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Bimetallic Complex (bimetallic + complex)
Selected AbstractsBis(fluoromesityl) Palladium Complexes, Archetypes of Steric Crowding and Axial Protection by ortho Effect , Evidence for Dissociative Substitution Processes , Observation of 19F,19F Through-Space CouplingsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2004Camino Bartolomé Abstract Bisarylated complexes trans -[Pd(Fmes)2(SR2)2] [Fmes = 2,4,6-tris(trifluoromethyl)phenyl (fluoromesityl); SR2 = SMe2, tht; tht = tetrahydrothiophene] are precursors for various bisarylated fluoromesityl palladium(II) complexes by ligand-substitution reactions. Boiling under reflux in acetonitrile gives the mixed complexes trans -[Pd(Fmes)2(NCMe)(SR2)], whereas boiling under reflux in toluene leads to trans -[PdCl2L2] (L = PMe3, tBuNC, pTol-NC, 4-MePy), in the presence of neutral monodentate ligands, or to (NnBu4)[trans -Pd(Fmes)2I(SR2)] when treated with (NnBu4)I. trans -[Pd(Fmes)2(SMe2)2] reacts with bidentate ligands, also boiling under reflux in toluene, to give [Pd(Fmes)2(L,L)] [L,L = Me2bipy, 2,2, - biquinolyl, ,2N,N, -OCPy2, dppm (Ph2PCH2PPh2), dppe (Ph2PCH2CH2PPh2), pte (PhSCH2CH2SPh), ,2S,N -SPPh2Py, ,2O,N -OPPhPy2], or the bimetallic complex [Pd(Fmes)2(,-1,N:1,2,O:2,N -Py2MeCO)Pd(Fmes)(SMe2)] (characterized by X-ray diffractometry) when treated with (OH)(CH3)CPy2. The crowding associated with two Fmes groups produces several interesting features: (1) trans complexes are preferred over cis complexes, against the expected electronic preferences; (2) the low-temperature NMR spectra of several complexes, or the X-ray diffraction structure of [Pd(Fmes)2(2,2, - biquinolyl)], reveal significant structural distortions associated with steric crowding; (3) the need for boiling under reflux in the synthesis suggests a dissociative substitution mechanism, which is unknown so far for Pd; (4) some of the complexes show 19F,19F through-space couplings. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Polymerization of Methyl Acrylate by a 2,6-Bis(2-benzimidazyl)pyridine Zirconium Dichloride/MAO Catalyst SystemMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 21 2006Hyun Yong Cho Abstract Summary: A novel non-metallocene Zr(IV) complex bearing a bianionic form of the ligand 2,6-bis(2-benzimidazolyl)pyridine is synthesized. This Zr complex is an active catalyst for the polymerization of MA via coordination polymerization in the presence of methylaluminoxane MAO. The activity and MWD are increased as the polymerization temperature increases. The maximum activity is observed at Al/Zr molar ratio of 100 and the deactivation is shown above 100, resulting from an inactive bimetallic complex between catalyst and free TMA presented in MAO. Decrease in MWD is observed with higher MAO concentration due to its role in chain transfer during the chain propagation. The reaction of the ligand and catalyst synthesis. [source] Catalytic performance of chitosan-Schiff base supported Pd/Co bimetallic catalyst for acrylamide with phenyl halidePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 4 2010Wang Li-xia Abstract The chitosan-Schiff base supported palladium and cobalt bimetallic complex was synthesized in a simple method and characterized by Fourier-transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), and X-ray photoelectron spectra (XPS). It was found that the catalyst has great activity and stability in the coupling of acrylamide (AA) with the phenyl halide. The influence of various bimetallic catalysts, the different molar ratio of Co/Pd, the bases, the amount of the catalyst and base, and the molar ratio of iodobenzene/AA on the reaction were investigated. The results showed that the catalytic activity of the molar ratio of Co/Pd (3/1) was the best when the iodobenzene was used as a substrate. The yield of the cinnamamide did not change significantly after ten runs. It has been revealed that the catalyst was efficient for the reaction. Copyright © 2009 John Wiley & Sons, Ltd. [source] A pentanuclear bimetallic complex of manganese(II) and aluminium(III) ions: tetra-,2 -iodido-iodidobis(,3 -2-methoxyethanolato)bis(,2 -2-methoxyethanolato)dimethyl(tetrahydrofuran-,O)aluminium(III)tetramanganese(II)ACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2007Lucjan B. Jerzykiewicz The molecule of the title compound, [Mn4Al(CH3)2(C3H7O2)4I5(C4H8O)], contains one AlIII and four MnII ions. Two Mn atoms are five-coordinate in the form of a trigonal bipyramid or a square pyramid. The two other Mn atoms are six-coordinate with