Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published October 17, 2011 | public
Journal Article

Noninnocence in Metal Complexes: A Dithiolene Dawn

Abstract

Noninnocence in inorganic chemistry traces its roots back half a century to work that was done on metal complexes containing unsaturated dithiolate ligands. In a flurry of activity in the early 1960s by three different research groups, homoleptic bis and tris complexes of these ligands, which came to be known as dithiolenes, were synthesized, and their structural, electrochemical, spectroscopic, and magnetic properties were investigated. The complexes were notable for facile one-electron transfers and intense colors in solution, and conventional oxidation-state descriptions could not account for their electronic structures. The bis complexes were, in general, found to be square-planar, including the first examples of this geometry for paramagnetic complexes and different formal dn configurations. Several of the neutral and monoanionic tris complexes were found to have trigonal-prismatic coordination, the first time that this geometry had been observed in molecular metal complexes. Electronic structural calculations employing extended Hückel and other semiempirical computational methods revealed extensive ligand–metal mixing in the frontier orbitals of these systems, including the observation of structures in which filled metal-based orbitals were more stable than ligand-based orbitals of the same type, suggesting that the one-electron changes upon oxidation or reduction were occurring on the ligand rather than on the metal center. A summary of this early work is followed with a brief section on the current interpretations of these systems based on more advanced spectroscopic and computational methods. The take home message is that the early work did indeed provide a solid foundation for what was to follow in investigations of metal complexes containing redox-active ligands.

Additional Information

© 2011 American Chemical Society. Received: May 31, 2011. Publication Date (Web): September 13, 2011. We dedicate this Forum contribution to the memory of our dear friend, Ed Stiefel, who made deep and lasting contributions to our story of dithiolene noninnocence. We are enormously grateful to the National Science Foundation for steadfast support of our work in the 1960s. We are still working with the NSF, now as PI (H.B.G.) and advisor (R.E.) in the CCI Solar Fuels Program (CHE-0802907).

Additional details

Created:
August 19, 2023
Modified:
October 24, 2023