CHEMICAL AND BIOLOGICAL SCIENCES CHEMICAL AND BIOLOGICAL SCIENCES
 |
L. Keith Woo Associate, Ames Laboratory 3759 Gilman Hall |
PERSONAL HISTORY
RESEARCH INTERESTS
The research in my group spans an extensive spectrum of chemistry, ranging from organic synthesis of complex ligand systems to physical studies on the kinetics and thermodynamics of new reactions. In addition, we are interested in the synthesis and reactivity of novel coordination compounds and organometallic complexes. Our research is directed towards understanding fundamental transition metal behavior and reactivity in both biological systems and in new materials. Aspects of our current efforts are summarized below.
Coordination Chemistry. We have recently developed new methods for preparing transition metal and main group porphyrin complexes containing metal-ligand multiple bonds and other novel features. Our discoveries have greatly increased the realm of porphyrin chemistry and continue to be an active area of exploration.
Catalysis. Through our evolving work in organometallic chemistry, we have demonstrated that osmium and iron porphyrin complexes efficiently catalyze the cyclopropanation of olefins in the presence of diazo reagents. Our catalysts produce some of the highest known stereoselectivities for styrene cyclopropanation. Our research provides strong evidence that the mechanism of this process involves a carbene complex. In fact, we have isolated and structurally characterized several osmium carbene complexes. We are pursuing mechanistic studies and attempting to design enantioselective catalytic systems. This includes the use of C2- and C4-symmetric porphyrin and chiral tetraazaannulene ligands.
We have recently discovered that iron(II) porphyrin complexes are extremely efficient catalysts for the olefination of carbonyl compounds with diazo reaagents. These catalysts are among the most effective and inexpensive known to date.
In our most recent finding, titanium(IV) oxo porphyrins catalytically cleave 1,2-diols to the corresponding carbonyl compounds. The net reaction consumes a half an equivalent of dioxygen and liberates water. Kinetic and mechanistic studies on this reaction are underway.
RECENT PUBLICATIONS
"Alcohol Oxidation with Dioxygen Mediated by Oxotitanium Porphyrin and Related Transition Metal Complexes." Du, G.; Mirafzal, G. A.; Woo, L. K. Journal of Porphyrins and Phthalocyanines, 2005, 9, 206-213.
"Reductive Coupling of Carbonyl Compounds with a Low-Valent Titanium(II) Porphyrin Complex." Du, G.; Mirafzal, G. A.; Woo, L. K. Organometallics 2004, 23, 4230-4235.
"Reaction of Tin Porphyrins with Vicinal Diols." Du, G.; Ellern, A.; Woo, L. K. Inorg. Chem. 2004, 43, 2379-2386.
"Iron Porphyrin-Catalyzed Olefination of Carbonyl Compounds with Ethyl Diazoacetate." Cheng, G.; Mirafzal, G. A.; Woo, L. K. Organometallics 2003, 22, 1468–1474.
"Synthesis, Characterization, and Reactivity of Group 4 Metalloporphyrin Diolate Complexes." Du, G.; Woo, L. K. Organometallics 2003, 22, 450-455.
"Synthesis and Characterization of Chiral Tetraaza Macrocyclic Nickel(II) and Palladium(II) Complexes." Du, G.; Ellern, A.; Woo, L. K. Inorg. Chem. 2003, 42, 873-877.
"Asymmetric Cyclopropanation of Styrene Catalyzed by Chiral Macrocyclic Iron(II) Complexes." Du, G.; Andrioletti, B.; Rose, E.; Woo, L. K. Organometallics 2002, 21, 44904495.
"Novel Coordination in the First Tellurium Porphyrin Complex. Synthesis and Crystal Structure of [Te(TTP)Cl2]." Grubisha, D. S.; Guzei, I. A.; Al-Salim, N.; Boyd, P. D. W.; Brothers, P. J.; Woo, L. K. Angew. Chem., Intl. Ed. 2001, 40, 4743-4745.
"Mechanism of Cyclopropanation Reactions Mediated by (5,10,15,20-tetra-p-tolylporphyrinato)osmium(II) Complexes." Hamaker, C. G.; Djukic, J.-P.; Smith, D. A.; Woo, L. K. Organometallics 2001, 20, 5189-5199.
"Atom Transfer Reactions of (TTP)Ti(h2-3-Hexyne): Synthesis and Molecular Structure of trans-(TTP)Ti[OP(Oct)3]2." Thorman, J. L.; Young, V. G., Jr.; Boyd, P. D. W.; Woo, L. K. Inorg. Chem. 2001, 40, 499-506.
