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Chelating Ligand (chelating + ligand)
Selected AbstractsAluminium Complexes of a Phenoxyimine Ligand with a Pendant Imidazolium Moiety: Synthesis, Characterisation and Evidence for Hydrogen Bonding in SolutionEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 35 2008Stefano Milione Abstract Novel alkylaluminium complexes (phim)AlMe2 (1) and(phimid)AlR2+Br, [R = Me (2), R = iBu (3)] bearing the Schiff base ligands 3,5- tBu2 -2-(OH)C6H2CH=NiPr (phim -H) and3,5- tBu2 -2-(OH)C6H2CH=NCH2CH2[CH(NCHCHNiPr)]Br(phimid -H·Br) have been prepared and fully characterised. Complexes 1,3 each have a tetrahedral structure, with the aluminium atom surrounded by the oxygen and nitrogen atoms of the chelating ligand and two alkyl groups. The structures of phimid -H·Br and of complex 1 have been determined by X-ray diffraction studies. Investigation of the solution structures of 1,3 by 1H NMR spectroscopy revealed that the coordinated phimid ligand is involved in hydrogen bonding with bromide anion. Treatment of 1 with B(C6F5)3 led smoothly to (phim)Al(C6F5)Me (4) by transfer of a C6F5 group from MeB(C6F5)3, to the initially formed coordinatively unsaturated cationic intermediate. In contrast, treatment of 2 with one equiv. of B(C6F5)3 afforded the cationic monomethyl species (phimid)AlMeBr+,MeB(C6F5)3, (5), stabilised by the coordination of the bromide anion acting as a Lewis base.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] New Coordination Modes of L -Ascorbic Acid and Dehydro- L -ascorbic Acid as Dianionic Chelating Ligand for PlatinumEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2008Paola Bergamini Abstract A variety of coordination modes of L -ascorbic acid as an anionic bidentate ligand has been exploited to prepare platinum(II) complexes 1,7 that contain phosphanes or R,R -dach (1R,2R -diaminocyclohexane) as neutral ligands in which O2, O3, O5, O6 and C2 act as anionic donating functionalities. An alternative synthetic route to known O2,O3 complexes is proposed, and their solubility in water has been enhanced by introducing PTA (1,3,5-triaza-7-phosphaadamantane) as a neutral ligand. A new coordination mode of ascorbic acid (O2 and O3 protected) as an O5,O6-diolate chelating ligand has been characterised in solution by NMR spectroscopy and in the solid state by X-ray crystallography. The first example of a platinum complex that contains dehydroascorbic acid, 7, has also been prepared and its X-ray crystal structure has been determined. The antiproliferative activity in vitro of complexes 1,7 has been tested, and the best values were obtained for the DHA complex 7, which was found to be more active than cisplatin on both a cisplatin-sensitive and a cisplatin-resistant cell line.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Tagging (Arene)ruthenium(II) Anticancer Complexes with Fluorescent LabelsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2007Fabio Zobi Abstract Fluorescent (arene)ruthenium(II) complexes have been prepared by tagging a small fluorogenic reporter onto the chelating ligand of complexes of the type [(,6 -arene)RuCl(Z)]+ (Z = chelating ligand). Complexes [(,6 - p -cym)RuCl(NNO)](Cl) (2), [(,6 - p -cym)RuCl(L3)](Cl) (3) and [(,6 - p -cym)RuCl(L4)](Cl) (4) {p -cym = p- cymene, NNO = 2-[(2-aminoethyl)amino]ethanol, L3 = 2-[(2-aminoethyl)amino]ethyl-2-(methylamino)benzoate and L4 = N -{2-[(2-aminoethyl)amino]ethyl}-2-(methylamino)benzamide} were obtained in good yield from the reaction of the Ru dimer [(,6 - p -cym)RuCl2]2 (1) and the corresponding ligand. The compounds have been fully characterized and their X-ray crystal structures are reported. Compounds 3 and 4 show a photoluminescence response centered at 435 nm with partial fluorescence quenching of the fluorogenic reporters L3 and L4 upon coordination to the metal center. Species 2,4 show good solubility both in water and organic solvents. In water, 2,4 readily hydrolyze to form the aqua complexes. These are stable at acidic pH forming 10,15,% of the corresponding hydroxido complexes in buffered solution (25 mM HEPES) as the pH is raised to a physiological value (pH = 7.44). Under these conditions, 4 (but not 2 or 3) undergoes a fast pH-dependent reversible intramolecular rearrangement. Experimental data and semiempirical calculations indicate that the major species arising from this transformation is a complex with a tridentate chelating ligand following deprotonation at the nitrogen atom of the amide group. Esterase-catalyzed hydrolysis of 3 liberates isatoic acid (MIAH) and generates 2 indicating that the complex is a substrate for the enzyme. Complexes similar to 3 may have potential for esterase-activated Ru-based prodrug delivery systems.