Etude experimentale et théorique des intéractions non-covalentes en chimie organométallique : le concept d'hémichélation

The present manuscript will present a rational method of synthesis, characterization, determination of the electronic structure and dynamic behaviour of solution-persistent, and formally unsaturated binuclear Cr(0)-M complexes (with M= Pd(II), Pt(II) or Rh(I)). This new class of complexes constitutes rare examples of persistent coordinatively unsaturated 14-electrons complexes, whose cohesion stems essentially from a compensation of insufficient donor/acceptor Cr-M bonding by non-covalent interactions of preponderant attractive Coulombic nature. By taking advantage of the ambiphilic character of a heteroditopic ligand capable of chelating a metal centre through covalent and noncovalent bonds, truly coordination-unsaturated complexes can be synthesized in a manageable form. We propose to name “Hemichelation” the half-covalent/half noncovalent bonding-relationship between the ambiphilic heteroditopic ligand and the electron-unsaturated metallic centre.Ce manuscrit présente une méthodologie rationnelle de synthèse, caractérisation, détermination de la structure électronique et du comportement dynamique d’espèces bimétalliques électroniquement insaturées de type Cr(0)-M (avec M = Pd(II), Pt(II) ou Rh(I)). Ces nouvelles espèces constituent de rares exemples d’entités électro-insaturées à 14 électrons ayant la spécificité d’être persistantes en solution. Leur cohésion structurale provient essentiellement de la compensation d’un faible caractère de type donneur/accepteur entre les deux métaux par des interactions non-covalentes Coulombiennes. Nous montrons ainsi qu’en tirant profit du caractère ambiphile d’un ligand hétéroditopique capable de chélater un centre métallique par l’établissement d’une liaison covalente et d’une interaction non-covalente, de nouvelles espèces coordinativement insaturées peuvent être obtenues. Nous proposons d’appeler ce nouveau mode de chelation : « Hemichelation »

Unusual outcome of the thermolytic condensation of diazoarylmethanes with a [tricarbonyl(η6-2-p-tolyl)chromium]2-oxazolyl chelate of tetracarbonylrhenium

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μ-Carbonyl-bis(carbonyl{η 5 -[tricarbonyl(η 6 -2-methylindenyl)chromium(0)]rhodium(III)})( Rh — Rh )

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Hydrosilylation of carbonyl and carboxyl groups catalysed by Mn(i) complexes bearing triazole ligands

Manganese(i) complexes bearing triazole ligands are reported as catalysts for the hydrosilylation of carbonyl and carboxyl compounds. The desired reaction proceeds readily at 80 degrees C within 3 hours at catalyst loadings as low as 0.25 to 1 mol%. Hence, good to excellent yields of alcohols could be obtained for a wide range of substrates including ketones, esters, and carboxylic acids illustrating the versatility of the metal/ligand combination

Systematic ligand variation to modulate the electrochemical properties of iron and manganese complexes

A series of iron(+iii) and manganese(+ii) complexes based on the dpaq (R)-ligand system (dpaq = 2-[bis(pyridine-2-ylmethyl)]amino-N-quinolin-8-yl-acetamide) were investigated using cyclic voltammetry (CV) to elucidate how the electronic properties of the ligands influence the overpotential and catalytic current in the context of water oxidation catalysis. For the Fe-complexes an electron withdrawing NO2 or CF3 group attached to the 5-position of the quinoline unit increased the catalytic current, but only with a simultaneous increase of the overpotential. However, when a pyrene moiety was attached to the dipicolylamine unit of the ligand, the overpotential decreased with concomitant increase of the catalytic current. Although the manganese complexes showed no reversible formation of a molecular catalytically active species for water oxidation, the variations of the ligand scaffold affected largely the same trends in their electrochemical behavior

Effect of Enhanced Electron Withdrawal on the Cohesion of Cr-Pd Hemichelates

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