CHED 1200 |
| A juxtaposition of donor types are essential to modeling the redox chemistry of nickel enzymes and proteins. Ni(III)-Ni(II)-Ni(I) redox cycles have been proposed as part of the enzymatic activity of Methyl-CoM reductase, NiFe Hydrogenase and NiSOD. Importantly, it has been found that the nickel sites in redox enzymes are dominated by sulfur ligation, whereas nickel hydrolytic enzymes and transport enzymes are dominated by O/N- donors. We have extensively studied the coordination chemistry of thioether oxime based ligands1, 2 and have found that he presence of an oximate nitrogen in the coordination sphere on nickel(II) tends to stabilize Ni(III), whereas thioether donors tend to support Ni(I). In some cases the number and type of donors of sulfur and oxime donors allows both oxidation and reduction of nickel(II) to occur 2. The Ni(III)-Ni(II)-Ni(I) redox cycle is difficult to achieve in small molecule chemistry, since the environment necessary for stabilizing Ni(I) is much different from that which stabilizes Ni(III). To further our understanding of these systems we explored the nickel(II) coordination chemistry of 3-methyl-3-(pyridin-2-ylsulfanyl)butan-2-one oxime (MePyrSuH). We have found that the bis-MePyrSu nickel(II) complex forms preferentially over other ligand/metal ratios. The x-ray crystal structure of the complex revealed the complex to have the formula [Ni(MePyrSu)(MePyrSuH)](ClO4). Where one of the MePyrSuH ligand retains its proton and is hydrogen-bonded to a MePyrSu- ligand. Spectroscopic and Electrochemical Data will also be discussed in light of nickel enzyme redox cycles. 1. M.J. Prushan, A.W. Addison, R. Butcher, J. Inorg. Chim. Acta 300–302 (2000) 992. 2. V.V. Pavlishchuk, S.V. Kolotilov, A.W. Addison, M.J. Prushan, R.J. Butcher, L.K. Thompson, Inorg. Chem. 38 (1999) 1759. |
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Undergraduate Research Poster Session: Inorganic Chemistry
2:00 PM-4:00 PM, Monday, April 7, 2008 Morial Convention Center -- Hall A, Poster
Division of Chemical Education |