X-ray Crystallography (x-ray + crystallography)

Distribution by Scientific Domains
Distribution within Chemistry

Kinds of X-ray Crystallography

  • macromolecular x-ray crystallography
  • single-crystal x-ray crystallography

  • Terms modified by X-ray Crystallography

  • x-ray crystallography analysis

  • Selected Abstracts

    1,3-Alternate Calix[4]arene Nitronyl Nitroxide Tetraradical and Diradical: Synthesis, X-Ray Crystallography, Paramagnetic NMR Spectroscopy, EPR Spectroscopy, and Magnetic Studies.

    CHEMINFORM, Issue 49 2007
    Andrzej Rajca
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

    ChemInform Abstract: Structure Studies of Dimeric [Pt2(CN)10]4- Pentacyanoplatinum(III) and Monomeric Pentacyanoplatinum(IV) Complexes by EXAFS, Vibrational Spectroscopy, and X-Ray Crystallography.

    CHEMINFORM, Issue 27 2002
    Farideh Jalilehvand
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    Macrocyclic Cyclo[n]malonates , Synthetic Aspects and Observation of Columnar Arrangements by X-ray Crystallography

    Nikos Chronakis
    Abstract A variety of achiral and chiral macrocyclic oligomalonates were synthesised in a one-step procedure through condensation of malonyl dichloride with ,,,-diols. We have investigated the applicability of this method by varying the length and type of the spacers in the diol. Product distribution analysis revealed that the preferential formation of monomeric, dimeric, or trimeric macrocyclic malonates can be controlled by choosing diols with specific spacers connecting the hydroxy groups. Of special interest are the macrocyclic bismalonates, as they show pronounced crystallisability and arrange into columnar motifs in the solid state. They feature distinctive dihedral angles: all ester moieties adopt anti conformations whereas the planes of the carboxy moieties of each malonate residue arrange in an approximately orthogonal fashion. The latter geometry is enforced by the macrocyclic structures, as revealed by a conformational search in the Cambridge Structural Database. The X-ray diffraction data show that C=OH,C, and C,OH,C hydrogen bonds stabilise the columnar arrangement of the dimeric rings with formation of tubular assemblies. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    Solid-State Structure and Tautomerism of 2-Aminotroponimines Studied by X-ray Crystallography and Multinuclear NMR Spectroscopy

    Rosa M. Claramunt
    Abstract Structural studies in the solid state by X-ray crystallography and by 13C and 15N CPMAS NMR spectroscopy carried out on a series of 2-aminotroponimine derivatives 2,5 has allowed to establish the existence of hydrogen bonding and to determine the most stable tautomer. Almost all the structures reflect the classical double-well potential function for the N,HN hydrogen bonds. Only in the case of the compound N -(pyrrol-1-yl)-2-(pyrrol-1-ylamino)troponimine (5) the crystal structure shows two independent molecules, one with a classical hydrogen bond and another with either a single-well or a low-barrier hydrogen bond. The structure of this compound is discussed with the use of the solid-state NMR spectroscopic data. 2-Aminotropones, as intermediates to the 2-aminotroponimines, show the oxo-tautomer as the stable form. B3LYP/6-31G* calculations are used to rationalise the experimental results. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

    Structure Determination by X-ray Crystallography.

    By Mark Ladd, Rex Palmer.
    First page of article [source]

    Opechowski,Guccione-like symbols labelling magnetic space groups independent of tabulated (0, 0, 0)+ sets

    Hans Grimmer
    For the magnetic space-group types with a black and white lattice two sets of symbols have been proposed: the BNS symbols [Belov et al. (1957). Sov. Phys. Crystallogr.2, 311,322] and the OG symbols [Opechowski & Guccione (1965). Magnetism, edited by G. T. Rado & H. Suhl, Vol. II, Part A, pp. 105,165. New York: Academic Press]. Whereas generators of the group can be read off the BNS symbol, International Tables for X-ray Crystallography (1952) must be consulted to interpret the OG symbols. In the cases where the black and white lattice is centred, it is shown how the OG symbols can be modified so that generators of the group can be deduced directly from the symbol. [source]

    Form factors for core electrons useful for the application of quantum crystallography (QCr) to organic molecules

    Lulu Huang
    Form factors are calculated for the core electrons of the first-row atoms B, C, N, O and F. The form factors are presented in an analytical form, as appears in International Tables for X-ray Crystallography [Ibers & Hamilton (1974), Vol. IV, pp. 103,145. Birmingham: Kynoch Press; present distributor Kluwer Academic Publishers, Dordrecht]. Having such form factors for the core electrons reduces the number of parameters to be determined by the methods of quantum crystallography (QCr). It is shown that the form factors obtained are quite accurate. Thus, when they are used in QCr, they are expected to be consistent with accurate charge densities. [source]

    Structure Determination by X-ray Crystallography.

