 1976), but the nature of the chain carrier was then in some doubt. However, it was soon found (i) that metal carbene complexes would initiate the polymerization of MesCC=CH at 60°C (Katz 1980a) (ii) that end-groups derived from such initiators could be detected in polymers of PhC=CH (Kunzler 1988b) and (iii) that triblock copolymers could be made by successive addition of norbomene, acetylene and norbomene to such initiators (Schlund 1989). All types of acetylene can be polymerized in this way and the reactions proceed by a ROMP-type mechanism see Ch. 10. 

ROMP and ROM are the two most frequently used methods in aqueous media. It was shown that the activity of the Ru catalyst is increased in the presence of small amount of water in the ROMP of 7-oxanorbornene derivatives. The most effective precursor was the aqua complex [Ru(H20)6](tos)2. After the polymerization was completed the aqueous catalyst phase could be reused and the catalytic activity increased in the subsequent reaction (Figure 26). An aqua-ruthenium (ii) olefin complex was isolated with higher catalytic activity than the adduct formed from the [Ru(H20)6](tos)2-complex and the 7-oxanorbornene derivative it was suggested that the Ru-carbene complex was formed from this compound. 

By adsorbing the perylene derivative tetraazaperopy-rene (TAPP) on Cu(lll) and annealing at 150°C, a Cu-coordinated porous network develops. Annealing at even higher temperatures (250 °C) results in the formation of ID chains—most probably with the Cu substrate acting as a catalyst—which consist of covalently coupled TAPP monomers (Figure 10). The reaction is supposed to proceed via a carbene intermediate. The first example shows that a reaction, which is well known from solution chemistry, can be adopted for the construction of polymeric struc-tnres on surfaces. In contrast, the second example demonstrates that on-surface reactions can allow for the formation of polymers which cannot be obtained via solution-based chemistry at all. 

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