Catalysis by organometallic complexes in supercritical carbon dioxide

Date of Completion

January 2003

Keywords

Chemistry, Organic|Engineering, Chemical

Degree

Ph.D.

Abstract

A novel fluorinated 2,2′-bis(diphenylphosphino)-1,1 ′-binaphthyl (BINAP) was developed with OCF3-substitution of the aryl groups in BINAP skeleton. Rate expression was developed for tiglic acid hydrogenation in methanol catalyzed by fluorinated ruthenium-BINAP as well as by the conventional ruthenium-BINAP complexes. The basic idea of the mechanism operating in this case was also provided. The ruthenium complexes of the new ligand (P-OCF3)BINAP exhibited different reactivity and enantioselectivity from those of BINAP for the enantioselective hydrogenation of tiglic acid in methanol. Typically, the ruthenium complexes of the new ligand (P-OCF3)BINAP has lower reactivity but has higher enantioselectivity at a high hydrogen pressure than those of BINAP at the same condition. The effect of OCF3 groups on the catalytic properties was also discussed on the basis of NMR spectra and kinetic data. Fluorinated ruthenium-BINAP complexes show to have sufficiently high solubility in dense CO2 for homogeneous catalytic reactions and those complexes were applied in the tiglic acid hydrogenation in CO2. Preliminary results show that CO2 has great influence in both the reactivity and enantioselectivity and methanol can be added into CO2 to increase the enantioselectivity. Catalysis by water-soluble complexes in water-in-CO2 (W/CO 2) microemulsions was also investigated. The sodium salt of bis(2,2,3,3,4,4,5,5-octafluoro-1-pentyl)-2-sulfosuccinate (di-HCF4) was used as a surfactant to stabilize W/CO2 microemulsions under a range of conditions. The phase behavior of the surfactant/water/CO 2 system was explored using cloud-point measurements for [di-HCF4] = 0.1–0.4 M, temperatures up to 55°C, and pressures up to 420 bar, yielding the highest water and surfactant concentration ever achieved for W/CO2 microemulsion systems at comparable pressures. Stable microemulsions at [di-HCF4] = 0.1 M were studied by small-angle X-ray scattering over the range of water-to-surfactant molar ratio from 0.5 to 20. The micelles were observed to swell as water was added to the core. A method for catalyst recovery and recycle in a W/CO2 microemulsion system was proposed. Olefins were hydroformylated in W/CO2 microemulsions in the presence of organometallic catalysts formed in situ from Rh(CO)2acac and 3,3 ′,3″-Phosphinldynetris (benzenesulfonic acid), trisodium salt (TPPTS) in the presence of synthesis gas. The effects of the presence of salts and acid on the stability of microemulsions and activity were also investigated. ^

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