    By Mark Ladd, Rex Palmer.
    First page of article [source]

    Disparate peptide-dependent thymic selection outcomes in ,2M-deficient mice versus TAP-1-deficient mice: implications for repertoire formation

    Tetsuro Sasada
    Abstract Fetal thymic organ cultures of N15-transgenic RAG-2,/, H-2b mice on normal, ,-2 microglobulin (,2M),/, or transporter associated with antigen processing (TAP-1),/, MHCI-deficient backgrounds were used to examine differentiation of thymocytes bearing a TCR specific for a viral peptide bound to H-2Kb. Strong agonists mediate negative selection in all mice whereas weak agonists are positively selecting in ,2M,/, mice but negatively selecting on TAP-1,/, or normal backgrounds. Very weak agonists and very weak antagonists are generally without effect in ,2M,/, mice yet foster differentiation in TAP-1,/, animals. The 20,40-fold reduction in ,2M,/, thymic H-2Kb surface expression suggests that the avidity of the TCR for peptide,MHCI accounts for these differences, consistent with effects of TCR density and individual thymic-peptide abundance in peptide,MHC complexes. TCR,self-MHC interaction dominates Kb -based selection, subtly modulated by peptides as revealed by X-ray crystallography. [source]

    [FeFe]-Hydrogenase Models: Overpotential Control for Electrocatalytic H2 Production by Tuning of the Ligand ,-Acceptor Ability

    Fengwei Huo
    Abstract In the search for synthetic competitive catalysts that function with hydrogenase-like capability, a series of (Pyrrol-1-yl)phosphane-substituted diiron complexes [(,-pdt)Fe2(CO)5L] [pdt = propanedithiolate, L = Ph2PPyr (2), PPyr3 (4); Pyr = pyrrolyl] and [(,-pdt)Fe2(CO)4L2] [L = Ph2PPyr (3), PPyr3 (5)] were prepared as functional models for the active site of Fe-only hydrogenase. The structures of these complexes were fully characterized by spectroscopy and X-ray crystallography. In the IR spectra the CO bands for complexes 2,5 are shifted to higher energy relative to those of complexes with "traditional" phosphane ligands, such as PPh3, PMe3, and PTA (1,3,5-triaza-7-phosphaadamantane), indicating that (pyrrol-1-yl)phosphanes are poor ,-donors and better ,-acceptors. The electrochemical properties of complexes 2,5 were studied by cyclic voltammetry in CH3CN in the absence and presence of the the weak acid HOAc. The reduction potentials of these complexes show an anodic shift relative to other phosphane-substituted derivatives. All of the complexes can catalyze proton reduction from HOAc to H2 in CH3CN at their respective FeIFe0 level. Complex 4 is the most effective electrocatalyst, which catalytically generates H2 from HOAc at ,1.66 V vs. Fc+/Fc with only ca. 0.2 V overpotential in CH3CN. [source]

    "Tail,Tail Dimerization" of Ferrocene Amino Acid Derivatives

    Daniel Siebler
    Abstract Acid anhydrides of N-protected 1,-aminoferrocene-1-carboxylic acid (Fca) have been prepared and spectroscopically characterized (protection group Boc, Fmoc, Ac; 4a,4c). The structure of the Boc-derivative 4a has been determined by single-crystal X-ray crystallography. An intramolecular N,HO hydrogen bond involving the carbamate units results in a ring structure containing the two ferrocene units, the anhydride moiety, and the hydrogen bond. In the crystal, the individual molecules are connected by intermolecular N,HO hydrogen bonds of the carbamate unit. Experimental and theoretical studies suggest that the ring motif is also a dominant species in solution. Electronic communication across the anhydride moiety is found to be very weak as judged from electrochemical, spectroscopic, and theoretical experiments. [source]

    MS-TOF Study of the Formation of Thiolato-Bridged Rhodium Oligomers

    Jose Boudreau
    Abstract The complex [Cp*Rh(,-SPh)3RhCp*]Cl was used as a starting material to synthesize various oligomeric materials of the general formula [Cp*Rh(,-SPh)x(,-Cl)3,x{Rh(,-SPh)3}nRhCp*] (x = 1 to 3; n = 1 to 4), which are formally formed by insertion of nRh(SPh)3 units into one ,-Rh,SPh bond. The insertion of Ir(SPh)3 was also observed to generate theheterotrimetallic species. All complexes were observed by using HRMS-TOF and [Cp*Rh(,-SPh)3Rh(,-SPh)3RhCp*]Cl, [3+]Cl, was characterized by using X-ray crystallography. [source]

