When bis(substituted cyclopentadienyl)- or bis(indenyl)zirconacyclopentadienes were treated with TiCl(4), a coupling reaction between the substituted cyclopentadienyl or indenyl ligand and the diene moiety proceeded to give indene or fluorene derivatives in moderate to high yields. With the sterically hindered t-Bu-substituted Cp ligand, the coupling products were obtained in high yields.

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Dimerization of aryl-substituted terminal alkynes on indenyl zirconium complexes occurred in a selective way. 1,4-Aryl-1,3-diene derivatives were formed exclusively after hydrolysis. It is in sharp contrast to the reaction on [Cp 2 Zr] complexes.Dimerization of aryl-substituted terminal alkynes 1 on low valent transition metal to metallacyclopentadienes is attractive since these metallacycles can be converted into various functionalized 1,3-dienes or substituted arenes.

Selective monohalogenation reaction of unsymmetrical zirconacyclopentadienes was developed by selective protonation and iodination reactions. Among the examined acids, acetic acid and acetylacetone showed the best yield and selectivity to afford the corresponding monoiododienes. For the zirconacyclopentadiene prepared from 3-hexyne and diphenylacetylene, the Et-bearing carbon–zirconium bond was selectively protonated with more than 90% selectivity.

Selective Protonation/Iodination of Unsymmetrical Zirconacyclopentadienes -[leading to mixtures of iododienes]. -(IGARASHI, E.; REN, S.; KANNO, K.-I.; TAKAHASHI*, T.; Chem. Lett. 39 (2010) 4, 350-351,