Green Catalytic Chemical Transformations

Our research interest can be broadly defined as in the area of transition metal catalysis. Currently our group is engaged in research areas aimed at designing homogeneous catalysts for the efficient transformation of our chemical feedstocks into high value products. Our research will encompass many areas, from the development of useful synthetic organic methodologies for organic chemistry, to the mechanistic principles that underlie catalytic reactions.

Ison research program

Projects

1. Catalytic Aerobic Oxidation

(a) Iridium Catalyzed Oxidation Chemistry

iridium catalyzed aerobic oxidation

There have been several reports on palladium catalyzed oxidations that undergo direct oxidations under catalytic turnover without a redox active co-catalyst. These discoveries have regenerated interests in the design and discovery of new metal systems that undergo similar ‘green oxidations’. Our group is engaged in a program that utilizes cationic Ir(III) complexes for aerobic oxidations.

Iridium Catalyzed Oxidation Chemistry

Jiang, B.; Feng, Y.; Ison, E. A. J. Am. Chem. Soc. 2008, 130(44), 14462-14464

(b) Catalytic Oxidations with Nitrous Oxide, N2O

An example of a Pd catalyzed aerobic oxidation is depicted (Sheldon et al Chem. Commun., 1998, 2359-2360). 1-hexene is oxididized with ½ O2 to give 2-hexanone using the Pd catalyst, [Pd(bathocuproinedisulfonic acid)(OAc)2], 1 mol %, H2O, NaOAc (1 eq), air (30 bar), 1000C.

Nitrous oxide, N2O, is an attractive alternative to traditional stoichiometric oxidants as the byproduct of its redox reactions is N2. Further, nitrous oxide has been shown to be a green house gas with a climatic forcing factor 315 times as great as CO2. It is also responsible for the indirect delivery of nitric oxide, NO, into the stratosphere, which catalyzes the depletion of the ozone layer. Recently, there have been a few examples of transition metal catalyzed oxidations utilizing high oxidation state Ru and Mo complexes, however, research utilizing N2O as an oxidant in transition metal catalyzed oxidations is still in its infancy. We will examine the use of electrophillic transition metal complexes as potential catalysts for N2O oxidations.

2. Direct Activation of Syngas to Acetic Acid

This research program is aimed at acquiring a fundamental understanding of the conditions, kinetics, and reactivity of key intermediates that may be present in homogeneous systems for syngas activation to C2+ oxygenated products.  This knowledge will lead to the rational design of new systems for homogeneous CO hydrogenation that are selective for the formation of C2+ oxygenates.  Preliminary results in our lab are promising for the developmentof a new catalytic system, based on high valent oxo rhenium species, for the formation of acetic acid from syngas.  However, the mechanistic insight gained from the research prrogram will also lead to the development of catalysts for the formation of other C2+ oxygenated products and the discovery of oxometal catalysts that feature cheaper earth abundant metals.

acyl to oxo

3. C-H Activation and Functionalization of Hydrocarbons

As a part of the Center for Enabling New Technologies through Catalysis (CENTC), and in colloboration with Karen Goldberg and Mike Heinekey (University of Washington), Bill Jones (University of Rochester), and Melanie Sanford (University of Michigan), another research area involves the development of catalysts for the activation and functionalization of C-H bonds of hydrocarbons. There has been recent interests in this area because of diminishing petroleum supplies and the desire to selectively oxidize natural gas (which is > 90% methane) to methanol, which can subsequently be utilized as a chemical feedstock or transportation fuel.

Currently we are utilizing Cp*Ir(III) complexes to activate and functionallize aromatic C-H bonds. The mechanistic insight gained from these studies will lead to the development of catalysts that can activate and functionalize other types of C-H bonds as well, including methane.

hd exchange

Feng, Y.; Jiang, B.; Boyle, P. D.; Ison, E. A. Organometallics 2010, 29, 2857

4. Catalytic Oxidation Chemistry Aimed at Upgrading Lignin

In collaboration with Dimitris Argyropoulos (NCSU, Department of Forest Biomaterials) and Reza Ghiladi (NCSU Chemistry), we are exploring the use of supercritical oxidation technologies for fragmenting and converting lignins into high value, low molecular weight chemicals. The project will use softwood and hardwood lignin streams that emerge from modern biomass/bio-energy saccharification treatments as well as organosolv pulping and kraft lignin streams. In order to fully utilize lignin as a sustainable chemical feedstock more efficient catalysts for its oxidative degradation will be designed.

lignin degradation

5. Development of Green Chemistry Experiments for the Undergraduate Laboratory

Our focus is on developing experiments for upper level chemistry laboratory courses. The areas of green chemistry and catalysis are of particular interest as they offer a unique opportunity for interdisciplinary research.

Undergraduate research is currently being done in conjunction with the lab development program described above. Students are fully engaged in the research process as they obtain hands on experience learning the full spectrum of synthetic and analytical techniques.

This program has so far been very successful. During summer 2008, two undergraduate students (Grace Kan, Matt Lehman) completed the synthesis, characterization and epoxidation using Jacobsen’s catalyst. Thanks to their work, this experiment is now ready for the classroom.