    Assembly of Dinuclear CuII Rigid Blocks by Bridging Azido or Poly(thiocyanato)chromates: Synthesis, Structures and Magnetic Properties of Coordination Polymers and Polynuclear Complexes

    Sergey V. Kolotilov
    Abstract Reaction of a dinuclear cationic copper(II) complex of 4,4,-[2-(3-hydroxyiminobutyl)imino]biphenyl [CuII2(LH)2]2+ with N3, resulted in the formation of a dinuclear azido [CuII2(LH)2(N3)2(H2O)2] complex or a 2D coordination polymer [CuII2(LH)2(N3)2]n. Reaction of the dinuclear complex with [CrIII(NCS)6]3, or [CrIII(NCS)4(NH3)2], produced a 2D polymer {[CuII2(LH)2(CH3CN)2]3[CrIII(NCS)6]2}n or a 1D chain, constructed from tetranuclear units {[CuII2(LH)2][CrIII(NCS)4(NH3)2]2}n. Structures of the compounds were determined by X-ray crystallography and complexes were characterised by the temperature dependency of the magnetic susceptibility and by ESR spectroscopy. Magnetic properties of homometallic compounds were fit with the model of a dimer with the Hamiltonian , = ,J,1,2. For heterometallic complexes ,MT curves were fit as the superposition of magnetism resulting from both [CuII2(LH)2]2+ and the adjacent CrIII -containing anion. J values for the complexes lie in the range from ,12.74(4) to ,17.77(8) cm,1. It was shown that the 4,4,-biphenyl bridge efficiently mediates exchange interactions. [source]

    Synthesis, Crystal Structure, and Catalytic Properties of Novel Dioxidomolybdenum(VI) Complexes with Tridentate Schiff Base Ligands in the Biomimetic and Highly Selective Oxygenation of Alkenes and Sulfides

    Abdolreza Rezaeifard
    Abstract Four novel dioxidomolybdenum(VI) complexes [MoO2(Lx)(CH3OH)] have been synthesized, using 2[(E)-(2-hydroxy-2-phenylethylimino)methyl]phenol derivatives as tridentate ONO donor Schiff base ligands (H2Lx) and MoO2(acac)2. A monoclinic space group was determined by X-ray crystallography from single-crystal data of a sample of these new complexes. The epoxidation of alkenes by using tert -butyl hydroperoxide and oxidation of sulfides to sulfoxides by urea hydrogen peroxide were efficiently enhanced with excellent selectivity under the catalytic influence these new MoVI complexes. The high efficiency and relative stability of the catalysts have been observed by turnover numbers and UV/Vis investigations. The electron-poor and bulky ligands promoted the effectiveness of the catalysts. [source]

    Two New Iron(II) Spin-Crossover Complexes with N4O2 Coordination Sphere and Spin Transition around Room Temperature

    Birgit Weber
    Abstract The reaction of iron(II) acetate with the tetradentate Schiff base like ligand H2L1 {[3,3,]-[4,5-dihydroxy-1,2-phenylenebis(iminomethylidyne)bis(2,4-pentanedion)]} leads to the formation of the complex [FeL1(MeOH)]. Reaction of this complex with pyridine (py) or N,N,-dimethylaminopyridine (dmap) leads to the two N4O2 -coordinated complexes [FeL1(py)2]py (1) and [FeL1(dmap)2]MeOH0.5dmap (2). Both complexes are spin-crossover compounds that were characterised by using magnetic measurements, X-ray crystallography and temperature-dependent 1H NMR spectroscopy. Special attention was given to the role of the two hydroxy groups on the phenyl ring in the formation of a hydrogen-bonding network and the influence of this network on the spin-transition properties. Although only a gradual spin crossover was observed for both complexes, the transition temperature was shifted to higher temperatures relative to that of the complexes with no additional hydroxy groups at the Schiff base like ligand. The hydrogen-bonding network was responsible for this effect.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Copper Complexes with Neutral N4 Tripodal Ligands: Influence of the Number of Nitrogen Donors on Their Structures, Properties, and Reactivity,