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Coordination Chemistry of 3-Mercapto-2-(mercaptomethyl)propanoic Acid (Dihydroasparagusic Acid) with Iron and NickelEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2006Phillip I. Volkers Abstract The first transition-metal complexes bearing the natural product dihydroasparagusic acid, (HSCH2)2CHCO2H, as a ligand are reported. Various coordination modes and nuclearities are demonstrated for the chelating ligand by a series of iron and nickel complexes. Fe2[(SCH2)2CHCO2H](CO)6 retains carbonyl substitution reactivity typical of Fe2(SR)2(CO)6 complexes, yet carboxy coordination to FeI was unobserved. Coupling of the carboxylic acid with amines yields the corresponding amides Fe2[(SCH2)2CHC(O)NHR](CO)6 (R = Et, gly,O,tBu). Fe2[(SCH2)2CHCO2H](CO)4(PMe3)2 catalyzes H2 production, but no better than unfunctionalized alkyl dithiolate analogs. Reactions of the ligand with NiCl2(dppe) afforded mono-, di-, and trinuclear complexes. Noteworthy is Ni3[(SCH2)2CHCO2]2(dppe)2, which features an octahedrally coordinated NiII center linked to a pair of square-planar NiII centers. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Tris(tropolonato)phenanthroline Lanthanide(III) Complexes as Photochemical DevicesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2006Laura Bertolo Abstract The tris-tropolonato erbium(III) complexes [Er(hino)3(phen)] and [{Er(hino)3}2(pdon)] (H-hino = 2-hydroxy-6-isopropylcyclohepta-2,4,6-trien-1-one; phen = 1,10-phenanthroline; pdon = 1,10-phenanthroline-5,6-dione) have been prepared by reaction of [Er(hino)3]n with the appropriate chelating ligand in alcoholic solution. The complexes were characterized by elemental analyses, TG, ESI MS, 1H NMR, and IR spectroscopy, also by comparison with the properties of the analogous EuIII and YbIII complexes. The ESI-MS spectroscopy of the complex with the ditopic ligand pdon parallels the other physico-chemical data (IR, NMR), confirming the occurrence of a dinuclear entity. All the investigated ErIII complexes show efficient NIR emissions at about 1550 nm upon excitation at 355 nm in the UV ligand absorption band, emerging as possible candidate as active material for the realization of plastic amplifiers for telecommunications. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Synthesis, Structure and Spectroscopic Properties of Novel9,10-Bis{[6-(diphenylphosphanyl)-2-pyridylmethyl]propylaminomethyl}anthracene-Bridged Group 11 Metal (M = CuI and AgI) Dinuclear ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2005Hu Xu Abstract Dinuclear complexes [M2(,-BPNNAn)]X2 (M = CuI, X = ClO4,1, X = BF4,2; M = AgI, X = BF4,3, X = ClO4,4) have been prepared by treating 9,10-bis{[6-(diphenylphosphanyl)-2-pyridylmethyl]propylaminomethyl}anthracene (BPNNAn) with M(CH3CN)4X in CH2Cl2. The structures of complexes 1, 2 and 3 have been determined by single-crystal X-ray diffraction studies. In the complexes, BPNNAn acts as a chelating ligand and two metal ions riding on two bridgehead carbon atoms in the anthracene group leads to the deformation of the anthracenyl ring. The Cu,Arene charge transfer interaction is observed from the nonfluorescent emission of Cu complex 1, while the Ag complex 3 exhibits dual emission at high concentrations in a CH2Cl2 solution. