Evaluation de l'impact de Caulerpa racemosa sur les communautés benthiques coralligènes du Parc national de Port-Cros : les peuplements patrimoniaux de Cystoseira spp. et de Corallinacea.

Rapport scientifiqueEvaluation de l'impact de Caulerpa racemosa sur les communautés benthiques coralligènes du Parc national de Port-Cros : les peuplements patrimoniaux de Cystoseira spp. et de Corallinacea

Promoting Role of [PtI2(CO)]2 in the Iridium-Catalyzed Methanol Carbonylation to Acetic Acid and Its Interaction with Involved Iridium Species

The catalytic activity of the iridium complexes involved in methanol carbonylation is significantly enhanced when the carbonyliodoplatinum dimer [PtI2(CO)]2 (10') is added to the reaction mixt. Under CO this complex readily affords the monomeric species [PtI2(CO)2] (10). The turnover frequency value, which is 1450 h-1 for iridium alone, reaches 2400 h-1 for a Pt/Ir = 3/7 molar ratio, under 30 bar of CO and at 190°C. To get a deeper insight into the role of the platinum cocatalyst, model conditions (dinitrogen, ambient temp., CH2Cl2, PPN+ as counterion) have been adopted. [PtI2(CO)]2 (10') interacts with [PPN][IrI3(CH3)(CO)2] (4-PPN), affording the monoiodo-bridged anionic species [IrI2(CH3)(CO)2(μ-I)PtI2(CO)]- (11), which undergoes cleavage under CO to provide [IrI2(CH3)(CO)3] (6) and [PtI3(CO)]- (9). Although we have to take into account the possible iodide dissocn. from 4 in the polar reaction medium (CH3COOH, CH3OH, CH3I, HI, H2O), which can be scavenged by platinum to give 9, we should not discard the intermediacy of 11, even under working catalytic conditions. The crystal structures of [PPN][IrI3(COCH3)(CO)2] (8-PPN) and [PPN][PtI3(CO)] (9-PPN), which are both involved in the overall process, were detd. by X-ray diffraction anal. A catalytic cycle is herein proposed, in which the cooperative effect between the platinum promoter and the iridium catalyst is depicted

Tracing sewage and natural freshwater input in a Northwest Mediterranean bay: Evidence obtained from isotopic ratios in marine organisms

Elemental carbon and nitrogen levels and isotope ratios were assessed in different biological compartments of a Northwest (NW) Mediterranean bay to trace the various sources of nutrient input from natural (river runoffs) and anthropogenic (harbor outflows, fish farms and urban sewage outfall) sources. Samples from transplanted mussels and natural sea grass communities (Posidonia oceanica leaves and epiphytes) were harvested from different locations throughout the bay during the touristic summer and rainy seasons. The results from the nitrogen analysis revealed that sewage and harbor outflow promote higher nitrogen levels, enrichment of N-15 in the tissues, and a higher seasonal variability in sea grass and epiphytes. In mussel tissues, the delta N-15 was also influenced by sewage and harbor outflow, whereas delta C-13 was influenced by terrestrial inputs. These results suggest that natural and anthropogenic nutrient inputs have a temporary and localized influence and affect the sensitivity of natural isotopic ratios to changes in hydrologic conditions, especially to rain and tourism. (C) 2010 Elsevier Ltd. All rights reserved

Direct Involvement of the Acetato Ligand in the Reductive Elimination Step of Rhodium-Catalyzed Methanol Carbonylation

For the last step of rhodium-catalyzed methanol carbonylation, high-pressure NMR, and kinetic and experimental data supported by density functional theory calculations are consistent with substitution of I^– by an AcO^– ligand on the [RhI₃(COCH₃)­(CO)₂]⁻ species followed by reductive elimination of acetic anhydride, which immediately reacts with water to afford acetic acid