    Kiyoshi Fujisawa
    Abstract Copper coordination complexes of the neutral tetradentate nitrogen-containing ligands tris(3,5-dimethylpyrazol-1-ylmethyl)amine (L0N4) and tris(3,5-diisopropylpyrazol-1-ylmethyl)amine (L1N4), namely the copper(II) chlorido complexes [CuII(L0N4)Cl2] (1) and [CuII(L1N4)Cl2] (2), the copper(II) nitrato complexes [CuII(L0N4)(NO3)](NO3) (3) and [CuII(L1N4)(NO3)](NO3) (4), and the copper(II) sulfato complexes [CuII(L0N4)(SO4)] (5) and [CuII(L1N4)(SO4)] (6), and the copper(I) complexes [CuI(L0N4)](PF6) (7) and [CuI(L0N4)(PPh3)](ClO4) (8), have been systematically synthesized in order to investigate the influence of the number of nitrogen donors on their structures, properties, and reactivity. All copper(II) complexes were fully characterized by X-ray crystallography and by IR/far-IR, UV/Vis absorption, and ESR spectroscopy. Although the structure of 7 was not determined by X-ray crystallography, this complex and the structurally characterized copper(I) triphenylphosphane complex 8 were fully characterized by IR/far-IR and NMR spectroscopy. A comparison of the copper(II) complexes with two tris(pyrazol-1-ylmethyl)amine ligands with different bulkiness of the pyrazolyl rings has allowed us to evaluate the second coordination sphere effects of the ligands. Moreover, the structures and physicochemical properties of these complexes are compared with those of related complexes containing the neutral tridentate tris(pyrazolyl)methane ligand and the neutral bidentate bis(pyrazolyl)methane ligand. Finally, the relative stability of the copper(I) complexes is discussed. The influence of the number of nitrogen donors in copper complexes is observed from these systematic results.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Bis(terdentate) Pyrazole/Pyridine Ligands: Synthesis, Crystal Structures and Magnetic Properties of Bridged Binuclear and Tetranuclear Copper(II) Complexes

    Akhilesh Kumar Singh
    Abstract A new binucleating bis(terdentate) ligand, 3,5-[3-bis(2-pyridyl)pyrazole-1-ylmethyl]pyrazole (HL2), was synthesized. Reaction of the deprotonated ligand L2 with hydrated CuII salts gives (,-pyrazolato)(,-hydroxido)-bridged binuclear and tetranuclear complexes [L2Cu2(,-OH)(ClO4)(MeCN)](ClO4) (2), [L2Cu2(dmf)2(,3 -OH)]2(ClO4)44dmf (34dmf) and [L2L,Cu2](ClO4)2 [4; HL, = 3-(2-pyridyl)pyrazole]. In these complexes, both ,-OH and ,3 -OH bridges were observed. This contrasts the situation for a dicopper(II) complex of the related bis(terdentate) ligand 3,5-bis[6(2,2,-dipyridyl)]pyrazole (HL1), {L1Cu2(OMe)(MeOH)[,1 - O -(NO3)]}{[Cu2(NO3)2(,-OMe)2]}0.5MeOH (1MeOH), where the shorter and more rigid ligand side arms enforce a larger CuCu separation and the formation of a MeO,HOMe moiety within the bimetallic pocket. Molecular structures of all complexes were elucidated by X-ray crystallography. Variable-temperature magnetic susceptibility measurements (295,2 K) for powdered samples of complexes 2,4 reveal strong antiferromagnetic coupling between two copper centres. The magnitude of the coupling is discussed in view of the structural features. During the preparation of complex 4, partial ligand hydrolysis was also observed, but this strongly depends on the reaction conditions.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Synthesis, Structure, Conductivity, and Calculated Nonlinear Optical Properties of Two Novel Bis(triphenylphosphane)copper(I) Dithiocarbamates,

    Abhinav Kumar
    Abstract A centrosymmetric binuclear [{Cu(PPh3)2}2(piperzdtc)] (1) [piperzdtc2, = piperazinebis(dithiocarbamate)] and another mononuclear [{Cu(PPh3)2}(BzMedtc)] (2) (BzMedtc, = N -benzyl- N -methyldithiocarbamate) complex have been synthesized and characterized by elemental analyses, IR, 1H, 13C, and 31P NMR spectroscopy and by X-ray crystallography. The nonlinear optical properties of 2 have been investigated by density functional theory and its electronic absorption bands have been assigned by time-dependent density functional theory (TD-DFT). Both complexes are weakly conducting (,rt , 10,8 S,cm,1) because of the absence of MS/SS intermolecular stacking and exhibit semiconductivity with band gaps of 0.94 and 1.24 eV, respectively.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Insertion Reactions of an Aminogermylene and Formation of a Single-Source Precursor for GeTe Thin Films

    Tianniu Chen
    Abstract Insertion reactions between a liquid germylene 1, and either a carbodiimide or dialkyl telluride lead to the formation of the group-14-metal(II) guanidinate complex 2 or the stable group-14-metal terminal alkyl tellurolate compound 3, respectively. The complexes 2 and 3 were structurally elucidated by multinuclear NMR and single-crystal X-ray crystallography. The use of 3 as a single-source precursor (SSP) for the MOCVD of GeTe films was demonstrated. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Solid-State and Solution Structure of Lanthanide(III) Complexes with a Flexible Py-N6 Macrocyclic Ligand

