Aromatic iridacycles.

The first example of a family of related aromatic metallacycles has been synthesized, and the physical and chemical properties of its individual members have been investigated. The metallacyclic rings in these compounds are, in general, constructed from pentadienyl- or heteropentadienyliridium precursors via C-H bond activation processes. The molecules display the structural and spectroscopic features of aromaticity, including ring planarity, pi-bond delocalization, and diamagnetic ring current effects. The reactivity profile of the molecules is complex, reflecting the simultaneous presence of an aromatic ring and a reactive metal center.