Reaction of Carbyne Complexes

Reactions of carbyne complexes that maintain the integrity of the metal-carbon triple bond form the third route to new carbynes. Substituent modification, ligand exchange, oxidation, and reduction reactions have all been reported (see, e.g., Ref. 126). 

The reactions of carbyne complexes will be discussed, albeit more briefly, along the lines developed for alkylidene complexes, to emphasize the parallels. Once again, as with alkylidenes, early generalizations suggested two classes of complexes, Fischer-type and Schrock-type, which have subsequently been recognized as extremes in a tunable reactivity continuum. Furthermore, within the chemistry of tungsten, Fischer-type... 

In several cases oxidation reactions of carbyne complexes were found to be accompanied by transformations of the carbyne ligands. Complex 63... 

Photochemically induced electron transfer reactions of carbyne complexes were also reported by McElwee-White and co-workers [Eq. (58)]... 

A general approach to metallacyclobutadienes (90) is the reaction of carbyne complexes with alkynes. These four-membered rings are intermediates in the metathesis of acetylenes. Compounds 90 (M = W) offer a possi-... 

Weiss, K. Catalytic reactions of carbyne complexes. Carbyne Complexes 1988, 205-228. 

Other Lewis acids react with metal carbynes. Although the initial attack often occurs at Ccaibyne, the final product may be the result of subsequent reactions that may be difficult to rationalize mechanistically.99 Some of the problems at the end of Chapter 10 will depict more of the chemistry of carbyne complexes. Perhaps the most significant reaction of carbyne complexes is n bond metathesis, which has been alluded to in the discussion on procedures for metal-carbyne synthesis. We will see more consideration of this reaction in Chapter 11. 

Many carbene complexes undergo nucleophilic attack at the carbene carbon. This chemistry is presented in more detail in Chapter 13 on metal-ligand multiple bonds. In brief, cationic carbene complexes tend to imdergo simple addition processes to generate neutral products (Equation 11.8), whereas neutral complexes can react by either addition (Equation 11.9) or by a sequence of addition and elimination reactions (Equation 11.10). Fischer has shown that the aminolysis of alkoxycarbene complexes occurs by initial attack at the carbene carbon by a mechanism similar to that for the aminolysis of organic esters. Although less studied than reactions of carbenes with nucleophiles, reactions of carbyne complexes with nucleophiles are also known, and these reactions generate carbene complexes. ... 

Weiss, K. (1988) Catalytic Reactions of Carbyne Complexes in H. Fischer, Transition Metal Carbyne Complexes, VCH Publisher Weinheim. 

ON THE ROUTE FROM STOICHIOMETRIC TO CATALYTIC REACTIONS OF CARBYNE COMPLEXES. Part XX (1)... 

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