Electron-reservoir complexes and other redox-robust reagents: functions and applications

The functions and applications of electron-reservoir iron and cobalt sandwich complexes are reviewed with emphasis of the author's work using the 19-electron Fe-I complexes [(eta(5)-C5R5)Fe(eta(6)-C6Me6)], R = H or Me, the most electron-rich neutral molecules known to date and the 17-electron Fe-III complex [(eta(5)-C5Me5)Fe(eta(6)-C6Me6)][SbCl6](2), the strongest known organometallic oxidant. It is shown that the electron-reservoir concept involving steric protection of a central redox site and the resulting redox robustness allows to carry out a variety of functions such as references for the measurement of redox potentials, many useful stoichiometric and catalytic redox reactions, sensing of anions and cations and entry into the area of molecular electronics also including the nanoscale.