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Palladium-Catalyzed One-Pot Conversion of Aldehydes to AmidesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2-3 2010Md Ashif Ali Abstract The palladium-catalyzed one-pot conversion of aldehydes into primary amides in the presence of hydroxylamine hydrochloride in aqueous dimethyl sulfoxide (DMSO) at moderate temperature is described. The process is selective and free from the addition of an external chelating ligand. [source] Hydrolysis of C,N -chelated diorganotin(IV) chlorides and catalysis of transesterification reactionsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 7 2009ka Pad, lková Abstract Diorganotin(IV) dichlorides of formula LCNRSnCl2 (where R is nBu or Ph) containing one LCN chelating ligand were hydrolyzed with aqueous sodium hydroxide in benzene. The composition of the products is strongly dependent on the amount of hydroxide. The partially hydrolyzed compounds of composition (LCNRSnCl)2(µ-O) were isolated as crystalline products. A hydrolysis where more than one molar equivalent of NaOH is employed gave only a mixture of unidentifiable products. The structure of (LCNPhSnCl)2(µ-O) was determined by X-ray diffraction techniques in the solid state. In solution there was a mixture of diastereoisomers found, where the tin atoms serve as a stereogenic centers. The catalytic activity of starting dichlorides as well as (LCNPhSnCl)2(µ-O) in various transesterification processes was investigated. The activity is very low in the case of starting dichlorides. When two molar equivalents of NaH are added or (LCNPhSnCl)2(µ-O) is employed in the catalytic experiments, the activity is comparable to the literature data. Copyright © 2009 John Wiley & Sons, Ltd. [source] Aluminum(III) complexes containing O,O chelating ligandAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 8 2007Libor Dostál Abstract The stoichiometric reactions of trimethylaluminum with 2,6-(MeOCH2)2C6H3OH (LH) revealed compounds L3Al (1) and L2AlMe (2). On the other hand reaction of 1 equiv. of LH with trimethylaluminum did not lead to the formation of complex LAlMe2 (3), rather 2 together with Me3Al were observed as a result of a disproportionation of 3. Compounds 1 and 2 were characterized by elemental analysis, 1H and 13C NMR spectroscopy and in the case of 1 by X-ray diffraction. Derivative 2 underwent transmetalation with Ph3SnOH, giving LSnPh3 (4) as the result of a migration of ligand L from the aluminum to the tin atom. The identity of 4 was established by elemental analysis, 1H, 13C and 119Sn NMR spectroscopy and 1H, 119Sn HMBC experiments. The system 2 and B(C6F5)3 in a 1:1 molar ratio was shown to be active in the polymerization of propylene oxide and ,-caprolactone. Copyright © 2007 John Wiley & Sons, Ltd. [source] Immobilized Metal Affinity Chromatography without Chelating Ligands: Purification of Soybean Trypsin Inhibitor on Zinc Alginate BeadsBIOTECHNOLOGY PROGRESS, Issue 1 2002Munishwar N. Gupta Immobilized metal affinity chromatography (IMAC) is a widely used technique for bioseparation of proteins in general and recombinant proteins with polyhistidine fusion tags in particular. An expensive and critical step in this process is coupling of a chelating ligand to the chromatographic matrix. This chelating ligand coordinates metal ions such as Cu2+, Zn2+, and Ni2+, which in turn bind proteins. The toxicity of chemicals required for coupling and their slow release during the separation process are of considerable concern. This is an important issue in the context of purification of proteins/enzymes which are used in food processing or pharmaceutical purposes. In this work, a simpler IMAC design is described which should lead to a paradigm shift in the application of IMAC in separation. It is shown that zinc alginate beads (formed by chelating alginate with Zn2+ directly) can be used for IMAC. As "proof of concept", soybean trypsin inhibitor was purified 18-fold from its crude extract with 90% recovery of biological activity. The dynamic binding capacity of the packed bed was 3919 U mL -1, as determined by frontal analysis. The media could be regenerated with 8 M urea and reused five times without any appreciable loss in its binding capacity. [source] Preparation of Immobilized Metal Affinity Chromatographic Packings by Immobilization of