Partners and International Organizations
(English)
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A, B, HR, CZ, DK, FIN, F, D, GR, H, I, NL, N, PL, RO, SI, SK, E, S, CH, GB
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Abstract
(English)
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Catalytic hydrogenation reactions and the reduction of carbon dioxide/limestone into formic acid/formate in aqueous solution have been investigated using water soluble ruthenium(II)- and rhodium(I)-phosphine (meta-monosulphonated-triphenylphosphine, m-TPPMS; para-monosulphonated-triphenylphosphine, p-TPPMS; meta -trisulphonated-triphenylphosphine, TPPTS; and 1,3,5-triaza-7-phosphaadamantane, PTA) complexes as catalysts. Several new ruthenium- and rhodium-hydrides were identified and characterised in situ by high pressure FT-IR and medium pressure 31P and 1H NMR spectroscopy, and the mechanism of the hydrogenations were investigated. No amine additive is needed in aqueous CO2 reduction for good turnover numbers (up to 9600 h-1 TOF). H2 gas pressure in D2O led to an isotope equilibrium with these catalysts, the kinetics of H/D exchange was studied to get mechanistic information on the reduction. Hydrogenation of trans-cinnamaldehyde in aqueous-organic mixtures is catalyzed by [RuCl2(p-TPPMS)4] and is also strongly influenced by the pH of the aqueous phase due to the pH-dependent formation of the hydrides. In acidic solutions ( pH < 2) an exclusive C=C reduction while in alkaline solutions (pH > 6) a selective C=O hydrogenation was observed. New chloro- and hydrido-complexes of Ru(II) with p-TPPMS were prepared. The X-ray structure of the p-TPPMS revealed that it has a Tolman cone angle slightly smaller than that of PPh3.
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