Abstract
The acyclic organic alkynes and carbyne bonds exhibit linear shapes. Metallabenzynes and metallapentalynes are six- or five-membered metallacycles containing carbynes, whose carbine-carbon bond angles are less than 180°. Such distortion results in considerable ring strain, resulting in the unprecedented reactivity compared with acyclic carbynes. Meanwhile, the aromaticity of these metallacycles would stabilize the ring system. The fascinating combination of ring strain and aromaticity would lead to interesting reactivities. This mini review summarized recent findings on the reactivity of the metal–carbon triple bonds and the aromatic ring system. In the case of metallabenzynes, aromaticity would prevail over ring strain. The reactions are similar to those of organic aromatics, especially in electrophilic reactions. Meanwhile, fragmentation of metallacarbynes might be observed via migratory insertion if the aromaticity of metallacarbynes is strongly affected. In the case of metallapentalynes, the extremely small bond angle would result in high reactivity of the carbyne moiety, which would undergo typical reactions for organic alkynes, including interaction with coinage metal complexes, electrophilic reactions, nucleophilic reactions and cycloaddition reactions, whereas the strong aromaticity ensured the integrity of the bicyclic framework of metallapentalynes throughout all reported reaction conditions.
Highlights
The alkyne, which is a fundamental functional group in organic chemistry, is involved in a large number of reactions in organic chemistry [1,2,3,4,5]
Part of the reactivities of carbynes paralleled that of their organic parents, such as nucleophilic reactions, electrophilic reactions, photochemistry, oxidation and reduction, reactions with chalcogenides, reactions with unsaturated organic substrates and substitution on the α carbon (Figure 1)
Many efforts have been devoted to the chemistry bond angles around the acetylenic carbons are 180°
Summary
The alkyne (carbon-carbon triple bond), which is a fundamental functional group in organic chemistry, is involved in a large number of reactions in organic chemistry [1,2,3,4,5]. I.e., transition metal complexes with metal-carbon triple bonds, can be described as analogs of alkynes, whereas a transition metal replaces one of the sp carbons They have attracted considerable attention because of their remarkable features and their significance as catalysts or reagents for various types of organic transformations [5,6,7,8,9,10,11]. Ring strainThe would be moiety raised from the introduction oftoalkyne into an of organic cycle.carbon. Thereactivity incorporation of a metal center intodue the acetylenic carbon high ring [12,13].tension. The incorporation a metal center the acetylenic carbon would stabilize caused bytension the high. Metal center thecarbynes acetylenic carbon would stabilize thering strained cyclic carbon cycles containing.
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