Carboxymethylated Asparate (CM-Asp) Based on Monodisperse Hydrophilic Non-porous Beads and Their ApplicationCHINESE JOURNAL OF CHEMISTRY, Issue 7 2010Bolin Gong Abstract The hydrophilic immobilized metal affinity chromatographic packing was prepared by immobilization of carboxymethylated asparate (CM-Asp) as chelating ligand and Ni2+ as center ion on the base of monodispersed, 3.0 µm non-porous monodisperse poly(glycidylmethacrylate- co -ethylenedimethacrylate) (PGMA/EDMA) particles. The retention behavior of proteins and the effect of pH on the retention in the range from 4.0 to 9.0 were investigated on both the naked and metal ion chelated columns. Four proteins were quickly separated in 2.0 min with linear gradient elution at a flow rate of 3.0 mL·min,1 by using the synthesized Ni2+ -CM-Asp-PGMA/EDMA packings. The separation time was shorter than other immobilized metal affinity chromatography reported in the literature. The Ni2+ -CM-Asp-PGMA/EDMA column was further investigated for the rapid separation and purification of copper-zinc superoxide dismutase (Cu,Zn-SOD) from the blood of pig in 3.0 min with only one step. The results obtained were satisfactory. [source] Synthesis and Luminescent Properties of Novel Europium(III) Heterocyclic ,-Diketone Complexes with Lewis Bases: Structural Analysis Using the Sparkle/AM1 ModelEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2005Rani Pavithran Abstract Tris(,-diketonato)europium(III) complexes of general formula [Eu(TPI)3·L], with chelating ligands such as 3-phenyl-4-(4-toluoyl)-5-isoxazolone (HTPI) and adduct-forming reagents [L = H2O, tri- n -octylphosphane oxide (TOPO), triphenylphosphane oxide (TPhPO), 1,10-phenanthroline], have been synthesized and characterized by elemental analysis and FT-IR, 1H NMR, and photoluminescence spectroscopy. The coordination geometries of the complexes were calculated using the Sparkle/AM1 (Sparkle model for the calculation of lanthanide complexes within the Austin model 1) model. The ligand,Eu3+ energy-transfer rates were calculated using a model of intramolecular energy transfer in lanthanide coordination complexes reported in the literature. The room-temperature PL spectra of the europium(III) complexes are composed of the typical Eu3+ red emission, assigned to transitions between the first excited state (5D0) and the multiplet (7F0,4). The results clearly show that the substitution of water molecules by TOPO leads to greatly enhanced quantum yields (i.e., 1.3,% vs. 49.5,%) and longer 5D0 lifetimes (220 vs. 980 ,s). This can be ascribed to a more efficient ligand-to-metal energy transfer and a less efficient nonradiative 5D0 relaxation process. The theoretical quantum yields are in good agreement with the experimental quantum yields, which highlights that the present theoretical approach can be a powerful tool for the a priori design of highly luminescent lanthanide complexes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Synthesis and Molecular Structures of Nickel(II) and Cobalt(III) Complexes with 2-(Arylimino)-3-(hydroxyimino)butaneEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2003Ennio Zangrando Abstract We report new series of NiII and CoIII complexes with nitrogen-donor chelating ligands of the (E,E)-2-(arylimino)-3-(hydroxyimino)butane type (Ar,N,N,OH). These ligands are characterized by a hydrophilic (OH group) and a hydrophobic region (aryl group). NiII derivatives were obtained either as trimers of formula [Ni3(Ar,N,N,OH)3Br4(OH)][Br], with the hydrophobic groups oriented on the same side, or as bis(chelated) derivatives with cis geometry, depending on the steric hindrance of the aryl groups. CoIII complexes were obtained only as bis(chelated) derivatives, with the two ligands coplanar. The "iso -oriented" arrangement of ligands in bis(chelated) CoIII complexes is favored by weak interactions between the two ligands, namely O,H···O hydrogen bond and stacking interactions between the aryl groups. CoIII complexes might find application as catalysts for living or controlled radical polymerization of polar olefins, and preliminary results are reported. