Member, Materials Science Institute

B.S., Purdue University, 1975. Ph.D., California Institute of Technology, 1979 (Harry Gray). Honors and Awards: Alfred P. Sloan Fellow, 1986-88. At Oregon since 1985.

Principal Research Interests:

The research in Tyler’s laboratory focuses on mechanistic organometallic and inorganic chemistry, polymer chemistry, catalysis, and photochemistry.

In one project, we are studying aqueous phase homogeneous catalysis. Our group is using its expertise in synthesis to modify organometallic catalysts so they are water-soluble. The reason for doing this is that water is an environmentally benign solvent, so there is a big push to convert many catalytic processes from organic solvents to water. One overall goal of our research is to investigate differences in the reaction mechanisms between water and organic solvents. In recent studies, we discovered active catalysts for nitrile hydration, olefin polymerization, olefin hydration, carbonylations, and assorted C-H bond activation reactions – all in aqueous solution

Proposed mechanism for the hydration of nitriles with Cp'₂Mo(OH)(OH₂)+

Another system under investigation is the reaction of nitrogen and hydrogen to form ammonia at low temperature using water-soluble organometallic and coordination complexes as catalysts in aqueous solution. This project has led to a number of surprises, particularly concerning the remarkable ability of H₂ to act as a ligand in aqueous solution. The scheme below shows a system we recently discovered that reacts H2 with N2 to form ammonia at room temperature and atmospheric pressure. Efforts are underway to improve the efficiency of this reaction and to understand the reaction mechanism.

 

X-ray crystal structure of the Fe(DMeOPrPE)2Cl2 complex.

Yet another project in the general area of aqueous organometallic chemistry is our synthesis of water-soluble phosphine complexes that reversibly bind dinitrogen. Dinitrogen is a major contaminant in natural gas and our research is aimed at finding complexes that bind dinitrogen at high pressure and release it at low pressure. The goal is to use these complexes as scrubbers for removing dinitrogen from natural gas, thus making available a sizable fraction of our country’s natural gas reserves for energy use. In a similar project with a related goal, we are studying catalytic methods for removing sulfur from petroleum. An especially innovative aspect of this desulfurization project is our use of microscale reactors to enhance the separation.

Another project underway in our laboratory is the synthesis and study of polymers that are photochemically degradable with visible light. It is noteworthy that photochemically degradable polymers have many potential uses in environmental applications, in medicine, and in materials science – but only if a way can be found to control the onset of photodegradation.

A photodegradable polyurethane

Our goal is to design polymers in which we can control the onset of photodegradation. Perhaps not surprisingly, there are a number of factors that control the onset and rate of polymer photodegradation, and our research is quantifying how each of these factors influences polymer photodegradation. Among the various factors that affect degradation, our work suggests that the “radical cage effect” is especially important in determining the rate of polymer decomposition. To probe the cage effect, we are doing femtosecond time-scale laser pump-probe studies on a variety of polymers and oligomers to investigate the relationship between the magnitude of the cage effect and the rate of photodecomposition. Our mechanistic investigations of the radical cage effect have led to many fundamental discoveries, such as an example of “in-cage” radical trapping by an agostic hydrogen interaction.

Selected Publications:

Reduction of N2 to Ammonia and Hydrazine Utilizing H2 as the Reductant. John D. Gilbertson, Nathaniel K. Szymczak, and David R. Tyler, J. Am. Chem. Soc. 2005, 127, 10184-10185.

Organometallic Chemistry in Aqueous Solution. Reactions Catalyzed by Water-Soluble Molybdocenes. Kerry L. Breno, Takiya J. Ahmed, Michael D. Pluth, Christoph Balzarek, and David R. Tyler, Coordination Chemistry Reviews, 2006, 250, 1141-1151.

Solution Chemistry of a Water-Soluble _2-H2 Ruthenium Complex: Evidence for Coordinated H2 Acting as a Hydrogen Bond Donor. Nathaniel K. Szymczak, Lev N. Zakharov, and David R. Tyler. J. Am. Chem. Soc., 2006, 128, 15830-15835.

Detection of hydrogen bonding in solution: A 2H nuclear magnetic resonance method based on rotational motion of a donor/acceptor complex. Nathaniel K. Szymczak, Alan B. Oelkers, and David R. Tyler. Physical Chemistry Chemical Physics, 2006, 4002-4008.

Coordination Chemistry of H2 and N2 in Aqueous Solution. Reactivity and Mechanistic Studies using trans-FeII(P2)2X2-type Complexes (P2 = a Chelating, Water-Solubilizing Phosphine). John D. Gilbertson, Nathaniel K. Szymczak, Warren K. Miller, David K. Lyon, Bruce M. Foxman, Joclyn Davis, David R. Tyler. Inorg. Chem., 2007, 46, 1205 -1214.

Femtosecond Pump-Probe Transient Absorption Study of the Photolysis of [Cp'Mo(CO)3]2 (Cp' = h5-C5H4CH3); The Role of Translational and Rotational Diffusion in the Radical Cage Effect. Alan B. Oelkers, Lawrence F. Scatena, and David R. Tyler. Journal of Physical Chemistry A, 2007; 111(25); 5353-5360.

The Radical Cage Effect; Is There a Spin Barrier to Recombination of Transition Metal Radicals? John D. Harris, Alan B. Oelkers, and David R. Tyler. J. Am. Chem. Soc., 2007, 129(19); 6255-6262..

Additional Publications

To Contact Dr. Tyler:
Phone: 541-346-4649
dtyler@uoregon.edu

WEBMASTER
chem@uoregon.edu