Research in the Chirik group is at the intersection of the traditional disciplines of organic and inorganic chemistry. The discovery of sustainable methods in chemical synthesis is a unifying theme in our projects. One area of long-standing interest is the discovery of new reactions for the functionalization of atmospheric nitrogen. A second interest is base metal catalysis and the elucidation of the electronic structure of redox-active metal-ligand complexes with emphasis on the integration of spectroscopy and theory. With these goals in mind, we study transition metal complexes from across the periodic table and use state-of-the-art multinuclear NMR experiments, X-ray diffraction techniques, isotopic labeling, Mössbauer and EPR spectroscopy as well as modern DFT methods to establish the electronic and molecular structures of the compounds and pre-catalysts we prepare.
Ongoing projects are:
• Base Metal Catalysis. Transition metal catalyzed reactions, such as olefin hydrogenation, hydrosilylation, cycloaddition, and polymerization, have emerged as an invaluable tool in chemical synthesis. Applications range from pharmaceutical process chemistry to the commodity scale production of silicone materials. Research in our laboratory seeks to replace the established precious metal catalysts used for these reactions with more abundant and environmentally compatible base metals such as manganese, iron and cobalt. Efficient base metal catalysts for olefin hydrogenation, hydrosilylation and polymerization have been developed. In addition, unique inter- and intramolecular [2π + 2π] reactions that take advantage of the electronic structure of the first row metal ions have also been discovered. Collaboration with industrial partners has also been established and offers inspiration for many of our targets.
• Electronic Structure of Redox-Active Metal Ligand Complexes. Understanding the fundamental reaction chemistry and electronic structures of first row metal complexes is core to our catalyst development effort. One motivation has been to enable two-electron redox chemistry in deference to more typical one-electron reactions that are observed with first row metal ions. To accomplish this objective, we have been exploring the chemistry of bis(imino)pyridine metal compounds. The redox-activity of the chelate, the ability to undergo smooth, reversible one electron transfer with the metal, often produces compounds whose formal oxidation state assignment is deceiving. In addition to fundamental reaction chemistry, we have been exploring the preparation and electronic structure of unusual iron and cobalt imido, oxo and reactive nitrido compounds.
• N2 Functionalization with Early Transition Metals. The synthesis of ammonia, NH3, from its elements, N2 and H2, is a challenge that has confronted chemists for the past century. While the venerable Haber-Bosch reaction is a key driver of modern society - this single reaction supports 40 % of the world's population and accounts for approximately half of the nitrogen in the human body - the energy inputs required for an economical industrial process renders crop fermentation products such as ethanol too energetically expensive to serve as replacements for fossil fuels. Many nitrogen-containing organic molecules rely on Haber-Bosch ammonia as the N-atom source. An area of long-standing interest in our laboratory has been the discovery of new reaction chemistry of the typically inert N2 molecule with the goal of converting it into more value-added organic molecules such as amides, heterocycles and amines.
Having discovered numerous methods for the synthesis of N-H bonds via 1,2-addition, we have recently turned our attention to methods for N-C bond forming reactions directly from N2. A noteworthy highlight in this area has been the discovery of CO-induced N2 bond cleavage where N≡N scission is coupled with formation of two N-C and one C-C bonds. The new oxamidide core, [N2C2O2]4-, serves as a building block for various organic molecules that are ultimately derived from N2 and CO, the diatomics with the two strongest bonds in chemistry.
We are currently exploring the generality of this transformation and determining the mechanism of N2 cleavage and N-C and C-C bond formation. In the long-term, new mechanistic paradigms for N2 cleavage, namely by fundamental organometallic reaction chemistry, are under active investigation.
Honors & Awards
- Closs Lecturer, University of Chicago (2014)
- Dalton Lecturer, University of California - Berkeley (2011)
- Winner, Blavatnik Award, New York Academy of Sciences (2009)
- Arthur C. Cope Scholar Award, American Chemical Society (2009)
- Bessel Fellow of the Alexander von Humboldt Foundation (2008)
- Camille Dreyfus-Teacher Scholar (2006)
- Stephen and Margery Russell Distinguished Teaching Award (2005)
- David and Lucile Packard Fellow in Science and Engineering (2004)
- NSF CAREER Award (2003)
- Herbert Newby McCoy Award for Outstanding Dissertation, Caltech (2000)
Selected Recent Publications
- Obligacion, J. V.; Chirik, P. J. “Bis(imino)pyridine cobalt-catalyzed alkene isomerization-hydroboration: A strategy for remote hydrofunctionalization with terminal selectivity.” J. Am. Chem. Soc. 2013, 135, 19107-19110.
- Friedfeld, M. R.; Shevlin, M.; Hoyt, J. M.; Krska, S. W.; Tudge, M. T.; Chirik, P. J. “Cobalt precursors for high throughput discovery of base metal asymmetric hydrogenation catalysts.” Science 2013, 342, 1076-1080.
- Semproni, S. P.; Chirik, P. J. “Synthesis of a base-free hafnium nitride from N2 cleavage: A versatile platform for dinitrogen functionalization.” J. Am. Chem. Soc. 2013, 135, 11373-11383.
- Semproni, S. P.; Knobloch, D. J.; Milsmann, C.; Chirik, P. J. “Redox-induced N2 hapticity switching in zirconocene complexes.” Angew. Chem. Int. Ed. 2013, 52, 5372-5376.
- Tondreau, A. M.; Atienza, C. C. H.; Weller, K. J.; Nye, S. A.; Lewis, K. M.; Delis, J. G. P.; Chirik, P. J. “Iron catalysts for selective anti-Markovnikov alkene hydrosilylation using tertiary silanes.” Science 2012, 335, 567-570.