an octahedral geometry. The fourcoordinate Al atom is linked to the manganese core by ,-Oalkoxo bridges, forming an almost planar five-membered ring. [source] Cyclic Carbonate Synthesis Catalysed by Bimetallic Aluminium,Salen ComplexesCHEMISTRY - A EUROPEAN JOURNAL, Issue 23 2010William Clegg Prof. Abstract The development of bimetallic aluminium,salen complexes [{Al(salen)}2O] as catalysts for the synthesis of cyclic carbonates (including the commercially important ethylene and propylene carbonates) from a wide range of terminal epoxides in the presence of tetrabutylammonium bromide as a cocatalyst is reported. The bimetallic structure of one complex was confirmed by X-ray crystallography. The bimetallic complexes displayed exceptionally high catalytic activity and in the presence of tetrabutylammonium bromide could catalyse cyclic carbonate synthesis at atmospheric pressure and room temperature. Catalyst-reuse experiments demonstrated that one bimetallic complex was stable for over 60 reactions, though the tetrabutylammonium bromide decomposed in situ by a retro-Menschutkin reaction to form tributylamine and had to be regularly replaced. The mild reaction conditions allowed a full analysis of the reaction kinetics to be carried out and this showed that the reaction was first order in aluminium complex concentration, first order in epoxide concentration, first order in carbon dioxide concentration (except when used in excess) and unexpectedly second order in tetrabutylammonium bromide concentration. Further kinetic experiments demonstrated that the tributylamine formed in situ was involved in the catalysis and that addition of butyl bromide to reconvert the tributylamine into tetrabutylammonium bromide resulted in inhibition of the reaction. The reaction kinetics also indicated that no kinetic resolution of racemic epoxides was possible with this class of catalysts, even when the catalyst was derived from a chiral salen ligand. However, it was shown that if enantiomerically pure styrene oxide was used as substrate, then enantiomerically pure styrene carbonate was formed. On the basis of the kinetic and other experimental data, a catalytic cycle that explains why the bimetallic complexes display such high catalytic activity has been developed. [source] Mono-, Bi-, Tri- and Tetranuclear Palladium(II), Copper(I), and Gold(I) Complexes of Morpholine- and N -Methylpiperazine-Functionalized Cyclodiphosph(III)azans, cis -[(tBuN-,)2(PNC4H8X)2] (X = O, NMe)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 26 2010Maravanji S. Balakrishna Abstract Bis(amido)cyclodiphosphazanes, cis -[(tBuN-,)2(PNC4H8O)2] (2) and cis -[(tBuN-,)2(PNC4H8NMe)2] (3) were synthesized by treating the corresponding amines with cis -[ClP(tBuN-,)2PCl] (1). The stoichiometric reactions of 2 or 3 with elemental sulfur and selenium afforded the bis-chalcogenides, cis -[(tBuN-,)2(P(E)NC4H8X)2] (X = O, E = S; 4, X = NMe, E = S; 5, X = O, E = Se; 6, X = O, E = Se; 7). The reactions of 2 or 3 with [PdCl2(SMe2)2] produced exclusively the mononuclear trans -[PdCl2{(tBuN-,)2(PNC4H8X)2}2] (X = O; 8, X = NMe; 9), whereas the reactions with [Pd(,-Cl)(,3 -C3H5)]2 afforded the bimetallic complexes [{PdCl(,3 -C3H5)}2{(tBuN-,)2(PNC4H8X)2}] (X = O; 10, X = NMe; 11) in good yield. Treatment of 2 or 3 with [AuCl(SMe2)] in 1:1 and 1:2 molar ratios yielded the mono- and binuclear complexes, [{AuCl(tBuN-,)2(PNC4H8O)2}] (X = O; 12, X = NMe; 13), [{AuCl}2{(tBuN-,)2(PNC4H8O)2}] (X = O; 14, X = NMe; 15), respectively. The PdII (8) and AuI (12) complexes were used as metallo-ligands to prepare homo- and heterometallic complexes, trans -[PdCl2{(tBuN-,)2(PNC4H8O)2}2{Pd(,3 -C3H5)Cl}2] (16), trans -[PdCl2{(tBuN-,)2(PNC4H8O)2}2(AuCl)2] (17), and [Cu(CH3CN)(,-Cl)2Cu(CH3CN){(tBuN-,)2(PNC4H8O)2}2(AuI)2](18). The crystal structures of 2, 4, 7,9, 14, 15, and 18 were established by single-crystal X-ray diffraction studies. [source] Heterobimetallic Systems Containing Organometallic and Classical Coordination Sites: Effects of Subtle Changes in the Werner-Type SiteEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2005Tianlu Sheng Abstract Several highly unsymmetrical heterodinuclear Mn/Zn complexes are reported, in which an organometallic CpMn-(CO)2 fragment and a classical Werner-type zinc coordination unit are arranged in close proximity by means of a bridging pyrazolate. Ligand scaffolds differing in the chelate size of the tripodal tetradentate {N4} binding site, and different coligands for zinc are employed. Both the zinc-devoid precursor compounds and the bimetallic complexes