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Süss-Fink, Georg

Nom
Süss-Fink, Georg
Affiliation principale
Fonction
Professeur ordinaire
Email
georg.suess-fink@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/385

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  • Publication
    Accès libre
    Water-Soluble Phenanthroline Complexes of Rhodium, Iridium and Ruthenium for the Regeneration of NADH in the Enzymatic Reduction of Ketones
    (2007)
    Canivet, Jérôme
    ;
    Süss-Fink, Georg 
    ;
    Štěpnička, Petr
    The nicotinamide coenzyme NADH, consumed in enantioselective reduction of ketones catalysed by alcohol dehydrogenases, needs to be regenerated in order to maintain enzymatic activity. We therefore studied the catalytic potential of the cationic complexes [(η5-C5Me5)Rh(N∩N)Cl]+ (1: N∩N = 1,10-phenanthroline; 2: N∩N = 5-nitro-1,10-phenanthroline; 3: N∩N = 5-amino-1,10-phenanthroline), [(η5-C5Me5)Ir(N∩N)Cl]+ (4: N∩N = 5-nitro-1,10-phenanthroline) and [(η6-C6Me6)Ru(N∩N)Cl]+ (5: N∩N = 5-nitro-1,10-phenanthroline), isolated as the water-soluble chloride salts, for transfer hydrogenation of NAD+ to give NADH in aqueous solution. The best results were obtained with rhodium complex 1, which gave catalytic turnover frequencies up to 2000 h-1 in aqueous solution at pH 7 and 60 °C with sodium formate as the hydrogen source. When this NADH-regenerating catalytic system is combined with NADH-dependent enzymes, it is possible to chemoenzymatically reduce prochiral ketones such as acetophenone or 4-phenylbutan-2-one with high enantioselectivity. Combination of horse liver alcohol dehydrogenase (HLADH) or alcohol dehydrogenase from Rhodococcus sp. (S-ADH) with 1/formate as the NADH-regenerating system resulted in ee values up to 98 %, depending on the nature of the substrate and the enzyme. In order to explain the different catalytic activities, the electrochemical behaviour of complexes 1-5 has been studied.
  • Publication
    Accès libre
    Water-Soluble Arene Ruthenium Complexes Containing a trans-1,2-Diaminocyclohexane Ligand as Enantioselective Transfer Hydrogenation Catalysts in Aqueous Solution
    (2005)
    Canivet, Jérôme
    ;
    Labat, Gael
    ;
    Stoeckli-Evans, Helen 
    ;
    Süss-Fink, Georg 
    The cationic chloro complexes [(arene)Ru(H2N∩NH2)Cl]+ (1: arene = C6H6; 2: arene = p-MeC6H4iPr; 3: arene = C6Me6) have been synthesised from the corresponding arene ruthenium dichloride dimers and enantiopure (R,R or S,S) trans-1,2-diaminocyclohexane (H2N∩NH2) and isolated as the chloride salts. The compounds are all water-soluble and, in the case of the hexamethylbenzene derivative 3, the aqua complex formed upon hydrolysis [(C6Me6)Ru(H2N∩NH2)OH2]2+ (4) could be isolated as the tetrafluoroborate salt. The molecular structures of 3 and 4 have been determined by single-crystal X-ray diffraction analyses of [(C6Me6)Ru(H2N∩NH2)Cl]Cl and [(C6Me6)Ru(H2N∩NH2)OH2][BF4]2. Treatment of [Ru2 (arene) 2Cl4] with the monotosylated trans-1,2-diaminocyclohexane derivative (TsHN∩NH2) does not yield the expected cationic complexes, analogous to 1-3 but the neutral deprotonated complexes [(arene)Ru(TsN∩NH2)Cl] (5: arene = C6H6; 6: arene = p-MeC6H4iPr; 7: arene = C6Me6; 8: arene = C6H5COOMe). Hydrolysis of the chloro complex 7 in aqueous solution gave, upon precipitation of silver chloride, the corresponding monocationic aqua complex [(C6Me6)Ru(TsHN∩NH2)(OH2)]+ (9) which was isolated and characterised as its tetrafluoroborate salt. The enantiopure complexes 1-9 have been employed as catalysts for the transfer hydrogenation of acetophenone in aqueous solution using sodium formate and water as a hydrogen source. The best results were obtained (60 °C) with 7, giving a catalytic turnover frequency of 43 h-1 and an enantiomeric excess of 93 %.