Pentadienyl ligands: Their properties, potential, and contributions to inorganic and organometallic chemistry

Pentadienyl ligands have been found to possess many unique and potentially useful characteristics, including the ability to adopt a wide variety of eta(1), eta(3), and eta(5) bonding modes, a propensity for bonding to metals in low oxidation states, a tendency toward forming sterically crowded complexes, and the ability to engage in a wide variety of coupling reactions, even while being more strongly bound to a metal center than the ubiquitous cyclopentadienyl Ligand. The combination of these properties has led to a rich body of chemistry for these ligands, and the promise that much more remains to be gained.