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Silica-Supported Zirconium Complexes and their Polyoligosilsesquioxane Analogues in the Transesterification of Acrylates: Part 1.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2009Characterization, Synthesis Abstract Various silica-supported acetylacetonate and alkoxy zirconium(IV) complexes have been prepared and characterized by quantitative chemical measurements of the surface reaction products, quantitative surface microanalysis of the surface complexes, in situ infrared spectroscopy, CP-MAS 13C,NMR spectroscopy and EXAFS. The complex (SiO)Zr(acac)3 (acac=acetylacetonate ligand) (1) can be obtained by reaction of zirconium tetraacetylacetonate [Zr(acac)4] with a silica surface previously dehydroxylated at 500,°C. The complexes (SiO)3Zr(acac) (2) and (SiO)3Zr(O- n- Bu) (n- Bu=butyl ligand) (3) can be synthesized by reaction of (SiO)3ZrH with, respectively, acetylacetone and n -butanol at room temperature. The spectroscopic data, including EXAFS spectroscopy, confirm that in compound 1 the zirconium is linked to the surface by only one SiOZr bond whereas in the case of compounds 2 and 3 the zirconium is linked to 3 surface oxygen atoms which are sigma bonded. EXAFS data indicate also that the acetylacetonate ligands behave as chelating ligands leading to a hepta-coordination around the zirconium atom in 1 and a penta-coordination in 2. In order to provide a molecular analogue of 1, the synthesis of the following polyoligosilsesquioxane derivative (c -C5H9)7Si8O12(CH3)2Zr(acac)3 (1,) was achieved. The compound 1, is obtained by reacting (c -C5H9)7Si8O11(CH3)2(OH), 4, with an equimolecular amount of Zr(acac)4. In the same manner, syntheses of complexes (c -C5H9)7Si7O12Zr(acac) (2,) and of (c-C5H9)7Si7O12Zr(O- n- Bu) (3,) were achieved by reaction of the unmodified trisilanol, (c -C5H9)7Si7O9(OH)3, with respectively Zr(acac)4 and Zr(O- n- Bu)4 at 60,°C in tetrahydrofuran. Compounds 1,, 2, and 3, can be considered as good models of 1, 2 and 3 since their spectroscopic properties are comparable with those of the surface complexes. The synthetic results obtained will permit us to study the catalytic properties of these surface complexes and of their molecular analogues with the ultimate goal of delineating clear structure-activity relationships. [source] Osmium-Catalyzed Olefin Dihydroxylation and Aminohydroxylation in the Second Catalytic CycleADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2006Peng Wu Abstract Two catalytic cycles operate in the osmium-catalyzed olefin dihydroxylation and aminohydroxylation. Slow hydrolysis of the Os(VI) monoglycolate (or monoazaglycolate in aminohydroxylation) intermediate often results in the addition of another molecule of olefin thereby shunting the catalysis into the second catalytic cycle. As a result, both enantio- and chemoselectivity are reduced. A series of new chelating ligands were devised, which force the catalysis into the second cycle while maintaining enantiocontrol in the olefin addition step. Excellent catalytic turnover and moderate to good enantioselectivity were achieved. [source] Water-elutability of nucleic acids from metal-chelate affinity adsorbents: enhancement by control of surface charge density,JOURNAL OF MOLECULAR RECOGNITION, Issue 4 2006Joseph Y. Fu Abstract Immobilized metal affinity chromatography (IMAC) is widely used for purification of proteins, especially "hexahistidine-tagged" recombinant proteins. We previously demonstrated the application of IMAC to selective capture of nucleic acids, including RNA, selectively-denatured genomic DNA, and PCR primers through interactions with purine bases exposed in single-stranded regions. We also found that the binding affinity of nucleic acids for IMAC adsorbents can be increased several-fold by addition of 20 volume% of neutral additives such as ethanol or DMSO. In the present work, it is demonstrated that bound nucleic acids can be effectively eluted with water instead of the usual imidazole-containing competitive eluants, when the surface density of negative charges is enhanced by operation at alkaline pH, or by deliberate