Homogeneous catalysis of decontamination-type reactions with organometallic and polyoxometalate manganese complexes
Abstract
Although a majority of the world’s declared stockpiles of chemical warfare agents have been eliminated, their danger and the need for efficient decontamination protocols still exist. The toxicity of these agents is a result of their phosphoester center or a sulfur moiety. In the case of nerve agent VX (ethyl S-diisopropylaminoethyl methyl phosphonothioate), both groups are present. Consequently, sulfide oxygenation, in addition to its other industrial applications, plays in important role in chemical warfare decontamination. The research presented herein explores the use of two types of complexes, based on the essential trace element manganese, as catalysts for sulfide oxygenation reactions. The first type of complex includes a pair of dimanganese organometallic compound with triazacyclononane terminal ligands and oxo- or carboxylato-bridging ligands. When used with a 0.15 mol% loading and 12 equivalents of hydrogen peroxide, these compounds effectively catalyze the oxygenation of several organic sulfide substrates, including methyl phenyl sulfide, phenyl sulfide, and 4-bromothioanisole. The second complex reported in this research is (NH4) 6MnMo9O32, a polyoxometalate with a manganese (IV) center. A novel, easy synthetic route to obtain this complex is presented along with activity studies for catalytic sulfide oxygenation. Unlike the dimanganese complexes, (NH4)6MnMo9O 32 can be tuned for both aqueous and organic solutions, allowing for a wider substrate scope. At 1 mol% catalyst loading, and 2 equivalents of hydrogen peroxide, (NH4)6MnMo9O32 allows for rapid oxygenation of the same organic sulfide substrates mentioned above as well as other chemical warfare agent simulants like phenylthioethanol, chloroethyl ethyl sulfide, and chloroethyl phenyl sulfide. The polyoxometalate also shows promise for being a dual purpose catalyst as proven by its use in promoting phosphoester hydrolysis.
Degree
M.S.
Advisors
Ren, Purdue University.
Subject Area
Chemistry|Inorganic chemistry
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