    Cristina Nez
    Abstract Lanthanide complexes of a hexaaza macrocyclic ligand containing a pyridine head unit (L) were synthesized (Ln = La,Lu, except Pm). The solid-state structures of the corresponding La, Ce, Pr, Nd, and Lu complexes were determined by single-crystal X-ray crystallography, and they reveal the presence of three different mononuclear complexes with three different conformations of the macrocycle and coordination environments around the metal ions. In all complexes the lanthanide ion is coordinated in an endomacrocyclic manner to the six nitrogen donor atoms of the ligand. In the La, Ce, and Pr complexes the metal ions show a 12-coordinate mononuclear environment in which 3 nitrate anions coordinate in a bidentate fashion. However, in the Nd analogue the metal ion displays a 10-coordinated environment with the coordination of 2 bidentate nitrate groups, whereas Lu shows a 9-coordinate environment interacting with 2 nitrate ligands, one of them acting as bidentate and the second one coordinating in a monodentate fashion. The 1H and 13C NMR spectra of the complexes recorded in CD3CN suggest that the complexes adopt in solution a similar structure to that observed for the Nd complex in the solid state. The [Ln(L)(NO3)3] and [Ln(L)(NO3)2]+ complexes were characterized by density functional theory (DFT) calculations (B3LYP model). The structures obtained from these calculations for La, Ce, Pr, and Nd are in good agreement with the experimental solid-state structures. The relative stabilities of the [Ln(L)(NO3)2]+ complexes with respect to the [Ln(L)(NO3)3] ones (Ln = La, Nd, Gd, Ho, or Lu) were studied both in vacuo and in acetonitrile solution (PCM model) at the same computational level. Our calculations indicate that in solution the [Ln(L)(NO3)2]+ species is the most stable one along the whole lanthanide series, in agreement with the NMR spectroscopic data.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Pyrazole and Pyrazolyl Complexes of cis -Bis(2,2,-bipyridine)chlororuthenium(II): Synthesis, Structural and Electronic Characterization, and Acid-Base Chemistry

    Hershel Jude
    Abstract Complexes of the type cis -[Ru(bpy)2(Cl)(L)]+ [bpy = 2,2,-bipyridine; with L = pyrazole (1H), 4-methylpyrazole (2H), and 3,5-dimethylpyrazole (3H)] were synthesized and isolated as hexafluorophosphate salts. The molecular structures of these new complexes were fully characterized by 1H NMR spectroscopy and ESI mass spectrometry, and the crystal structure of 3HPF6 was determined by X-ray crystallography. Compound 3HPF6 (C25H24ClF6N6PRu) crystallizes in the monoclinic space group P21/n with a = 12.102(2) , b = 16.826(3) , c = 13.016(2) , , = 92.606(2), V = 2647.6(8) 3, and Z = 4. The crystal structure of 3H reveals the formation of an intramolecular hydrogen bond (2.562 ) between the pyrazole N(2),H site and the chloride ligand. The redox and electronic absorption properties of 1H, 2H, and 3H, as well as their deprotonated counterparts [L = pyrazolate (1), 4-methylpyrazolate (2), and 3,5-dimethylpyrazolate (3)], were investigated by cyclic voltammetry and UV/Vis spectroscopy. For detailed analysis of the electronic nature of this series of pyrazolyl ligands, the results are discussed along with other relevant cis -[Ru(bpy)2(X)(Y)]n+ complexes. From spectrophotometric pH titrations, the basicity associated with the coordinated pyrazole/pyrazolate couple in water was found in all three cases to be unusually high, partly owing to the N,HCl hydrogen bond that stabilizes the protonated, azole state. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Nickel Complexes and Cobalt Coordination Polymers with Organochalcogen (S, Se) Ligands Bearing an N -Methylimidazole Moiety: Syntheses, Structures, and Properties,

