Key Laboratory of Biopesticide and Chemical Biology (Ministry of Education), College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
Molecules. 2020 Oct 30;25(21):5050. doi: 10.3390/molecules25215050.
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.
无环有机炔烃和碳炔键呈现线性形状。金属苯炔和金属戊二炔是含有碳炔的六元或五元金属环，其碳炔键角小于 180°。这种扭曲导致了相当大的环应变，与无环碳炔相比，表现出前所未有的反应活性。同时，这些金属环的芳香性会稳定环体系。环应变和芳香性的迷人组合将导致有趣的反应性。这篇迷你综述总结了最近关于金属-碳三键和芳香环体系反应性的发现。在金属苯炔的情况下，芳香性将占主导地位，反应类似于有机芳烃，特别是在亲电反应中。同时，如果金属碳炔的芳香性受到强烈影响，可能会观察到金属碳炔的迁移插入的片段化。在金属戊二炔的情况下，极小的键角会导致碳炔部分的高反应性，其将经历典型的有机炔烃反应，包括与铸币金属配合物的相互作用、亲电反应、亲核反应和环加成反应，而强芳香性确保了金属戊二炔的双环骨架在所有报道的反应条件下的完整性。
