Carbyne complexes catalysis

Iridium-carbon multiple bonds allenylidene complexes, 7, 355 carbene complexes, 7, 344 carbyne complexes, 7, 361 higher cumulenylidene complexes, 7, 358 vinylidene complexes, 7, 352 Iridium-carbon single-bonded complexes alkenyl complexes, 7, 319 alkyl and aryl complexes, 7, 303 in C-C bond-forming catalysis, 7, 335 characteristics, 7, 303... 

Complexes of nucleophilic carbenes are expected to react, like ylids, with electrophiles whereas complexes of electrophilic carbenes are expected to react, like carbocations, with nucleophiles and bases. All the complexes of terminal carbenes have in common the reactions with olefins, although their nature also varies. The principles of these reactions are detailed here, and application in catalysis and organic synthesis, are exposed in Parts IV and V respectively. Reactions of metal-carbene complexes leading to metal-carbyne complexes are mentioned in section 2. 

The three types of reactions of metal-carbyne complexes are metathesis whose catalysis aspects are developed in Chap. 15.2, the reactions of the carbynic carbon with electrophiles and nucleophiles depending on the polarity, and the heterocycle formations with the following substrates ... 

Metal-carbene and carbyne complexes occupy a central place in synthesis and catalysis. Metal-carbene or alkylidene eomplexes can have an eleetrophilic singlet carbene (Pettit type) or a nucleophilic triplet carbene (Sehrock type, often d ). 

The surface organometalhc complexes are thermally much more stable than their molecular counterpart. The example of [(=Si-0) WMes] on silica which is stable up to lOO C is a good example of the ability of a surface to stabilize a molecular compound which is explosive at room temperature So reactions can be performed on organometaUic compounds at very high temperature which is not possible in classical homogeneous catalysis. Such stability allows the observation of carbynes, carbenes, alkyls, amido, imido, and hydrides even at elevated temperatures. 

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