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Final Report: Green Oxidation Catalysts for Fine Chemical Synthesis
EPA Grant Number: R829553Title: Green Oxidation Catalysts for Fine Chemical Synthesis
Investigators: Shapley, Patricia A.
Institution: University of Illinois at Urbana-Champaign
EPA Project Officer: Savage, Nora
Project Period: January 1, 2002 through December 31, 2004
Project Amount: $325,000
RFA: Technology for a Sustainable Environment (2001)
Research Category: Pollution Prevention/Sustainable Development
Description:
Objective:The objective of this research project is to synthesize a series of new heterometallic oxidation catalysts with a range of steric and electronic properties as a “toolbox” of catalysts. Ideally, each of these would be effective for the oxidation of only one functional group in a particular substrate. Chiral catalysts would be used for asymmetric oxidations. Molecular oxygen and hydrogen peroxide will be the only stoichiometric oxidants used. An additional objective is to find methods for the chemical transformation of agricultural products, such as fatty acids from soy, to fine chemicals. We also intend to prepare water-soluble catalysts for the oxidation of carbohydrates. To reduce the quantity of volatile organic solvents used in oxidation reactions, we will test water-soluble complexes for catalytic activity in water. Some complexes will be tested in alternative solvents, such as supercritical CO2. Supported metal complexes will be tested as heterogeneous catalysts.
Summary/Accomplishments (Outputs/Outcomes):The fine chemical industries require more selective, robust catalysts for the oxidation of single functional groups in complex precursors with molecular oxygen. This project has been directed toward the development of new, green alternatives to current oxidation processes. In the period since this project was funded by the U.S. Environmental Protection Agency, we moved our studies on catalysis in the selective oxidation of organic molecules from our initial results with Os(VI)/Cr(VI) and Ru(VI)/Cr(VI) bimetallic catalysts to a series of new heterometallic catalysts that include Ni(II), Pd(II), or Pt(II) along with Os(VI) or Ru(VI). We synthesized and characterized these new organometallic molecules. We also examined their activity in the oxidation of alkene and alcohol substrates in typical organic solvents as well as in supercritical carbon dioxide. For the catalytic oxidation of C-H bonds, we examined iron-based oxidants and catalysts. Stereoselective oxidation reactions require either chiral reagents or chiral catalysts. We have completed a project on the synthesis of chiral-at-metal osmium(VI) complexes that we plan to use as precursors to chiral catalysts.
We developed a rational synthesis of µ-sulfido complexes of Os(VI) or Ru(VI) with either Ni(II), Pd(II), or Pt(II) through a bridge-building reaction. New, sulfido-bridged heterobimetallic complexes L2M(µ3-S)2{M’(N)R2}2 resulted from the reactions of (dppe)Pt(SSiMe3)2, (COD)Pt(SSiMe3)2, (dppe)Pd(SSiMe3)2, or (dppe)Ni(SSiMe3)2 with [PPh4][Ru(N)Me2Cl2] or [Os(N)(CH2SiMe3)2(NCMe)2][BF4]. All of the complexes catalyze the oxidation of benzyl alcohol to benzaldehyde with molecular oxygen. Rates and turnover numbers were similar for each oxidation reaction in a typical organic solvent, toluene, and in a more environmentally friendly solvent, supercritical CO2.
To avoid catalyst decomposition and improve activity, we developed a new route to µ-oxo heterometallic complexes from the osmium(VI) and ruthenium(VI) precursors [N(n-Bu)4][cis-M′ (N)(OH)2R2] and [M′ (N)(OH)R2]2 (M′=Ru, Os). These react with a wide variety of trimethylsiloxy complexes M″(OSiMe3)2Lx to form new complexes that are potentially more robust oxidation catalysts. Many of these catalysts can be supported on silica and retain the selectivity of the homogeneous catalysts.