metal-underloading of the anionic chelating ligands. With enhanced negative surface charge density, nucleic acid adsorption can be made strongly dependent on the presence of adsorption-promoting additives and/or repulsion-shielding salts, and removal of these induces elution. Complete water-elutability is demonstrated for baker's yeast RNA bound to 10% Cu(II)- underloaded IDA Chelating Sepharose in a binding buffer of 20,mM HEPES, 240,mM NaCl, pH,7. Water elutability will significantly enhance the utility of IMAC in nucleic acid separations. Copyright © 2006 John Wiley & Sons, Ltd. [source] Metallosupramolecular approach toward functional coordination polymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2005Rainer Dobrawa Abstract An appropriate definition of metallosupramolecular coordination polymer is offered, and the relationship between the polymer length, binding constant, and concentration is clarified. The possibility of influencing the binding constant with chelating ligands is discussed on the basis of examples of different Zn2+ complexes and their respective binding constants. In the main part, coordination polymers constructed by a supramolecular approach from different metal ions and pyridine,ligand systems are highlighted, and their applications as functional materials for artificial membrane and enzyme models, responsive gels, light-harvesting systems, and organic light-emitting diodes are discussed on the basis of individual examples. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4981,4995, 2005 [source] Multinuclear NMR study of some organoplatinum complexes containing multifunctional azines as chelating ligands,MAGNETIC RESONANCE IN CHEMISTRY, Issue 9 2004Dietrich Gudat Abstract 1H-detected indirect NMR techniques were used to determine 15N and 195Pt NMR parameters for a series of organoplatinum(IV) complexes and one platinum(II) complex containing nitrogen-based azobispyridine, bispyridyltetrazine, and bipyrimidine ligands. The inverse technique permitted the detection of small 4J(Pt,H) and 5J(Pt,H) long-range couplings and the acquisition of 15N NMR data in natural isotopic abundance via nJ(N,H) intra- and inter-ligand couplings, but failed in cases where coherence transfer is quenched by rapid relaxation of the metal atom. In one case, analysis of satellite patterns in a set of 1H,15N, 1H,195Pt and 1H,13C correlation spectra allowed a positive sign to be determined for 1J(Pt,15N). Qualitative arguments are presented to explain the observed 15N coordination shifts in complexes with different azine ligands in terms of azine,M dative bond formation and LnM,azine back-donation. Copyright © 2004 John Wiley & Sons, Ltd. [source] Bis(di-2-pyridylamine-,2N2,N2,)(nitrato-,2O,O,)nickel(II) nitrateACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2009Juraj, ernák In the ionic title compound, [Ni(NO3)(C10H9N3)2]NO3, the central NiII atom exhibits cis -NiN4O2 octahedral coordination with three chelating ligands, viz. one nitrate anion and two di-2-pyridylamine (dpya) molecules. A second nitrate group acts as a counter-ion. The complex cations and the nitrate anions are also linked by N,H...O hydrogen bonds. The compound was prepared in two different reproducible ways: direct synthesis from Ni(NO3)2 and dpya yielded systematically twinned crystals (the twinning law is discussed), while single crystals were obtained unexpectedly from the Ni(NO3)2/dpya/maleic acid/NaOH system. [source] Chiral iridium(I) bis(NHC) complexes as catalysts for asymmetric transfer hydrogenationAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 7 2010Claus Diez Abstract The common use of NHC complexes in transition-metal mediated C,C coupling and metathesis reactions in recent decades has established N -heterocyclic carbenes as a new class of ligand for catalysis. The field of asymmetric catalysis with complexes bearing NHC-containing chiral ligands is dominated by mixed carbene/oxazoline or carbene/phosphane chelating ligands. In contrast, applications of complexes with chiral, chelating bis(NHC) ligands are rare. In the present work new chiral iridium(I) bis(NHC) complexes