Search results for "GM"
showing 10 items of 28548 documents
Palladium-catalyzed amination of aryl dibromides with secondary amines: synthetic and mechanistic aspects
1999
Abstract Diaminobenzenes are obtained starting from m- and p-dibromobenzenes and secondary amines in the presence of Pd(dba)2/P(o-tolyl)3and sodium tert-butoxide in moderate to good yields. Reductive dehalogenation of aryl dibromides is a major side reaction under these conditions. The study of this reaction has shown that the formation of reductive dehalogenation products occurs according to two independent ways. The first one proceeds via the well-known β-hydride elimination from amido-coordinated palladium complexes. The second one involves the formation of hydrido palladium complexes from amino-coordinated derivatives. Although our results do not allow us to propose a detailed mechanist…
Ethene/norbornene copolymerization with (isodicyclopentadienyl)titanium complex-MAO catalyst
2007
Norbornene (NB) homopolymerization and ethene/NB copolymerizations with a silylene-bridged (isodicyclopentadienyl)(tert-butylamido)titanium dichloride-methylalumoxane (MAO) catalyst system were investigated. This catalytic system shows no efficiency towards NB homopolymerization but produces poly(ethene-co-norbornene)s. An increase in the initial NB feed content leads to a loss of copolymerization activity as well as NB copolymer incorporation. The structure of the isodicyclopentadienyl fragment (IsodiCp) has a strong limiting effect on comonomer incorporation possibilities.
A new hydrogen bonding motif involved in self-recognition in the solid state by functionalised macrocycles
2011
Self-recognition within the crystal lattices of three functionalised macrocycles results in the formation of arrays of remarkably similar hermaphroditic pairs of macrocycles. In the case of two of the macrocycles containing acylhydrazine substituents, a hitherto unknown recognition pattern is found in the interaction of the hydrazine moiety with crown-ether oxygen atoms.
On the Road to MM′X Polymers: Redox Properties of Heterometallic Ni···Pt Paddlewheel Complexes
2014
On the quest of heterometallic mixed-valence MM'X chains, we have prepared two stable discrete bimetallic compounds: the reduced (PPN)[ClNi(μ-OSCPh)4Pt] (PPN = bis(triphenylphosphine)iminium; OSCPh = benzothiocarboxylato) and the oxidized [(H2O)Ni(μ-OSCPh)4PtCl] species. The role of the aqua and chlorido axial ligands is crucial to facilitate oxidation of the {Ni(μ-OSCPh)4Pt} core. Experimental and theoretical analyses indicate that a NiPt-Cl/Cl-NiPt isomerization process occurs in the oxidized species. The electronic structure of the reduced system shows two unpaired electrons, one located in a d(x(2)-y(2)) orbital of the Ni(II) ion and a second in the antibonding d(z(2)-dz(2)) combination…
Soluble Heterometallic Coordination Polymers Based on a Bis-terpyridine-Functionalized Dioxocyclam Ligand
2010
Soluble homo- and heterometallic coordination polymers containing transition metal cations (Cu(2+), Fe(2+), Co(2+), and Ni(2+) ions) were prepared in a two-step procedure using a polytopic bis(terpyridine)dioxocyclam ligand 1H(2) (dioxocyclam = 1,4,8,11-tetraazacyclotetradecane-5,7-dione). These supramolecular systems incorporate two different metal complexes, the metal cations being located both between two terpyridine units and in the macrocyclic framework. The characterization of these soluble architectures was investigated by cyclic voltammetry, mass spectrometry, viscosimetry, and UV-vis absorption and electron paramagnetic resonance (EPR) spectroscopies. Our results clearly indicate t…
Structural, photophysical and magnetic properties of transition metal complexes based on the dipicolylamino-chloro-1,2,4,5-tetrazine ligand
2015
International audience; The ligand 3-chloro-6-dipicolylamino-1,2,4,5-tetrazine (Cl-TTZ-dipica) 1, prepared by the direct reaction between 3,6-dichloro-1,2,4,5-tetrazine and di(2-picolyl)-amine, afforded a series of four neutral transition metal complexes formulated as [Cl-TTZ-dipica-MCl2]2, with M = Zn(II), Cd(II), Mn(II) and Co(II), when reacted with the corresponding metal chlorides. The dinuclear structure of the isostructural complexes was disclosed by single crystal X-ray analysis, clearly indicating the formation of [MII–(μ-Cl)2MII] motifs and the involvement of the amino nitrogen atom in semi-coordination with the metal centers, thus leading to distorted octahedral coordination geome…
Towards the synthesis of substituted porphyrins by a pyridyl group bearing a reactive functionality
2010
Pyridyl-substituted porphyrins bearing a reactive functionality were prepared via Suzuki cross-coupling reactions and resulted in very good yields. These compounds are precursors of new porphyrin architectures able to coordinate two metals: one in the porphyrin core and the second around the pyridyl moiety. During the coupling reactions, a higher reactivity of a chloro picolyl group was evidenced compared to a bromo function on the same reacting molecule.
Supramolecular chemistry of metalloporphyrins
2009
International audience
Versatile behavior of conjugated diynes with zirconocene reactive species
2008
Thermal decomposition of Cp2ZrPh2 in the presence of the buta-1,3-diynes RC≡CC≡CR (R = Ph, SiMe3) can lead to seven- or five-membered metallacycles. In both cases a stable benzo-fused seven-membered zirconacyclocumulene arising from a 2-fold insertion of the triple bonds of the dialkyne in the in situ generated zirconocene benzyne is formed. In the case of Me3SiC≡CC≡CSiMe3 a second minor complex is isolated: a 3-alkynyl-substituted zirconaindene arising from a β monoinsertion of one acetylenic function of the conjugated diyne in the zirconocene benzyne. No stable 2-alkynyl-substituted zirconacycle was isolated. This α monoinsertion complex is an intermediate in the exchange of the metalated…
Insight into the Mechanism of Water Adsorption/Desorption in Hydrophilic Viologen-Carboxylate Based PCP
2017
A water stable and highly hydrophilic porous coordination polymer based on viologen-carboxylate type ligand, the 4,4′-bipyridinium,1,1-bis(3-carboxyphenyl) (pc2), is obtained by the solvothermal method: [Cd3(pc2) (BTC)2(H2O)2]·6H2O ([1(H2O)2]·6H2O; BTC3– = 1,3,5-carboxybenzene). Its crystal structure and the ones of two partially dehydrated phases have been determined, allowing insight into the mechanism of water adsorption/desorption of this PCP material. It is shown that the dehydrated compound [1] first adsorbs two water molecules which fill the pores, leading to [1]·2H2O. On the other hand, the partial dehydration of the as-synthesized compound leads to the intermediate phase [1(H2O)]·3…