We prepared Ru/Pd heterometallic complexes, [Y][Ru(N)(CH3)2(µ-O)2Pd((-)-sparteine)] where Y is PPh4 or N(n-Bu)4, by the reaction of the hydroxo complex [Y][Ru(N)(CH3)2(OH)2] with Pd((-)-sparteine)(OSiMe2)2. At 60ºC, in air, this Ru/Pd complex oxidized aryl and allylic alcohols to their corresponding aldehydes.
We examined the oxidation of fatty acids with hydrogen peroxide catalyzed by Fe(III) complexes. The oxidation of butanoic acid with H2O2 in the presence of [[N(n-Bu)4][FeCl4] was unselective with products resulting from initial reaction at C2, C3, and C4. A picolinate complex, [PPh4][Fe(pic)2Cl2], is an active catalyst for the oxidation of carboxylic acids with hydrogen peroxide. The linear C3-C8 acids (propanoic-octanoic acids) are initially hydroxylated at the alpha carbon. The primary product is further oxidized under reaction conditions.
Asymmetric catalysts are a key to the selective synthesis of fine chemicals and pharmaceuticals. We have been able to prepare and separately isolate diastereomeric complexes that are chiral at the osmium center. Racemic [N(n-Bu)4][cis-Os(N)Ph(CH2SiMe3)Cl2] results from a series of alkylation and protonation reactions on [N(n-Bu)4][Os(N)Cl4]. (S,S)-Chiraphos displaces a chloride from this complex to produce two isomers of Os(N)Ph(CH2SiMe3)Cl((S,S)-chiraphos) with different configurations at osmium. By exploiting the very different rates of chloride dissociation in the two complexes, we can isolate each separately. More reactive complexes, diastereomers of cis-Os(N)Ph(CH2SiMe3){(R)-NH2CHMePh}2Cl, like those of Os(N)Ph(CH2SiMe3)Cl((S,S)-chiraphos), are also easily separable without isomerization of the metal center. These may be good precursors to asymmetric heterometallic catalysts.
Journal Articles on this Report : 3 Displayed | Download in RIS Format
| Other project views: | All 16 publications | 7 publications in selected types | All 5 journal articles |
| Type | Citation | ||
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Kuiper JL, Shapley PA. Synthesis, structure, and reactivity of the ruthenium(VI)-Nickel(II) complex (dppe)Ni(µ3-S)2 {Ru(N)Me2}2. Organometallics 2004(16); 23:3814-3818. |
R829553 (2004) R829553 (Final) |
not available |
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Lutz CM, Wilson SR, Shapley PA. The first imido complex of osmium(VI), [CpOs(NH)(CH2SiMe3)(2)][SO3CF3]. Organometallics 2005;24(13):3350-3353 |
R829553 (Final) |
not available |
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Pool DH, Shapley PA. Chiral-at-metal osmium(VI) phosphine complexes. Organometallics 2004; 23(10):2326-2335. |
R829553 (2004) R829553 (Final) |
not available |
green chemistry, chemicals, oxidants, oxidation, renewable, molecular oxygen, hydrogen peroxide, heterometallic oxidation catalysts, chiral catalysts,
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Sustainable Industry/Business, Scientific Discipline, RFA, Technology for Sustainable Environment, Sustainable Environment, Chemical Engineering, cleaner production/pollution prevention, Environmental Chemistry, Chemistry and Materials Science, New/Innovative technologies, supercritical carbon dioxide, solvent replacements, chemical transformation, catalytic transformations, carbon dioxide, environmentally-friendly chemical synthesis, Volatile Organic Compounds (VOCs), waste reduction, renewable feedstocks, agricultural industry, green oxidation catalyst, "toolbox" of catalyst, catalysts, green chemistry, solvents, oxidation, oxidation reactions, chemcial synthesis, pharmaceutical industry, chemical synthesis, fine chemicals, solvent substitute, supercritical carbon dioxide (SCCO2) technology, pollution prevention
Progress and Final Reports:
2002 Progress Report
2004 Progress Report
Original Abstract