Ruthenium complexes [Ru(CO) 2 (PPh 3 ) 2 (O 2 CR) 2 ] -3a (R = CH 2 OCH 3 ), 3b (R = iPr), 3c (R = tBu), 3d (R = 2-c C 4 H 3 O), and 3e (R = Ph) -were synthesized by treatment of Ru(CO) 3 -(PPh 3 ) 2 with the corresponding carboxylic acids. The molecular structures of the newly synthesized complexes in the solid state are discussed. Compounds 3a-e were successfully applied as catalysts in the addition of carboxylic acids to propargylic alcohols to give the corresponding β-oxo esters in good to excellent yields even in air. The different carboxylate ligands do not have an influence on the productivities, because the carboxylates exchange rapidly under the applied [a]2939 reaction conditions, as was confirmed by 31 P{ 1 H} NMR spectroscopic studies. The addition of catalytic amounts of Na 2 CO 3 resulted in an increase in β-oxo ester formation. The reaction is tolerant to the use of versatile functional groups on the propargylic alcohols and carboxylic acids, revealing a broad substrate generality. In contrast to most other known catalytic systems, even sterically hindered substrates, including 2,4,6-trimethylbenzoic acid, 1,1-diphenylprop-2-yn-1-ol, or the biologically active steroid ethisterone, were successfully converted.

Ruthenium complexes with the formulae Ru(CO) 2 (PR 3 ) 2 (O 2 CPh) 2 [6a-h;R = n-Bu, p-MeO-C 6 H 4 , p-Me-C 6 H 4 ,P h, p-Cl-C 6 H 4 , m-Cl-C 6 H 4 , p-CF 3 -C 6 H 4 , m,m'-(CF 3 ) 2 C 6 H 3 ]w ere prepared by treatment of triruthenium dodecacarbonyl [Ru 3 (CO) 12 ]w ith the respective phosphine and benzoic acid or by the conversion of Ru(CO) 3 (PR 3 ) 2 (8e-h)w ith benzoic acid. During the preparation of 8,r uthenium hydride complexes of type Ru(CO)(PR 3 ) 3 (H) 2 (9g, h)c ould be isolated as side products. Them olecular structures of the newly synthesizedc omplexes in the solid state are discussed. Compounds 6a-h were found to be highly effective catalysts in the addition of carboxylic acids to propargylic alcohols to give valuable b-oxo esters.T he catalyst screening revealed ac onsiderably influence of the phosphine'se lectronicn ature on the resulting activities. Theb est performances were obtained with complexes 6g and 6h,f eaturing electron-withdrawing phosphine ligands.A dditionally,c atalyst 6g is very active in the conversion of sterically demanding substrates,l eading to ab road substrate scope.T he catalytic preparation of simple as wella sc hallenging substrates succeeds with catalyst 6g in yields that often exceed those of established literature systems.F urthermore,t he reactions can be carriedo ut with catalyst loadings down to 0.1 mol% andr eactiont emperatures down to 50 8 8C.

The ruthenium complexes [Ru(CO)2(P(p-C6H4-X)3)2(O2CPh)2] (1a, X = CF3; 1b, X = Cl; 1c, X = H; 1d, X = Me; 1e, X = OMe) were successfully applied in the regioselective Markovnikov addition of carboxylic acids to terminal alkynes, yielding valuable enol esters. Catalyst screening revealed a significant influence of phosphine's electronic nature on activity and selectivity. The highest activity was achieved with catalyst 1a, featuring the most electron-withdrawing phosphine ligand. Selectivity and activity could be further improved by the addition of catalytic amounts of AgOTf. Moreover, excellent selectivities with up to 99% of the Markovnikov product were achieved. The electronic influence of the substrates on the reaction rate was quantified by Hammett plots. By the use of electron-rich alkynes or highly acidic carboxylic acids, the reaction rate could be increased. Hence, the addition of highly acidic pentafluorobenzoic acid to electron-rich 4-methoxyphenylacetylene can even be carried out quantitatively at 25 °C within 4 h. Furthermore, a broad range of simple as well as electronically or sterically challenging substrates could be isolated in good to excellent yields with high regioselectivity and under mild reaction conditions (25-70 °C). The best reported activities and selectivities were obtained for the conversion of aromatic alkynes.

A general catalytic protocol for the -arylation of aryl ketones has been developed. It involves the use of a pre-formed,

An amperometric immunosensor based on a redox active ferrocenyl end-grafted PAMAM dendrimer provides highly sensitive detection of immunoglobulin, down to 2 ng mL−1.