    Wei-Guo Jia
    Abstract The organochalcogen ligands (S, Se) derived from 3-methylimidazole-2-thione/selone groups mbit (2a), mbis (2b), ebit (2c), and ebis (2d) [mbit = 1,1,-methylenebis(1,3-dihydro-3-methyl-2H -imidazole-2-thione), mbis = 1,1,-methylenebis(1,3-dihydro-3-methyl-2H -imidazole-2-selone), ebit = 1,1,-(1,2-ethanediyl)bis(1,3-dihydro-3-methyl-1H -imidazole-2-thione), ebis = 1,1,-(1,2-ethanediyl)bis(1,3-dihydro-3-methyl-1H -imidazole-2-selone)] were synthesized and characterized. Mononuclear NiII complexes NiBr2mbit (3a), NiBr2mbis (3b), NiBr2ebit (3c), and NiBr2ebis (3d) were obtained by the reactions of Ni(PPh3)2Br2 with 2a, 2b, 2c, and 2d, respectively. However, when the corresponding ligands 2a, 2b, 2c, and 2d were treated with CoCl2 in thf solution CoII 1D coordination polymers (CoCl2mbit)n (4a), (CoCl2mbis)n (4b), (CoCl2ebit)n (4c), and (CoCl2ebis)n (4d) were obtained. All compounds were fully characterized by IR spectroscopy and elemental analysis. The crystal structures of 2c, 3a, 3b, 3c, 4a, 4b, and 4c were determined by X-ray crystallography. The local geometry around the nickel atom in complexes 3a,c was distorted tetrahedron with coordinated S(Se) and two Br atoms, and the organochalcogen ligands form an eight- or a nine-membered ring with the nickel atom included. The cobalt atom coordination polymers 4a and 4b coexist as left-handed and right-handed helical chains, but 4c formed a zigzag chain with a CH3CN solvent molecule taken up in the channel structure. After activation with methylaluminoxane (MAO), the nickel complexes exhibited high activities for addition polymerization of norbornene (1.42,,108 g,PNBmol,1,Nih,1 for 3a). The effects of the Al/Ni ratio, reaction temperature, and reaction time to norbornene polymerization were also investigated.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Reactivity of Cationic Lanthanide(III) Monoporphyrinates towards Anionic Cyanometallates , Preparation, Crystal Structure, and Luminescence Properties of Cyanido-Bridged Di- and Trinuclear d,f Complexes

    Xunjin Zhu
    Abstract The metathesis reaction between two equivalents of [Ln(tpp)(H2O)3]Cl (Ln = Yb, Er; tpp2, = tetraphenylporphyrinate dianion) and one equivalent of cyanometallate in dmf at room temperature under nitrogen for 24 hours gave the cyanido-bridged d,f trinuclear complexes [{Ln(tpp)(dmf)n}2{(,-NC)2M(CN)2}] (Ln = Yb, n = 2, M = Ni, 1; Ln = Er, n = 3, M = Ni, 2; Ln = Yb, n = 2, M = Pt, 3; Ln = Er, n = 3, M = Pt, 4), a trinuclear complex [{Er(tpp)(dmf)2}{(,-NC)2Fe(CN)4}{Er(Htpp)(dmf)2}] (5), and a dinuclear complex [{Er(tpp)(dmf)(H2O)}(,-NC)Ag(CN)] (6) when the cyanometallate used was the dianion [M(CN)4]2, (M = Ni, Pt), the trianion [Fe(CN)6]3,, and monoanion [Ag(CN)2],, respectively. The solid-state structures of these complexes were ascertained by X-ray crystallography. Photoluminescence studies of complexes 1,4 showed that these complexes displayed photophysical properties characteristic of normal metal,porphyrinato complexes. Their absorption bands and emission peaks in the visible region are typical of the intraligand ,,,* transitions of the porphyrinato ligand. Furthermore, these complexes also exhibited emission characteristic of the lanthanide(III) ion in the near-infrared (NIR) region, which was quenched by the cyanometallates. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Reactions of [Hg(Tab)2](PF6)2 [Tab = 4-(trimethylammonio)benzenethiolate] with NaX (X = Cl, NO2, NO3): Isolation and Structural Characterization of a Series of Mono- and Binuclear Hg/Tab/X Compounds

    Xiao-Yan Tang
    Abstract The complex [Hg(Tab)2](PF6)2 [Tab = 4-(trimethylammonio)benzenethiolate] (1) reacts with one or two equivalents of NaCl to afford the mononuclear complex [Hg(Tab)2Cl](PF6) (2) and the dinuclear complex [{Hg(,-Tab)(Tab)Cl}2]Cl2H2O (3H2O), respectively. Similar reactions of 1 with NaCl and NaX (molar ratio = 1:1) produce the dinuclear species [{Hg(,-Tab)(Tab)Cl}2]X2 [X = NO2 (4), NO3 (5)], while those with NaNO2 or NaNO3 give rise to [{Hg(,-Tab)(Tab)X}2]X2 [X = NO2 (6), NO3 (7)]. Complexes 2,7 have been characterised by elemental analysis, IR, UV/Vis, and 1H NMR spectroscopy, and X-ray crystallography. The Hg atom of the [Hg(Tab)2Cl]+ cation in 2 adopts a T-shaped coordination geometry. Two [Hg(Tab)2Cl]+ cations in 3H2O, 4, and 5 are linked by a pair of weak Hg,S bonds to form a dimeric [Hg(,-Tab)(Tab)Cl]22+ dication, and the centrosymmetric [Hg(,-Tab)(Tab)X]22+ dication in 6 and 7 consists of two [Hg(Tab)2X]+ cations linked by a couple of weak Hg,S bonds. The hydrogen-bonding interactions in 2,7 lead to the formation of interesting 2D (5, 7) or 3D (2,4, 6) hydrogen-bonded networks.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Structure,Catalytic Activity Relationship in Bridging Silacycloalkyl Ring Conformations of Constrained Geometry Titanium Complexes

