Prof. Mark E. Noble
Metal-sulfur compounds play numerous roles in vastly important biological and industrial processes. Biological systems, from bacteria through humans, use a variety of metal-sulfur complexes in a range of proteins and enzymes. The list grows longer on a yearly basis as more and more metallosulfur bioprocesses are characterized. By far the most important of these is biological nitrogen fixation; this is the second most important agricultural process on Earth, and most life on Earth is dependent on this process. Industry uses metal-sulfur compounds as catalysts in various processes. The largest of these is hydrodesulfurization which is the largest industrial throughput process on Earth. This is a critical and early step in the processing of crude fuels. Crude fuels contain an assortment of sulfur compounds and it is essential to eliminate as much of these as possible.
With just these few examples, the importance of metal-sulfur compounds is evident. Research in our laboratory investigates the fundamental chemistry of metal-sulfur complexes, with emphasis on the sulfur chemistry and not on the metal. There is an extremely wide breadth to this reactivity: the sulfur sites have displayed well characterized nucleophilic, radical and electrophilic mechanisms. Most of the work has utilized dimeric molybdenum-sulfur complexes although some tungsten compounds have also been investigated. The molybdenum connection arises from the importance of Mo as an important metal (with Fe) in biological nitrogen fixation and also as an important metal used in hydrodesulufurization catalysts. The Mo-S combination is extremely versatile, as demonstrated by the range of applications for which it is so critical. Recent efforts are directed at the reactivity of S-O linkages, including alkylation and protonation chemistry. This work has proven quite rich. Previous work has included S-N, S-halogen and S-C linkages and their chemistry.
Alkylation of a Dimolybdenum SO Bridge, Subsequent Reactions, and Characterization
of the Thioperoxide Bridge
C. M. Tuong, W. K. Hammons, A. L. Howarth, K. E. Lutz, A. D. Maduvu, L. B. Haysley, B. R. T. Allred, L. K. Hoyt, M. S. Mashuta, M. E. Noble, Inorg. Chem. 2009, 48, 5027 - 5038.
Greening the Blue Bottle
W. K. Wellman, M. E. Noble, J. Chem. Educ. 2003, 80, 537 - 540.
Out of the Blue
M. E. Noble, J. Chem. Educ. 2003, 80, 536A - 536B.
Activation of Ligand Reactivity: Thiolate C-S and Dithiophosphate Ester C-O Heterolyses Within a Dimolybdenum(V) System
E. I. Koffi-Sokpa, D. T. Calfee, B. R. T. Allred, J. L. Davis, E. K. Haub, A. K. Rich, R. A. Porter, M. S. Mashuta, J. F. Richardson, M. E. Noble, Inorg. Chem. 1999, 38, 802 - 813.
Oxidation at a Dimolybdenum(V) Sulfur Bridge. Formation of SO and SO2 Bridges. Facile Extrusion of SO from the SO2 Bridge
R. Wang, M. S. Mashuta, J. F. Richardson M. E. Noble, Inorg. Chem. 1996, 35, 3022 - 3030.
Halogenation at a Dimolybdenum(V) and Ditungsten(V) Sulfur Bridge: Metallosulfenyl Halides M2(µ-SX) and [M2(µ-SX3)]n. Charge Transfer Interactions
J. Q. Lee, M. L. Sampson, J. F. Richardson, M. E. Noble, Inorg. Chem. 1995, 34, 5055 - 5064.
Reactions at a Dimolybdenum(V) Sulfur Bridge: Metallothionitrites and the NO2-, NO, NO+ Connection
E. K. Haub, A. C. Lizano M. E. Noble, J. Am. Chem. Soc. 1995, 34, 1440 - 1444.
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