The stable cationic iridacyclopentenylidene [TpMe2Ir(=CHC(Me)=C(Me)CH2(NCMe)]PF6(A;TpMe2=hydrotris (3,5dimethylpyrazolyl)borate) has been obtained by α-hydride abstraction from the iridacyclopent-2-ene [TpMe2Ir(CH2C(Me)=C(Me)CH2)(NCMe)]. Complex A exhibits Brønsted–Lowry acidity at the Ir-CH2 and proximal (relative to Ir-CH2) methyl sites. The coordination of an extra molecule of acetonitrile to the iridium center initiates the reversible isomerization of the chelating carbon chain of A to the monodentate butadienyl ligand of complex [TpMe2Ir(CH=C(Me)C(Me)=CH2)(NCMe)2]PF6, which is capable to engage in a water-promoted C-C coupling with the MeCN co-ligands. The product is an aesthetically appealing bicyclic structure that resembles the hydrocarbon barrelene.