    Eugene Kang
    Abstract A series of cyclic silylene-bridged (amidocyclopentadienyl)dichlorotitanium(IV) complexes [TiCl2{,5 -1-(CySitBuN- ,N)-2,3,4,5-R4 -C5}] was prepared, where CySi = silacyclobutyl (a), silacyclopentenyl (b), silacyclopentyl (c), and silacyclohexyl (d); R = H (4), Me (5). The starting silane, dichlorosilacycloalkane CySiCl2 (1), was treated with NaCp (LiCp*), followed by LiNHtBu to yield the cyclic silylene-bridged ligands (R4C5)CySi(NHtBu) [R = H (2); Me (3)]. Subsequent deprotonation with n -butyllithium, followed by transmetalation with TiCl4 yielded the desired constrained geometry complexes (CGCs) (CpCySiNtBu)TiCl2 (4) and (Cp*CySiNtBu)TiCl2 (5). The structures of the resulting cyclopentadienyl- (4b and 4c) and tetramethylcyclopentadienyl(silacycloalkyl)amidotitanium(IV) dichloride (5a, 5c, and 5d) species were studied by using X-ray crystallography to obtain geometrical information on cyclic silylene-modified CGCs. The ethylene polymerization by the cyclic silylene-bridged CGCs 4 and 5 was examined to verify the structure,catalytic activity relationship derived from variation of the size of a cyclic silylene ring. Indeed, the size of the cyclic silylene ring at the 1,1,-position of 4 and 5 affected the catalytic activities through the ethylene polymerization. Systematic increase in the catalytic activities was observed as the cyclic silylene-bridging unit was expanded from a four- to six-membered ring. In the present study, we found that CGCs of TiIV with a six-membered silylene-bridged ligand (5d) produced active catalytic species for the formation of polyethylene with Mw = 42.7,,10,4 g,mol,1 and Mw/Mn = 2.1 with excellent catalytic activities (20.9 kg,polymer per mmol of Ti). When titanium(IV) dimethyl complex (6d) was applied in continuous polymerization process, impressive high catalytic activity on copolymerization with 1-octene was observed. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Electron-Sponge Behavior, Reactivity and Electronic Structures of Cobalt-Centered Cubic Co9Te6(CO)8 Clusters

    Mustapha Bencharif
    Abstract Extended investigations of the reaction sequence [Cp,2Nb(Te2)H]/CH3Li/[Co2(CO)8] (Cp, = tBuC5H4) led to the identification of Lin[3] {3 = [Co9Te6(CO)8]; n = 1, 2} salts through their transformation with [PPN]Cl into [PPN]n[3] (PPN = Ph3PNPPh3). These compounds form in the solid state columnar ([PPN][3]) or undulated 2D ([PPN]2[3]) supramolecular networks. Electrochemical studies of [Cp*2Nb(CO)2][3] (Cp* = C5Me5) or [Na(THF)6][3] revealed the presence of the redox couples [3],/[3]2,/[3]3,/[3]4,/[3]5, regardless of the nature of the cation, whereas in the anodic part oxidative degradation of the cluster takes place. This behavior is in agreement with the observation that [3], containing salts form with PPh3AuCl or dppe decomposition products like [(PPh3)2Au][CoCl3PPh3] or [Co(CO)2dppe]2(,-Te). A neutral cluster comprising the Co@Co8(,4 -Te)6 core formed in the reaction of [Cp*2Nb(CO)2][Co11Te7(CO)10] with PPh3AuCl, which gave [Co9Te6(CO)4(PPh3)4] (4) after oxidative cluster degradation and CO substitution. 4 was characterized by X-ray crystallography. DFT calculations carried out on all members of the [3]n (n = +1 to ,5) family and on related species indicate that there is no significant Jahn,Teller distortion (and therefore no connectivity change) for any of the considered electron counts. Magnetic investigations on [PPN][3] show that the ground state of [3], is a spin triplet with spins interacting antiferromagnetically in a 1D space.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Influence of the Diketonato Ligand on the Cytotoxicities of [Ru(,6 - p -cymene)(R2acac)(PTA)]+ Complexes (PTA = 1,3,5-triaza-7-phosphaadamantane)

