Levente Nádasdi

Homogeneous hydrogenation of carbon dioxide and bicarbonate in aqueous solution catalyzed by water-soluble ruthenium(II) phosphine complexes

The water-soluble Ru(II)-phosphine complex, [{RuCl2(mTPPMS)(2)}(2)] was found a suitable catalyst for the hydrogenation of NaHCO3 to NaHCO2 in aqueous solution under mild conditions with catalyst turnover frequencies (TOFs) in the range of 35-50 h(-1) at 50degreesC and 10 bar total pressure. The suggested reaction mechanism involves the formation of Ru(II)-hydrides of the general formula [RuHX(mTPPMS)(4)] where X = H-, HCO3- or HCO2-. At 80degreesC and 95 bar total pressure, the reduction of NaHCO3 proceeded with high reaction rate (9600 h(-1)) hitherto unobserved in purely aqueous solutions. The reactions do not require the presence of organic amine additives, however, the addition of quinoline increased the rate considerably. Aqueous suspensions of calcium carbonate could also be hydrogenated with CO2/H-2 gas mixtures

Aqueous organometallic chemistry: the mechanism of catalytic hydrogenations with chlorotris(1,3,5-triaza-7-phosphaadamantane) rhodium(I)

Abstract The water-soluble phosphine complex of Rh(I), RhCl(PTA) 3 ( 1 ) was shown to be an active catalyst for the hydrogenation of various olefinic and oxo-acids, as well as of allyl alcohol and 4-sulfostyrene in aqueous solution under mild conditions. Detailed kinetic investigations were carried out with crotonic acid and allyl alcohol as substrates. The rate of hydrogenation of both compounds showed a sharp maximum as a function of pH at 4.7. Hydrogenation of itaconic, crotonic and α-acetamidocinnamic acid in D 2 O led to 45–100% deuteration of the products with 25–100% stereoselectivity towards the α-carbon atom. These results, together with those of pH-static hydrogenation of complex 1 , suggest that water strongly assists the dehydrochlorination of 1 to yield the catalytically active monohydrido species HRh(PTA) 3 ( 2 ). Nevertheless, depending on the substrate and the pH of the solution the dihydridic pathway may remain partially operative.

Homogeneous hydrogenation of aqueous hydrogen carbonate to formate under mild conditions with water soluble rhodium(I)- and ruthenium(II)-phosphine catalysts

Water-soluble rhodium(I)- and ruthenium(II)tertiary phosphine complexes with meta-mono-sulphonated triphenylphosphine (TPPMS) and 1,3,5-triaza-7-phosphaadamantane (PTA) as ligands catalyze the hydrogenation of aqueous HCO3- to HCO2- under mild conditions. No amine additive is needed for good turnovers. CO2 accelerates the reactions with [RhCl(TPPMS)(3)] catalyst; however, it slightly inhibits the reductions catalyzed by [RuCl2(TPPMS)(2)]. Bicarbonate formed in the reaction of limestone with aqueous CO2 can also be used as starting material for formate production. Copyright (C) 2000 John Wiley & Sons, Ltd.

Aqueous organometallic catalysis. Isotope exchange reactions in H2–D2O and D2–H2O systems catalyzed by water-soluble Rh- and Ru-phosphine complexes

The water-soluble complexes [{RuCl2(mTPPMS)2}2], [RuCl2(PTA)4], [RhCl(mTPPMS)3], [RhCl(mTPPTS)3], and [RhCl(PTA)3] (mTPPMS = sodium salt of meta-sulfonatophenyl-diphenylphosphine, mTPPTS = sodium salt oftris(meta-sulfonatophenyl)phosphine, and PTA = 1,3,5-triaza-7-phosphaadamantane) showed high catalytic activity (up to 1252 h−1) in the H–D isotope exchange reactions between H2 and D2O or D2 and H2O. The reactions took place at 20–70 °C, 0.1–2 MPa H2, and were strongly influenced by the pH. In the hydrogenation (with H2) of unsaturated acids in D2O, the relative rates of H–D exchange, hydrogenation and deuteration were determined by the individual substrates and catalysts: in the reaction of maleic acid catalyzed by [RhCl(mTPPMS)3] only hydrogenation took place with no deuteration and H–D exchange, whereas a similar reaction of itaconic acid was accompanied by a fast H–D exchange and the product methylsuccinic acid was highly deuterated.

