New polyoxometalate heterogeneous and homogeneous catalytic systems for oxidation of thioethers and acetaldehyde under ambient conditions.

摘要

The work presented in this dissertation focuses on the synthesis, characterization and catalytic chemistry of transition metal salt polyoxometalates. Ag ₅PV₂Mo₁₀O₄₀, [CO(CH₃CN) ₄(H₂O)₂][{lcub}CH₃C(CH₂O) ₃{rcub}₂V₆O₁₃], and [Na₂{lcub}CH ₃C(CH₂O)₃{rcub}₂V₆O₁₃]·7H ₂O were all synthesized and evaluated as catalysts for the oxidation of thioether chemical warfare agent simulants (Ag₅PV₂Mo ₁₀O₄₀) and acetaldehyde ([Co(CH₃CN)₄(H ₂O)₂]-[{lcub}CH₃C(CH₂O)₃{rcub} ₂V₆O₁₃], and [Na₂{lcub}CH₃C(CH ₂O)₃{rcub}₂V₆O₁₃]·7H ₂O). Oxidation of chemical warfare agents is important for the battlefield protection of troops and equipment as well as “environmentally friendly” methods for the destruction of large stockpiles. Acetaldehyde and other aldehydes are indoor pollutants originating from the prevalent use of synthetic fabrics and construction materials. These compounds have recently been associated with toxicological effects in humans.; Chapter 1 provides a very brief and general overview of polyoxometalates (POMs). Included is a discussion of the basic structural chemistry of POMs and fields of application where POMs are utilized. Also included is a discussion of POMs as oxidation catalysts in thermal and radical chain initiated oxidations. Activation of molecular oxygen by POMs is also addressed.; Chapter 2 presents the synthesis, characterization and catalysis of Ag ₅PV₂Mo₁₀O₄₀. Under heterogeneous conditions, Ag₅PV₂Mo₁₀O₄₀, was found to be an effective catalyst for the selective oxidation of 2-chloroethyl ethyl sulfide (CEES, an analog for mustard (HD)) under ambient conditions (room temperature and air). The heterogeneous nature of the system prevented meaningful rate law determination. Absolute structural determination of Ag₅PV ₂Mo₁₀O₄₀ was accomplished by X-ray crystallography. When crystallized from MeCN and Et₂O Ag₅PV₂Mo ₁₀O₄₀ is a dimer of 2 PV₂Mo₁₀O ₄₀5− molecules linked by 2 bridging Ag(I) atoms.; Chapters 3 and 4 examine the synthesis and characterization of [Co(CH ₃CN)₄(H₂O)₂][(CH₃C(CH ₂O)₃{rcub}₂V₆O₁₃] and [Na ₂{lcub}CH₃C(CH₂O)₃{rcub}₂V₆O ₁₃]·7H₂O. Aside from standard methods of characterization (e.g. NMR, IR, elemental analysis, etc.), the structure of both complexes was determined by X-ray crystallography. The application of both catalysts for the heterogeneous oxidation of acetaldehyde at room temperature is presented along with rudimentary mechanistic information. A more rigorous and detailed examination of the rate law and mechanism for homogeneous acetaldehyde autoxidation under ambient conditions catalyzed by [Co(CH₃CN)₄(H ₂O)₂][(CH₃C(CH₂O)₃{rcub} ₂V₆O₁₃] is presented in Chapter 4.