    Carsten A. Vock
    Abstract A series of compounds of general formula [Ru(,6 - p -cymene)(R2acac)(PTA)][X] (R2acac = Me2acac, tBu2acac, Ph2acac, Me2acac-Cl; PTA = 1,3,5-triaza-7-phosphaadamantane; X = BPh4, BF4), and the precursor to the Me2acac-Cl derivative [Ru(,6 - p -cymene)(Me2acac-Cl)Cl], have been prepared and characterised spectroscopically. Five of the compounds have also been characterised in the solid state by X-ray crystallography. The tetrafluoroborate salts are water-soluble, quite resistant to hydrolysis, and have been evaluated for cytotoxicity against A549 lung carcinoma and A2780 human ovarian cancer cells. The compounds are cytotoxic towards the latter cell line, and relative activities are discussed in terms of hydrolysis (less important) and lipophilicity, which appears to exert the dominating influence. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Selenium Heterocycles: Reactions of SeX4 (X = Cl, Br) with the Enamine Form of ,-Diketiminato Ligands

    Audra F. Gushwa
    Abstract Treatment of SeX4 (X = Cl, Br) with either MesnacnacLi(nacnac = [{N(Ar)C(Me)}2CH],, Ar = Mes = C6H2Me3 -2,4,6) or DmpnacnacLi (Ar = Dmp = C6H3Me2 -2,6) affords four new SeII six-membered heterocycles, [MesnacnacHCl2SeCl] (2), [MesnacnacH2Se]+Br, (3), [DmpnacnacH2Cl3Se]+Cl, (4), and [MesnacnacH2(O)Br2Se] (5). All have been characterized in the solid state by X-ray crystallography. Each of the four complexes is proposed to have formed from the initial reaction of SeX4 with the C,C double bond that results from the enamine form of the ligand, giving rise to an Se,C single bond. Subsequent nucleophilic attack by either the more distant nitrogen atom or the remaining C,C double bond of the enamine form results in the Se heterocycle. In complexes 2, 4, and 5 varying degrees of halogenation of the newly formed heterocycles was observed.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    New Coordination Modes of L -Ascorbic Acid and Dehydro- L -ascorbic Acid as Dianionic Chelating Ligand for Platinum

    Paola 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]

    The N -Acylated Derivatives of Parent Complex [{(,-SCH2)2NH}Fe2(CO)6] as Active Site Models of Fe-Only Hydrogenases: Synthesis, Characterization, and Related Properties

    Li-Cheng Song
    Abstract A series of N -acylated diiron azadithiolate complexes as H-cluster models was synthesized and structurally characterized. Treatment of parent complex [{(,-SCH2)2NH}Fe2(CO)6] (A) with 2-chloroacetic acid in the presence of dicyclohexylcarbodiimide or with 2-chloroacetyl chloride in the presence of Et3N gave N -chloroacetyl complex [{(,-SCH2)2NC(O)CH2Cl}Fe2(CO)6] (1). Further treatment of 1 with MeC(O)SK afforded N -acetylthioacetyl complex [{(,-SCH2)2NC(O)CH2SC(O)Me}Fe2(CO)6] (2). N -Ethoxylcarbonylacetyl complex [{(,-SCH2)2NC(O)CH2CO2Et}Fe2(CO)6] (3) and N-heterocyclic complexes [{(,-SCH2)2NC(O)C4H3Y-2}Fe2(CO)6] (4, Y = O; 5, Y = S) were produced by reactions of A with EtO2CCH2C(O)Cl, 2-furancarbonyl chloride, and 2-thiophenecarbonyl chloride in the presence of pyridine or Et3N. Similarly, N -malonyl complex [{Fe2(CO)6(,-SCH2)2NC(O)}2CH2] (6) and N -carbonylbenzaldehyde complex [{(,-SCH2)2NC(O)C6H4CHO- p}Fe2(CO)6] (7) could be obtained by reaction of A with malonyl dichloride in the presence of pyridine and with p -CHOC6H4C(O)Cl in the presence of Et3N. More interestingly, further reaction of 7 with PhCHO and pyrrole in a 1:3:4 molar ratio in the presence of BF3OEt2 followed by p -chloranil yielded the first light-driven type of model complex containing an N -carbonylphenylporphyrin moiety [{(,-SCH2)2NC(O)(TPP)}Fe2(CO)6] (8, TPP = tetraphenylporphyrin group). Whereas the molecular structures of 2, 5, and 7 were established by X-ray crystallography, the electrochemical properties of 2,5 as well as the proton reduction to hydrogen gas catalyzed by 2 and 3 were studied by CV techniques.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]