Seminar Series:
Prof. Harry B. GrayCalifornia Institute of Technology
Tuesday, November 1, 2016 - 11:00am
Chemistry, Room 400 ~ CMS Seminar

The dianionic oxo ligand occupies a very special place in coordination chemistry, owing to its ability to donate pi electrons to stabilize high oxidation states of metals. I submitted my first papers on the ligand field theory of multiple bonding in metal-oxos to Bob Parry, the founding editor of Inorganic Chemistry. He liked them, and they were published in 1962 in the first volume of the journal. The theory, which accounts for the optical and EPR spectroscopic properties of these complexes, also predicts that there must be an "oxo wall" between Fe-Ru-Os and Co-Rh-Ir in the periodic table. There have been many attempts to break down the wall, but it is still in pretty good shape! I will review this early work, then discuss the roles metal-oxos play in two of the most important chemical reactions on planet Earth, hydrocarbon oxygenation catalyzed by cytochrome P450, and solar-driven water oxidation catalyzed by the manganese-calcium cluster of photosystem-II. Water splitting catalyzed by inorganic materials also is of great current interest. In this area, recent work in my lab has shown that high-valent iron-oxos likely are key intermediates in water oxidation catalyzed by robust Fe,Ni-layered double hydroxides