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Accueil > Séminaires > Archive des séminaires d’Utinam > Archive des séminaires de chimie (jusqu’en 2011) > 2009

Mono- and Multidentate N-Heterocyclic Carbenes : Versatile Ligands for Organometallic Nucleophilic Catalyst

par Edith Burgey -

Mardi 2 juin 2009

Doris Kunz

Université de Heidelberg, Institut de Chimie Organique (Allemagne)

Résumé : N-heterocyclic carbenes (NHCs) are very versatile compounds that gained much interest and found applications as ligands for
organometallic complexes, as organic catalysts and also as precursors for the preparation of ionic liquids.
We have prepared and structurally characterized mono- and dipyrido annelated NHCs and used them as ligands for Rh- and Pd
catalyst, modifying the reactivity by steric modifications.
So called pincer-ligands are versatile ligands in coordination chemistry due to the general high stability of their complexes. Our
pincer-ligand containing two N-heterocyclic carbene moieties attached to a carbazolid backbone features strong electron donating
properties. Its Rh(I) carbonyl complex shows a highly nucleophilic character that we took advantage of as a catalyst in the allylic
alkylation of allyl carbonates We can show that the isomerisation process occurs via an intermolecular h1-allyl transfer rather than
an h3-allyl isomerization of the involved h1-allyl Rh(I) species.

To take advantage not only of the high stability of N-hetercyclic carbenes, but also of their imidazolium salts, we have synthesised a
strongly zwitterionic fulvene as an ideal precursor for the synthesis of higly polar imidazolium substituted metallocenes.