Hervé Clavier

Percent buried volume for phosphine and N-heterocyclic carbene ligands: steric properties in organometallic chemistry.

Electronic and steric ligand effects both play major roles in organometallic chemistry and consequently in metal-mediated catalysis. Quantifying such parameters is of interest to better understand not only the parameters governing catalyst performance but also reaction mechanisms. Nowadays, ligand molecular architectures are becoming significantly more elaborate and existing models describing ligand sterics prove lacking. This review presents the development of a more general method to determine the steric parameter of organometallic ligands. Two case studies are presented: the tertiary phosphines and the N-heterocyclic carbenes.

Ring-closing metathesis in biphasic BMI·PF6 ionic liquid/toluene medium: a powerful recyclable and environmentally friendly process

Biphasic BMI[middle dot]PF(6)/toluene solvent is a remarkably suitable and clean medium for performing olefin metathesis with a new 2nd generation ionic liquid supported-ruthenium catalyst: high levels of recyclability and reusability combined with a high reactivity were obtained with a variety of di- or tri-substituted and/or oxygen-containing dienes, and very low residual ruthenium levels were detected (1 to 22 ppm) in the products.

Continuous flow homogeneous alkene metathesis with built-in catalyst separation

Continuous flow homogeneous alkene metathesis using a supported ionic liquid phase (SILP) catalyst with CO2 as a transport vector allows the self-metathesis of methyl oleate with only a slight loss of activity for at least 10 h; cross-metathesis of dimethyl maleate with methyl oleate ceases after 3 h, but the catalyst remains active for methyl oleate metathesis. The reasons for this unusual behaviour are explored and a practical system for the cross-metathesis of methyl oleate with dimethyl maleate, under batch conditions, is described.

The Influence of Phosphane Ligands on the Versatility of Ruthenium–Indenylidene Complexes in Metathesis

The aim of the present study is to develop readily available and stable pre-catalysts that could be easily prepared on large scale from simple starting materials. Based on the hypothesis that substitution of classical PCy(3) with phosphanes of varying electron-donating properties could be a straightforward manner to improve catalytic activity, a methodical study dealing with the effect of phosphane fine-tuning in ruthenium-indenylidene catalysts was performed. Challenged to establish how the electronic properties of para-substituted phosphane ligands translate into catalyst activity, the versatile behaviour of these new ruthenium-indenylidene complexes was investigated for a number of metathesis reactions.

Improving Grubbs' II type ruthenium catalysts by appropriately modifying the N-heterocyclic carbene ligand

The introduction of N-heterocyclic carbene ligands that incorporate correctly substituted naphthyl side chains leads to increased activity and stability in second generation ruthenium metathesis catalysts.

Highly Selective Cobalt-Mediated [6 + 2] Cycloaddition of Cycloheptatriene and Allenes

[6 + 2] Cycloadditions between cycloheptatrienes with allenes have been investigated. Cobalt salts were found to promote this transformation efficiently. Moreover, this reaction was found to be highly selective since only one regioisomer was obtained with an excellent E/Z-selectivity.

Building Indenylidene–Ruthenium Catalysts for Metathesis Transformations

Ruthenium-mediated olefin metathesis has emerged as an indispensable tool in organic synthesis for the formation carbon–carbon double bonds, attested by the large number of applications for natural product synthesis. Among the numerous catalysts developed to mediate olefin metathesis transformations, ruthenium–indenylidene complexes are robust and powerful pre-catalysts. The discovery of this catalyst category was slightly muddled due to a first mis-assignment of the compound structure. This report provides an overview of the synthetic routes for the construction of the indenylidene pattern in ruthenium complexes. The parameters relating to the indenylidene moiety construction will be discussed as well as the mechanism of this formation

Synthesis and Activity in Ring-Closing Metathesis of Phosphine and NHC-Containing Ruthenium–Indenylidene (Bis)Pyridine Complexes

The reactions of Cl-2-Ru-(3-phenylindenylidene) complexes with excess pyridine lead to new ruthenium (Ru)-based bis(pyridine) adducts in good yield. These thermally robust catalysts have been tested in ring-closing metathesis (RCM). In spite of promising initiation rates, only moderate to good activities have been observed in kinetic studies on several substrates.