Homogeneous Catalysis and Mechanisms in Water and Biphasic Media

After its discovery in the early 1980s and successful application on an industrial scale (Ruhrchemie/Rhone-Poulenc process) [...

Ruthenium(II)-Arene Complexes of the Water-Soluble Ligand CAP as Catalysts for Homogeneous Transfer Hydrogenations in Aqueous Phase

The neutral Ru(II) complex κP-[RuCl2(η6-p-cymene)(CAP)] (1), and the two ionic complexes κP-[RuCl(η6-p-cymene)(MeCN)(CAP)]PF6 (2) and κP-[RuCl(η6-p-cymene)(CAP)2]PF6 (3), containing the water-soluble phosphine 1,4,7-triaza-9-phosphatricyclo[5.3.2.1]tridecane (CAP), were tested as catalysts for homogeneous hydrogenation of benzylidene acetone, selectively producing the saturated ketone as product. The catalytic tests were carried out in aqueous phase under transfer hydrogenation conditions, at mild temperatures using sodium formate as hydrogen source. Complex 3, which showed the highest stability under the reaction conditions applied, was also tested for C=N bond reduction from selected cyclic imines. Preliminary NMR studies run under pseudo-catalytic conditions starting from 3 showed the formation of κP-[RuH(η6-p-cymene)(CAP)2]PF6 (4) as the pivotal species in catalysis

Oxidation of Thiophene Derivatives with H 2 O 2 in Acetonitrile Catalyzed by [Cp* 2 M 2 O 5 ] (M = Mo, W): A Kinetic Study

International audienceThe oxidation of benzothiophene (BT), dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (DMDBT) by H2O2 to the corresponding sulfoxides and sulfones has been studied under homogeneous conditions in MeCN with the compounds [Cp*2M2O5] (M = Mo (1), W (2)) as precatalysts. The W system is ca. 100 times more efficient than the Mo analogue, while the relative reactivity of the thiophene substrates is approximately DBT/DMDBT/BT ≈ 10/5/1. For all reactions rate constants for both steps (thiophene derivative to sulfoxide, k1; sulfoxide to sulfone, k2) were measured. While k1 ≈ k2 for DBT and DMDBT, k1 << k2 for BT, independent of catalyst. Activation parameters for the stepwise oxidations of thiophene derivative to sulfoxide (BT to BTO, ΔH⧧ = 11.4(5) kcal mol−1 and ΔS⧧ = –26.1(1.6) eu; DBT to DBTO, ΔH⧧ = 7.7(6) kcal mol−1 and ΔS⧧ = –33(2) eu) and sulfoxide to sulfone (BTO to BTO2, ΔH⧧ = 10.8(5) kcal mol−1 and ΔS⧧ = –21.8(1.6) eu; DBTO to DBTO2, ΔH⧧ = 10.3(9) kcal mol−1 and ΔS⧧ = –25(3) eu) were calculated from variable temperature studies using [Cp*2W2O5]. DFT calculations suggest that the greater reactivity of DBT relative to BT is not caused by ground-state effects but rather by a transition-state effect associated with the greater thermodynamic gain in DBT oxidation

PGSE NMR studies on RAPTA derivatives: Evidence for the formation of H-bonded dicationic species

The self-aggregation tendency of RAPTA complexes [Ru(η6-p- cymene)PTA(-R)Cl2]X, R = H (1BPh4 and IPF6) and Me (2BPh4 and 20Tf), and [Ru(η6-p-cymene)(PTA) 2Cl]X (3BPh4 and 3BF4)] in acetone-de was investigated by means of diffusion NMR spectroscopy. On increasing the concentration, the protonated species (1X) undergoes intercationic self-aggregation driven by hydrogen bonding that leads to the formation of 122+ dications and a small amount of 12X + ion triples. © 2008 American Chemical Society

New Class of Half-Sandwich Ruthenium(II) Arene Complexes Bearing the Water-Soluble CAP Ligand as an in Vitro Anticancer Agent

Ruthenium(II) arene complexes of 1,4,7-triaza-9-phosphatricyclo[5.3.2.1]tridecane (CAP) were obtained. Cytotoxicity studies against cancer cell lines reveal higher activity than the corresponding PTA analogues and, in comparison to the effects on noncancerous cells, the complexes are endowed with a reasonable degree of cancer cell selectivity