and their application in the asymmetric transfer hydrogenation of ketones are described. A series of chiral bis(azolium) salts have been prepared following a synthetic pathway, starting from L -valinol and the modular buildup allows the structural variation of the ligand precursors. The iridium complexes were formed via a one-pot transmetallation procedure. The prepared complexes were applied as catalysts in the asymmetric transfer hydrogenation of various prochiral ketones, affording the corresponding chiral alcohols in high yields and moderate to good enantioselectivities of up to 68%. The enantioselectivities of the catalysts were strongly affected by the various, terminal N -substituents of the chelating bis(NHC) ligands. The results presented in this work indicate the potential of bis-carbenes as stereodirecting ligands for asymmetric catalysis and are offering a base for further developments. Copyright © 2010 John Wiley & Sons, Ltd. [source] Hemilabile-coordinated copper promoted amination of aryl halides with ammonia in aqueous ethylene glycol under atmosphere pressureAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 4 2009Zhennü Guo Abstract Direct amination of aryl iodides and bromides with ammonia under 1 atm pressure has been effected using in situ -generated hemilabile coordinated copper(I) species from copper(I) halides or copper metal in aqueous ethylene glycol, producing primary aromatic amines in good yields. Ammonia pressure and water were found to accelerate the copper-mediated reaction while strong chelating ligands showed a suppression effect. A rationale for the copper-mediated amination of aryl halides with ammonia is given based on a double-face role of chelating effect. Copyright © 2009 John Wiley & Sons, Ltd. [source] Structure and properties of double- C,N -chelated tri- and diorganotin(IV) halidesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 10 2005Petr Novák Abstract Tri- and di-organotin(IV) compounds containing one or two 2-(dimethylaminomethyl)phenyl- (LCN) groups as chelating ligands were prepared by reactions of lithium compound LCNLi with an appropriate amount of (organo)tin halide. The geometry of tin in 1 ((LCN)2SnPhCl) is on the boundary between octahedral and trigonal bipyramidal. The diorganotin compounds 2,4 ((LCN)2SnX2, where X = Cl, Br, I) have a distorted octahedral geometry in the solid state and show dynamic processes in solution with a lowering of activation energy of the dynamic process going from diiodide to dichloride derivative. Compound 5 (LCNSnPhCl2) has a trigonal bipyramidal structure with non-equivalent chlorine atoms. Copyright © 2005 John Wiley & Sons, Ltd. [source] Microsolvated and Chelated Butylzinc Cations: Formation, Relative Stability, and Unimolecular Gas-Phase ChemistryCHEMISTRY - A EUROPEAN JOURNAL, Issue 46 2009Julia Abstract Solutions of butylzinc iodide in tetrahydrofuran, acetonitrile, and N,N -dimethylformamide were analyzed by electrospray ionization mass spectrometry. In all cases, microsolvated butylzinc cations [ZnBu(solvent)n]+, n=1,3, were detected. The parallel observation of the butylzincate anion [ZnBuI2], suggests that these ions result from disproportionation of neutral butylzinc iodide in solution. In the presence of simple bidentate ligands (1,2-dimethoxyethane, N,N -dimethyl-2-methoxyethylamine, and N,N,N,,N, -tetramethylethylenediamine), chelate complexes of the type [ZnBu(ligand)]+ form quite readily. The relative stabilities of these complexes were probed by competition experiments and analysis of their unimolecular gas-phase reactivity. Fragmentation of mass-selected [ZnBu(ligand)]+ leads to the elimination of butene and formation of [ZnH(ligand)]+. In marked contrast, the microsolvated cations [ZnBu(solvent)n]+ lose the attached solvent molecules upon gas-phase fragmentation to produce bare [ZnBu]+, which subsequently dissociates into [C4H9]+ and Zn. This difference in reactivity resembles the situation in organozinc solution chemistry, in which chelating ligands are needed to activate dialkylzinc compounds for the nucleophilic addition to aldehydes. [source] | |||||||||||||