This research will explore the reactivity and structural chemistry of tervalent nickel in coordination environments which are thought to mimic those found for nickel hydrogenase enzymes. These enzymes are responsible for the reversible conversion of of hydrogen--an essential conversion in anaerobic metabolism for both chemotrophic and phototrophic bacteria. The coordination environment of the nickel site varies with different organisms. A consensus coordination sphere has 2-4 nitrogen or oxygen donors and 1-3 sulphur or selenium donors around nickel. Stabilization of nickel in its tervalent oxidation state will be a significant synthetic challenge due to the propensity of these systems to degrade by disulfide formation and concomitant metal reduction. A new class of ligands based on triazacyclononane will be designed and synthesized to circumvent this problem. The incorporation of other metals in this unique coordination environment will also be investigated. %%% This award is made as the starter grant increment of Dr. Daniel Stack's Postdoctoral Research Fellowship in Chemistry in support of his research at Stanford University. The thrust of Dr. Stack's research is the design, synthesis and characterization of analogs of nickel hydrogenases.
