Cyclopropanes carbene/carbyne complexes

Cyclopropyl-substituted transition-metal carbene and carbyne complexes, especially as cyclo-propylidene- or as cyclopropylcarbene complexes, have been used as synthetic building blocks with or without ring opening. Examples of cyclopropane synthesis via decomplexation are described in Section 1.A.5.2.6. 

IV.9 Cyclopropanation and Other Reactions of Palladium-Carbene (and Carbyne) Complexes... 

The discussed reactions of carbene and carbyne complexes show that they have essential significance as catalysts or unstable transient intermediate compounds in such catalytic processes as metathesis of olefins and other unsaturated compounds, Fischer-Tropsch synthesis, syntheses of cyclopropanes from diazoalkanes and olefins, and polymerization of olefins and alkynes as well as in organic synthesis. Except for alkynes [reaction (5.132) ] some compounds containing double bonds react with carbon monoxide and carbene ligands to form bonds with those groups. Examples of such compounds are enamines, ynamines, and Schiff bases. The JV-vinylpyrrolidone (enamine), methoxyphenylcarbene, and excess of CO (higher pressure) react to furnish enaminoketone. 

The carbyne carbon atoms in both [W(CO)2 HB(pz)3)(CSMe)] (449) (266) and [W(CMe)Cp(CO)2] (450) (267) are nucleophilic and react with protons and the methylthio cation, SMe , to form cationic carbene complexes. Whereas the first type of carbene complex is typically electrophilic (257), the latter one, 451, is nucleophilic, and treatment with trifluoroace-tic acid produces a cationic metallathia cyclopropane complex (452) (268). 

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