The Goldberg group seeks to develop new catalytic systems to produce chemicals and fuels from a range of available feedstocks via environmentally responsible and economically viable processes. Below are some of the ongoing projects in our laboratory.
Selective C-H oxidations
Natural gas is comprised of methane and light alkanes. Currently available methods, primarily using heterogeneous catalysts, to convert natural gas to chemicals and liquid fuels use enormous amounts of energy and such production facilities require considerable capital investment. It is also expensive to build gas pipelines. These challenges result in a large amount of gas being flared (burned to CO2).
Our goal is to develop homogeneous metal complexes that will be able to selectively activate and transform methane and light alkanes to chemicals and liquid fuels by low energy and low-cost processes. To accomplish this, our group is investigating new modes of C-H activation that will be able to operate under aerobic conditions (see next section). For example, we are preparing new compounds wherein C-H bonds are activated by concerted-metalation deprotonation (CMD) or metal-ligand cooperation (MLC).
Oxygen as an Oxidant
The optimal oxidant for large-scale oxidations is O2 in air. O2 is the cleanest and greenest oxidant. It is environmentally benign, readily available and inexpensive, particularly if it can be used without separation from air. Notably, of the 16 top organic oxidations carried out commercially, 14 use O2 or air as the oxidant. However, to make propylene oxide (PO), which is produced annually on the mega-ton scale (5th largest oxidation), industry currently uses Cl2, alkyl hydroperoxides or hydrogen peroxide as oxidants. These indirect routes carry significant costs including safety concerns in handling toxic reagents, costly waste stream treatment, co-product dependencies and/or large capital investments. A process for the direct reaction of O2 with propylene to form PO would be a “game changer” in the chemical industry. We are investigating catalytic systems like that shown below by studying the individual mechanistic steps of the cycle.
Bailey, W. D.; Phearman, A. S.; Luconi,L.; Rossin, A.; Yakhvarov, D.; D’Accolti, L.; Flowers, S. E.; Kaminsky, W.; Kemp, R. A.; Giambastiani, G.; Goldberg, K. I. Chem. Eur. J. 2019, 25, 9920-9929.
Fulmer, G. R.; Herndon, A. N.; Kaminsky, W.; Kemp, R. A.; Goldberg, K. I. J. Am. Chem. Soc. 2011, 133, 17713-17726.
Denney, M. C.; Smythe, N. A.; Cetto, K. L.; Kemp, R. A.; Goldberg, K. I. J. Am. Chem. Soc. 2006, 128, 2508.
Similarly, we are pursuing direct aerobic oxidations of alkane to alcohol and olefins. These would be extremely valuable commercial reactions. We are investigating several potential catalytic cycles including the ones shown below.
Wright, A. M.; Pahls, D. R.; Gary, J. B.; Warner, T.; Williams, J. Z.; Knapp, S. M. M.; Allen, K. E.; Landis, C. R.; Cundari, T. R.; Goldberg, K. I. J. Am. Chem. Soc. 2019, 141, 10830-10843.
Allen, K. E.; Heinekey, D. M.; Goldman, A. S.; Goldberg, K. I. Organometallics 2014, 33, 1337-1340.
Zeitler, H. E.; Kaminsky, W. A.; Goldberg, K. I. Organometallics 2018, 37, 3644-3648.
Smoll, K. A.; Kaminsky, W.; Goldberg, K. I. Organometallics 2017, 36, 1213-1216.
Boisvert, L.; Denney, M. C.; Hanson, S. K.; Goldberg, K. I. J. Am. Chem. Soc. 2009, 131, 15802-15814.
Grice, K. A.; Goldberg, K. I. Organometallics 2009, 28, 953-955.
CO2 to chemicals and liquid fuels
The future sustainability of our society will depend on the efficient management of the available carbon feedstocks. Currently, the fast rate of fossil fuel exploitation to power anthropogenic activities has led to the accumulation of CO2 in the atmosphere without effective means to recycle this highly oxidized carbon material back into the industrial supply chain. To restore balance to the carbon-cycle, our group is investigating catalytic reductions of CO2 into useful chemical feedstocks and liquid fuels.
Methanol is one of the most valuable chemicals that arises from hydrogenation of CO2 and it is one of the targets our group is pursuing. In addition to its wide usage in industry, catalytic transformation of MeOH into higher alkanes is an industrially employed process, making it a compelling candidate as a synthetic fuel precursor. Our group has been investigating selective catalytic routes to reduce CO2 to MeOH. Successful implementation of such a process would decrease our dependence on petroleum resources.