C–H and C–C bonds activation by iridium clusters: Synthesis and solid state structure of [Ir6(CO)14(μ3-η1:η2:η1-C7H8)]

The reaction between norbornene (C7H10) and Ir6(CO)16 in refluxing toluene yields the substituted cluster [Ir6(CO)14(C7H8)]. In the solid state, the six iridium atoms define an octahedral metal cage, and one face is capped by the C7H8 ligand, coordinated through a 1,2-vinylidene unit. The loss of two hydrogen atoms from the olefin is, presumably, the result of a double oxidative addition of its C–H bonds, followed by elimination of a hydrogen molecule from the cluster. The bonding parameters of the organic fragment, as well as the architecture of the carbonyl ligands, closely match those found in the alkyne-substituted [Ir6(CO)14(PhCCPh)] complex.The cluster [Ir6(CO)14(C7H8)] was characterized through 1H-, 13C- and bidimensional COSY NMR.

Graphical abstractThe reaction between norbornene (C7H10) and Ir6(CO)16 in refluxing toluene yields the substituted cluster [Ir6(CO)14(C7H8)]. To be coordinated to the metal centers, the two vinylic carbon atoms lose two hydrogen atoms via a double oxidative addition of its C–H bonds, followed by elimination of a hydrogen molecule from the cluster. As a result, the C7H8 fragment is coordinated through a 1,2-vinylidene unit. In accordance, the bonding parameters of the Ir3C2 unit closely match those found in other alkyne-substituted complexes.Figure optionsDownload full-size imageDownload as PowerPoint slide