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Alkyne, alkene, and “allene”? A stable five-membered metallacycloalkyne 1 with alkylidene moieties was treated with an alkali metal to give a dianionic species 2, which was transformed into a 1-zirconacyclopent-3-ene complex by protonation. The alkylation of 2 afforded zirconocene–η4-1,3-enyne complexes 3, which can be regarded as formal “1-zirconacyclopenta-2,3-dienes”. Ar=4-EtC6H4; R=Me, Me3Sn.
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Suzuki et al. (2008) studied this question.
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