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Bellemin-Laponnaz S.,CNRS Institute of Genetics and of Molecular and Cellular Biology | Bellemin-Laponnaz S.,University of Strasbourg | Dagorne S.,CNRS Strasbourg Institute of Chemistry
Chemical Reviews

Early transition metal N-Heterocyclic carbenes (NHC) complexes in catalysis remain a field to be explored and developed taking advantage of the robustness/stability imparted to the resulting metal-based catalytically active components. Recent and promising reports on the use of early transition metal NHC complexes in homogeneous catalysis include, most notably, their ability to effectively mediate ketone hydrosilylation, olefin/cyclic esters polymerization, and olefin hydroamination reactions. Recent developments in carbene lithium compounds includevthe isolation and structural characterization of Li+ adductsvbearing abnormal NHCs. In related studies on anionic NHCs, Lavallo and co-workers visolated and characterized a number of Li salts of carborane-containing NHC anions starting from a formally monoanionic carborane N-functionalized imidazolium salt as the protio ligand. Other examples of lithium and potassium NHC compounds have been reported and typically include polydentate ligands incorporating a carbene ligand with an anionic functional group and variously functionalized monodentate NHC ligands. Source

Dagorne S.,CNRS Strasbourg Institute of Chemistry | Fliedel C.,New University of Lisbon
Topics in Organometallic Chemistry

This chapter highlights the most recent and representative results on the use of organoaluminum compounds in polymerization catalysis with a special emphasis on discrete Al-incorporating catalysts. The first part of this contribution summarizes recent and noteworthy developments on well-defined Al-based initiators for the controlled (and stereocontrolled) polymerization of various monomers including isobutene, styrene, epoxides, methyl methacrylate, cyclic esters, and cyclic carbonates. The second part discusses the latest significant advances on the synthesis and structural characterization of polynuclear organoaluminum/transition (and f-block) metal complexes relevant to Ziegler-Natta-type catalysis. Graphical Abstract: © Springer-Verlag Berlin Heidelberg 2012. Source

Loison A.,CNRS Strasbourg Institute of Chemistry

Laboratory experiments carried out under plausible prebiotic conditions (under conditions that might have occurred at primitive deep-sea hydrothermal vents) in water and involving constituents that occur in the vicinity of submarine hydrothermal vents (e.g., CO, H(2)S, NiS) have disclosed an iterative Ni-catalyzed pathway of C-C bond formation. This pathway leads from CO to various organic molecules that comprise, notably, thiols, alkylmono- and disulfides, carboxylic acids, and related thioesters containing up to four carbon atoms. Furthermore, similar experiments with organic compounds containing various functionalities, such as thiols, carboxylic acids, thioesters, and alcohols, gave clues to the mechanisms of this novel synthetic process in which reduced metal species, in particular Ni(0), appear to be the key catalysts. Moreover, the formation of aldehydes (and ketones) as labile intermediates via a hydroformylation-related process proved to be at the core of the chain elongation process. Since this process can potentially lead to organic compounds with any chain length, it could have played a significant role in the prebiotic formation of lipidic amphiphilic molecules such as fatty acids, potential precursors of membrane constituents. Source

Le Bideau F.,University Paris - Sud | Dagorne S.,CNRS Strasbourg Institute of Chemistry
Chemical Reviews

Access to functionalized steroids via metal-mediated homogeneous catalysis lies outside the scope of the present contribution, except when the corresponding discrete transition-metal-functionalized substituted steroids have been isolated. This area has already been comprehensively reviewed elsewhere. Owing to its availability in the cold series, rhenium was also used as a model for technetium in that context. Though the transposition to the radioactive series could not be achieved, this nevertheless allowed access to new species and provided information about their affinities for the studied receptors or their lipophilicities. Nevertheless, substituted cyclopentadienes typically exhibit a limited stability, and besides, their characterization is complicated by their existence as a mixture of isomers. In contrast, fulvenes are easier to synthesize and handle due to their better stability. Moreover, access to a wide variety of cyclopentadienyl metals may be achieved upon varying the reaction conditions and reagents involved. Source

Bianco A.,CNRS Strasbourg Institute of Chemistry
Angewandte Chemie - International Edition

Graphene is considered the future revolutionary material. For its development, it is of fundamental importance to evaluate the safety profile and the impact on health. Graphene is part of a bigger family which has been identified as the graphene family nanomaterials (GFNs). Clarifying the existence of multiple graphene forms allows better understanding the differences between the components and eventually correlating their biological effects to the physicochemical characteristics of each structure. Some invitro and invivo studies clearly showed no particular risks, while others have indicated that GFNs might become health hazards. This Minireview critically discusses the recent studies on the toxicity of GFNs to provide some perspective on the possible risks to their future development in materials and biomedical sciences. Two sides of the coin: Graphene is part of a bigger family identified as the graphene family nanomaterials (GFNs). For their development, it is important to evaluate the safety profiles and impacts on health. Some studies clearly show no particular risks exist and others indicate that GFNs might become health hazards. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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