Reactivity differences between 2,4- and 2,5-disubstituted zirconacyclopentadienes: a highly selective and general approach to 2,4-disubstituted phospholes.

International audienceMixtures of 2,4- and 2,5-disubstituted zirconacyclopentadienes were obtained by the reductive dimerisation of terminal alkynes using the Cp2ZrCl2/lanthanum system. Reactions of dihalophosphines with these mixtures afforded selectively the corresponding 2,4-disubstituted phospholes and 1,4-disubstituted butadienes. A new series of phospholes was characterized by multi-nuclear NMR spectroscopy and X-ray analysis. A possible explanation for the observed selectivity was obtained from X-ray studies and DFT analysis of the intermediate zirconacyclopentadienes

Synthesis and characterisation of divalent di(1,3-bis(diphenylphosphano)cyclopentadienyl)lanthanoid and alkaline earth complexes as potential platforms for heterometallic complexes

New divalent lanthanoid and alkaline earth metal complexes bearing the 1,3-bis(diphenylphosphano)cyclopentadienyl ligand have been synthesised using the redox-transmetallation protolysis (RTP) approach. From the reaction of the corresponding metal, diphenylmercury and the proligand C5H4(PPh2)2, the compounds [M(η5-C5H3(PPh2)2-1,3)2(S)] (with M=Yb, S=(thf)2 or M=Yb, Eu, Ca, Sr, Ba, S=dme) were isolated and characterised by X-ray diffraction and multinuclear NMR spectroscopy. These compounds may provide a platform for early-late heterobimetallic complexes

Picking One out of Three: Selective Single C−F Activation in Trifluoromethyl Groups

International audienceThe introduction of a trifluoromethyl (CF3) group into an organic molecule can modify its chemical behavior and lead to changes in its physicochemical and pharmacological properties. The CF3 group is often chosen for its chemical inertness and stability, which are related to the strong C−F bonds. In recent years, the potential of gaining straightforward access to difluorinated compounds through selective single C−F activation in CF3 groups has been unveiled. This review describes the latest methodologies for the synthesis of difluoromethylated arenes, difluoroalkenes and difluorinated aldol products of potential synthetic and/or biological interest, employing low‐valent metals, transition metal catalysis, FLP and Lewis acid mediated transformations as well as photoredox catalysis

GECOM – CONCOORD 2006

7-12 Mai 200

Synthèse de complexes organophosphorés de lanthanides divalents et trivalents et leur application en catalyse.

Organo! lanthani de chemistry has long been dominated by cyclopentadienyl-based ligands whereas phosphorus-containing ligands have attracted interest only recently. In this work we show the influence of organophosphorus ligands on the synthesis and reactivity of organolanthanide compounds in three different areas. The first part is dedicated to the synthesis of "new" divalent organolanthanide complexes using both cyclopentadienyl and phospholyl based ligands. A new synthetic method - the reductive approach - is developed which allows the synthesis of base-free divalent thulocenes and unprecedented divalent dysprosium and neodymium ate-complexes. Small molecule activation with these new divalent compounds reveals their strong reducing nature and some differences between cyclopentadienyl- and phospholyl-containing complexes. The second part describes the synthesis of the first trivalent monophospholyl-bis(o-dimethylaminobenzyl)lanthanide complexes by classical salt-metathesis! reactions. In addition, a stable 1H phosphole is used for the first time in aLa chimie organométallique des lanthanides a été longtemps dominée par des ligands à base de cyclopentadiényle tandis que des ligands contenant du phosphore n'ont suscité de l'attention que récemment. Dans ce travail nous montrons l'influence de ligands organophosphorés sur la synthèse et la réactivité de composés organométalliques de lanthanides dans trois domaines différents. La première partie est dédiée à la synthèse de complexes divalents de lanthanides employant des ligands à base de cyclopentadiényle et de phospholyle. Une nouvelle méthode de synthèse – l'approche par réduction – est développée, qui permet la synthèse de thulocènes divalents ainsi que les premiers complexes divalents de dysprosium et de néodyme. L'activation de petites molécules montre la! nature fortement réductrice de ces complexes divalents et révèle quelques différences entre les composés à base de cyclopentadiényle et de phospholyle. La deuxième partie décrit la synthèse de premiers complexes monophospholyles bis(o-dimethylaminobenzyles) de lanthanides par métathèse. De plus, un phosphole 1H stable est utilisé pour la première fois comme précurseur dans une réaction de type acide base. L'application de ces composés dans la polymérisation du styrène est rapportée. La troisième partie s'intéresse à la synthèse et la réactivité de nouveaux complexes mono et bis(carbénique) de lanthanides utilisant le dianion 1,1-dilithio-bis(diphénylthiophosphinoyl)méthane comme précurseur carbénique. Une discussion sur la nature de la liaison Ln-C multiple par des analyses structurales ! et réactionnelles est incluse