with zinc(II) nested in the tris(pyridylalkyl)amine type {N4} compartment have been characterized by X-ray crystallography. Structural and spectroscopic features as well as the redox potentials of the MnI/MnII couple indicate slight effects of the redox-inactive Werner-type subunit on the properties of the organometallic site. Oxidation is highly localized at the organometallic manganese site, as is evidenced by IR and EPR spectroscopy and supported by DFT calculations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Tetraaqua-1,4O -bis(,-caprolactam-1,O)-,-cyano-1:2,2N:C -pentacyano-2,5C -iron(III)yttrium(III), a novel cyano-bridged dinuclear complexACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2002Yi He Using caprolactam as a ligand, the novel title cyano-bridged yttrium(III),ferricyanide complex, [Y(caprolactam)2(H2O)4Fe(CN)6] or [FeY(CN)6(C6H11NO)2(H2O)4], has been synthesized and structurally characterized. The Y atom is seven-coordinate and has approximately pentagonal,bipyramidal stereochemistry, with water molecules occupying apical positions. Of the five ligands in equatorial positions, one is the N -bound bridging cyano group, and flanking this are two O -bound caprolactam moieties, which are markedly inclined towards the bridged ferricyanide moiety such that they partially envelop it. Water molecules occupy the remaining two equatorial positions. The Y,N,C,Fe,C,N sequence of atoms lies on a crystallographic twofold axis and is therefore perfectly linear, which has not been observed previously in cyano-bridged bimetallic complexes. [source] Cyclic Carbonate Synthesis Catalysed by Bimetallic Aluminium,Salen ComplexesCHEMISTRY - A EUROPEAN JOURNAL, Issue 23 2010William Clegg Prof. Abstract The development of bimetallic aluminium,salen complexes [{Al(salen)}2O] as catalysts for the synthesis of cyclic carbonates (including the commercially important ethylene and propylene carbonates) from a wide range of terminal epoxides in the presence of tetrabutylammonium bromide as a cocatalyst is reported. The bimetallic structure of one complex was confirmed by X-ray crystallography. The bimetallic complexes displayed exceptionally high catalytic activity and in the presence of tetrabutylammonium bromide could catalyse cyclic carbonate synthesis at atmospheric pressure and room temperature. Catalyst-reuse experiments demonstrated that one bimetallic complex was stable for over 60 reactions, though the tetrabutylammonium bromide decomposed in situ by a retro-Menschutkin reaction to form tributylamine and had to be regularly replaced. The mild reaction conditions allowed a full analysis of the reaction kinetics to be carried out and this showed that the reaction was first order in aluminium complex concentration, first order in epoxide concentration, first order in carbon dioxide concentration (except when used in excess) and unexpectedly second order in tetrabutylammonium bromide concentration. Further kinetic experiments demonstrated that the tributylamine formed in situ was involved in the catalysis and that addition of butyl bromide to reconvert the tributylamine into tetrabutylammonium bromide resulted in inhibition of the reaction. The reaction kinetics also indicated that no kinetic resolution of racemic epoxides was possible with this class of catalysts, even when the catalyst was derived from a chiral salen ligand. However, it was shown that if enantiomerically pure styrene oxide was used as substrate, then enantiomerically pure styrene carbonate was formed. On the basis of the kinetic and other experimental data, a catalytic cycle that explains why the bimetallic complexes display such high catalytic activity has been developed. [source] Electronic and Magnetic Properties of Bimetallic Ytterbocene Complexes: The Impact of Bridging Ligand GeometryCHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2008Christin Abstract Bimetallic ytterbocene complexes with bridging N-heterocylic ligands have been studied extensively in recent years due to their potential applications ranging from molecular wires to single-molecule magnets. Herein, we review our recent results for a series of ytterbocene polypyridyl bimetallic complexes to highlight the versatility and tunability of these systems based on simple changes in bridging ligand geometry. Our work has involved structural, electrochemical, optical, and magnetic measurements with the goal of better understanding the electronic and magnetic communication between the two ytterbium metal centers in this new class of bimetallics. [source] | |||||||||||||