Joint Director’s Special Colloquium & Chemical Sciences and Engineering Colloquium: ‘Catalytic Reduction of Nitrogen to Ammonia with Molybdenum Catalysts’
Richard Schrock, Nobel laureate in chemistry and Frederick G. Keyes Professor of Chemistry at the Massachusetts Institute of Technology, will present “Catalytic Reduction of Nitrogen to Ammonia with Molybdenum Catalysts” at a Joint Director’s Special Colloquium & Chemical Sciences and Engineering Colloquium.
The event takes place Wednesday, Oct. 4, 2017, at 10:30 a.m. in the Building 402 Auditorium. All employees whose schedules permit are invited to attend. Refreshments will be served.
Shuttle service will be provided beginning at 9:45 a.m. with first stop at Building 201, then stops at 212, 202, 223, 203, 200, 205 and 362 to Building 402. Return trips will follow the talk.
The first system for reduction of nitrogen to ammonia (2003) was a molybdenum catalyst that contains a tetradentate tren-based triamidoamine(3-) ligand ([N(CH2CH2N(HIPT))3]3-) in which HIPT is 3,5-(2,4,6-triisopropylphenyl)2C6H3 (1). In an effort to improve upon this catalyst we have turned to the synthesis of a ligand variation (H32) that we felt should be relatively stable toward removal through protonation under reducing conditions. We have now prepared Mo=N and shown that under the conditions successful for (1) as a catalyst for nitrogen reduction, Mo=N is does not reduce nitrogen catalytically, a problem that we think can be traced to a restricted access of the metal by reagents. A variation in which three of the methoxides in the “linkers” in the ligand have been removed and replaced by H is currently being explored. A Mo-based catalyst (3) that contains a conformationally rigid pyridine-based diamido ligand, [2,6-(ArNCH2)2NC5H3]2- (Ar = 2,6-disopropylphenyl; X = t-Bu, Cl, OTf, OC6F5), turns out to produce ~8 equivalents of ammonia in a batch-wise reduction of dinitrogen with CoCp*2 and Ph2NH2OTf in diethyl ether. The only variation so far that leads to a convincingly catalytic reduction of dinitrogen is that in which X = O-t-Bu. These results will be contrasted and compared with catalyst systems published by Nishibayashi and Peters. In all systems metallocenes are the optimum reducing agents and amines or anilinium salts are the proton sources.
Chemist and Nobel laureate Richard R. Schrock is the Frederick G. Keyes Professor of Chemistry at the Massachusetts Institute of Technology. In 2005 he received the August Wilhelm von Hofmann Medal from the German Chemical Society and shared the Nobel Prize in chemistry with Y. Chauvin and R. H. Grubbs.
Schrock discovered hydrogen abstraction reactions in high oxidation state metal alkyl complexes that yield high oxidation state “carbene” (alkylidene) and “carbyne” (alkylidyne) complexes. High oxidation state alkylidene complexes (“Schrock carbenes”) are the active catalysts for the olefin metathesis reactions, and much effort has been expended in learning how to design, synthesize, and control the activity of olefin metathesis catalysts. He also showed that alkylidyne complexes (again high oxidation state) were the active species in the acetylene metathesis reaction, and that alkylidynes could be prepared in a reaction between metal-metal triple bonds and acetylenes.
Schrock obtained his B. A. degree from the University of California at Riverside. He attended graduate school at Harvard University, from which he received his Ph. D. He has received the ACS Award in Organometallic Chemistry (1985), the Harrison Howe Award of the Rochester ACS section (1990), the ACS Award in Inorganic Chemistry (1996), the Bailar Medal from the University of Illinois (1998), an ACS Cope Scholar Award (2001), the F. Albert Cotton Award in Synthetic Inorganic Chemistry (2006), the Theodore Richards Medal from the Northeast ACS section (2006), and the Basolo Medal from the Chicago ACS section (2007). He has been elected to the American Academy of Arts and Sciences, the National Academy of Sciences, and the Royal Society of London. He was Associate Editor of Organometallics for eight years, has published more than 590 research papers and has supervised over 180 Ph.D. students and postdocs.