Catalytic hydrogenation and deuteration of phospholipid model membranes with a water-soluble chlorotris(1,3,5-triaza-7-phosphaadamantane)rhodium(I) complex catalyst

Abstract The water-soluble chlorotris(1,3,5-triaza-7-phosphaadamantane)rhodium(I), [RhCl(PTA) 3 ], was successfully employed for hydrogenation of phospholipid liposomes as model membranes in aqueous media under mild conditions. The highest conversion was achieved at pH 4.70. Formation of asymmetrically dideuterated lipids, together with isomerization and kinetic results revealed the important role of reversible formation of an alkyl-rhodium intermediate in the mechanism.

Homogeneous hydrogenation of aqueous hydrogen carbonate to formate under exceedingly mild conditions—a novel possibility of carbon dioxide activation†

Water soluble ruthenium(II)– and rhodium(I)–phosphine complexes catalyze the hydrogenation of aqueous HCO3– to HCO2– under mild conditions with turnover frequencies up to 262 TO h–1.

Colloidal metal dispersions as catalysts for selective surface hydrogenation of biomembranes. Part 2. Preparation of nanosize platinum metal catalysts and characterization in hydrogenation of water soluble olefins and synthetic biomembrane models

Abstract Aqueous dispersions of PVP-protected Pd, Pt, Rh, PdPt and PdRh colloids (PVP=poly(2-vinylpyrrolidone)) were successfully applied for the catalytic hydrogenation of water soluble olefins and liposomes as models of biological membranes. The metal-PVP particles were anchored onto the surface of water insoluble, crosslinked poly(2-vinylpyrrolidone), PVPP. Both the sols and the supported catalysts are stable in time, non-permeable to the lipid membrane, and can be separated completely from the reaction mixture by decantation or centrifugation.

H/D exchange between H2–D2O and D2–H2O catalyzed by water soluble tertiary phosphine complexes of ruthenium(II) and rhodium(I)

In aqueous solutions, [RuCl2(TPPMS)(2)](2) (TPPMS = 3-sulfonatophenyldiphenylphosphine) catalyzes the exchange between H-2 and D2O or between D-4 and H2O with high efficiency (up to 1 252 turnovers per hour) under mild conditions (298 K, 2 MPa H-2). The exchange rate strongly depends on the solution pH. Similar H/D exchange is observed with the water soluble tertiary phosphine complexes [RhCl(TPPMS)(3)], [RhCl(TPPTS)(3)] and [RuCl2(PTA)(4)] as catalysts (TPPTS = tris(3-sulfonatophenyl)phosphine. PTA = 1,3,5-triaza-7-phosphadamantane) which, however, show lower activity

Colloidal metal dispersions as catalysts for selective surface hydrogenation of biomembranes, 1. Preparation and characterization of palladium catalysts

Paliadium sols containing largely uniform, nanosize metallic, particles stabilized by poly(N-vinyl-2-pyrrolidone) were found to be active microheterogeneous catalysts for hydrogenation of water soluble olefinic substrates as well as of unsaturated lipid dispersions. The same metallic particles were supported on the surface of crosslinked insoluble poly(N-vinyl-2-pyrrolidone) and served as easily removable macroheterogeneous hydrogenation catalysts.

Modification of Biomembranes by Catalytic Hydrogenation

The integrity and function of biomembranes critically depends on their fluidity which in turn is largely, though not entirely, determined by the fatty acid composition of polar lipid constituents of the membrane. Heterogeneous catalytic hydrogenation has been widely used for modification the fatty acid composition of fats and oils. However only with the introduction of homogeneous catalysis did hydrogenation become a rather general, usefool tool of membrane biochemistry. Homogeneously catalyzed hydrogenation was applied for the study of the most widely differring organisms, from algae to human peripheric lymphocytes, from plant protoplasts to rat liver mitochondria and gave information on the most diverse membrane associated processes in isolated organelles or in living whole cells [1,2].