MC 3102

work:+1 212-854-7644

jrn11@columbia.edu

Research Summary

Our research interests cover broad areas of organometallic chemistry and bioinorganic chemistry. The central theme is catalysis. Although we approach problems in a mechanistic way, and use a variety of physical methods, we also synthesize new compounds, ranging from models for metalloenzymes through organometallics to small organic compounds.

Much of our work lies at the interface between inorganic and organic chemistry. We have reported the asymmetric synthesis of -amino acid amides and esters from zirconaaziridines. By using a chiral carbonate we can achieve a dynamic kinetic resolution (or "asymmetric transformation"). The stereochemical outcome depends upon the rate of configuration change of the carbon in the zirconaaziridine ring, so we are studying how this change in stereochemistry occurs. By using related electrophiles (carbodiimides) we can prepare a-amino amidines with control of stereochemistry. We hope that, by using epoxides and/or aziridines as electrophiles, we can devise a general method for preparing and controlling the stereochemistry of 1,3-N,O- and 1,3-N,N-disubstituted carbon chains.

We are also:

1. measuring indirectly the rate at which Fe(II) is taken up by the apoproteins of ribonucleotide reductase and other metalloproteins. While the uptake of Fe(II) causes too little change in the visible spectrum to permit its direct observation, its rate can be deduced from the effect of the apoprotein on the rate of formation of the readily observable complex Fe(II)(ferrozine)₃
2. using metalloradicals such as (C₅Ph₅)Cr(CO)₃)- as catalysts for chain transfer in radical polymerizations. The metalloradical removes Ho from the chain-carrying radical and starts a new chain by transferring it to a monomer.
3. investigating the importance of one-electron reduction in the chemistry of electrophilic boranes such as (C₆F₅)₃B. These boranes are used to activate catalysts for olefin polymerization.
4. trying to improve the enantioselectivity of catalytic hydrogenations that occur by ionic mechanisms. In such reactions H+ and H- are generated from H₂ and transferred separately to the substrate.

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“Unusually Weak Metal-Hydrogen Bonds in HV(CO)₄(P-P) and Their Effectiveness as H• Donors” J. W. Choi, M. E. Pulling, D. M. Smith, J. R. Norton, J. Am. Chem. Soc. 130, 4250-4252 (2008)

“Direct Measurement of the Rate of Interconversion of Zirconaaziridine Enantiomers” S. A. Cummings, J. A. Tunge, J. R. Norton, J. Am. Chem. Soc. 130, 4669-4679(2008)

“Chain-Transfer Catalysis by Vanadium Complexes during Methyl Methacrylate Polymerization”, J. W. Choi, J. R. Norton, Inorg. Chim. Acta (Special Issue, Robert J. Angelici) in press (2008)

“Synthesis and Properties of Carboxy-Substituted Half-Sandwich Ruthenium Complexes with Chelating Bisphosphine Ligands (η⁵-C₅H₄CO₂H)Ru(η²-L)X (X = I, H)”, A. P. Shaw, H. Guan, J. R. Norton,J. Organomet. Chem 693, 1382-1388 (2008)

“Enantioselective Methylalumination of a-Olefins”, R. A. Petros, J. M. Camara, J. R. Norton, J. Organomet. Chem.(Special Issue, Gerhard Erker) 692, 4768-4773 (2007)

“Electron Exchange Involving a Sulfur-Stabilized Ruthenium Radical Cation” A.P. Shaw, B.L. Ryland, J.R. Norton, D. Buccella, A. Muscatelli; Inorg. Chem. 46, 5805-5812 (2007)

“Tin-Free and Catalytic Radical Cyclizations” D. M. Smith, M.E. Pulling and J.R. Norton; J. Am. Chem. Soc. 129, 770-771 (2007)

"Kinetics of Hydrogen Atom Transfer from (C₅H₅)Cr(CO)₃H to Various Olefins: Influence of Olefin Structure" Choi, J., Tang, L., Norton, J. R., J. Am. Chem. Soc. 129; 234-240 (2007)

"Measurement of the Rate Constant for Hydroden Atom Abstraction from Methylisobutyryl Radical by (C₅Ph₅)Cr(CO)₃ Radical" Tang, L., Norton, J. R., Macromolecules 39; 8236-8240 (2006)

"Factors Affecting the Apparent Chain Transfer Rate Constants of Chromium Metalloradicals: Mechanistic Implications" Tang, L., Norton, J. R., Macromolecules39; 8229-8235 (2006)

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