Ligand effects on the catalytic reduction of perchlorate with supported Re(V) complexes

ENVR 177

Keith D. Hurley, kdhurley@uiuc.edu and John R. Shapley, shapley@uiuc.edu. Department of Chemistry and Center of Advanced Materials for the Purification of Water with Systems, University of Illinois at Urbana-Champaign, 505 S. Mathews, Urbana, IL 61801
The first heterogeneous catalyst for the efficient reduction of perchlorate with hydrogen in water involved the oxorhenium(VII) precursors Re(CH3)O3 and [ReO4]- supported on activated carbon together with metallic Pd nanoparticles. A Re(VII)/Re(V) redox cycle was proposed as a key component of the reduction process. Subsequently, the Re(V) complexes Re(O)(hoz)2Cl (Hhoz = 2-(2'-hydroxyphenyl)-2-oxazoline) and [Re(O)2(py)4]Cl (py = pyridine) have been demonstrated to serve as appropriate precursors for active catalyst preparations. The latter complex is easily modified by employing variously substituted pyridine ligands, e.g., NC5H4X, X = Cl, OCH3, N(CH3)2, etc. Kinetic data from the use of these compounds as catalyst precursors will be presented and the role of the ligand properties (electronic and steric) in affecting reactivity at the rhenium site will be discussed.