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ABSTRACT: The new compound LaSr(3)F(5)(CN(2))(2) was prepared and structurally characterized as a prototype structure for the remarkably distorted mixed-valent compound Eu(4)F(5)(CN(2))(2), which contains four distinct europium ions in the structure: one Eu(3+) and three Eu(2+). Instead of repeating the given distorted structural pattern, LaSr(3)F(5)(CN(2))(2) forms a structure which can be considered as an ideal high-symmetry structure for Eu(4)F(5)(CN(2))(2), due to the occupation of La(3+) and Sr(2+) ions on one and the same crystallographic position. The crystal symmetry of this structure is an interesting issue to compare with what has been previously proposed.
Inorganic Chemistry 11/2012; · 4.60 Impact Factor
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ABSTRACT: Coordination chemistry of gold catalysts bearing eight different ligands [L=PPh(3) , JohnPhos (L2), Xphos (L3), DTBP, IMes, IPr, dppf, S-tolBINAP (L8)] has been studied by NMR spectroscopy in solution at room temperature. Cationic or neutral mononuclear complexes LAuX (L=L2, L3, IMes, IPr; X=charged or neutral ligand) underwent simple ligand exchange without giving any higher coordinate complexes. For L2AuX the following ligand strength series was determined: MeOH≪hex-3-yne <MeCN≈OTf(-) ≪Me(2) S<2,6-lutidine<4-picoline<CF(3) CO(2) (-) ≈DMAP<TMTU<PPh(3) <OH(-) ≈Cl(-) . Some heteroligand complexes DTBPAuX exist in solution in equilibrium with the corresponding symmetrical species. Binuclear complexes dppf(AuOTf)(2) and S-tolBINAP(AuOTf)(2) showed different behavior in exchange reactions with ligands depending on the ligand strength. Thus, PPh(3) causes abstraction of one gold atom to give mononuclear complexes LLAuPPh(3) (+) and (Ph(3) P)(n) Au(+) , but other N and S ligands give ordinary dicationic species LL(AuNu)(2) (2+) . In reactions with different bases, LAu(+) provided new oxonium ions whose chemistry was also studied: (DTBPAu)(3) O(+) , (L2Au)(2) OH(+) , (L2Au)(3) O(+) , (L3Au)(2) OH(+) , and (IMesAu)(2) OH(+) . Ultimately, formation of gold hydroxide LAuOH (L=L2, L3, IMes) was studied. Ligand- or base-assisted interconversions between (L2Au)(2) OH(+) , (L2Au)(3) O(+) , and L2AuOH are described. Reactions of dppf(AuOTf)(2) and S-tolBINAP(AuOTf)(2) with bases provided more interesting oxonium ions, whose molecular composition was found to be [dppf(Au)(2) ](3) O(2) (2+) , L8(Au)(2) OH(+) , and [L8(Au)(2) ](3) O(2) (2+) , but their exact structure was not established. Several reactions between different oxonium species were conducted to observe mixed heteroligand oxonium species. Reaction of L2AuNCMe(+) with S(2-) was studied; several new complexes with sulfide are described. For many reversible reactions the corresponding equilibrium constants were determined.
Chemistry 09/2012; · 5.93 Impact Factor
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ABSTRACT: Tetracyanamidoaluminates of the type LiM(2)[Al(CN(2))(4)] with M = Eu and Sr were prepared by solid-state metathesis reactions departing from EuF(2) (or SrF(2)), AlF(3), and Li(2)(CN(2)) in a 2 : 1 : 4 molar ratio. The ignition temperature of the exothermic formation of LiSr(2)[Al(CN(2))(4)] was obtained near 420 °C. An X-ray single-crystal structure refinement performed for LiEu(2)[Al(CN(2))(4)] revealed the presence of the novel homoleptic [Al(CN(2))(4)](5-) ion in the structure. The X-ray powder diffraction pattern of LiSr(2)[Al(CN(2))(4)] was indexed isotypically.
Dalton Transactions 08/2011; 40(38):9921-4. · 3.84 Impact Factor
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ABSTRACT: The new europium fluoride carbodiimide Eu(4)F(5)(CN(2))(2) was synthesized by solid state reaction from mixtures of EuF(3) and Li(2)(CN(2)) at 700 °C. The crystal structure as refined by single crystal X-ray diffraction (P ̅42(1)c, no. 114, a = 16.053(1) Å, c = 6.5150(6) Å, Z = 8) reveals three crystallographically distinct [N═C═N](2-) ions in the structure of mixed-valent Eu(4)F(5)(CN(2))(2). The presence of one Eu(3+) and three Eu(2+) per formula unit Eu(4)F(5)(CN(2))(2) is confirmed by magnetic measurements and (151)Eu-Mössbauer spectroscopy. The arrangement of Eu ions and gravity centers of [NCN](2-) ions in the structure of Eu(4)F(5)(CN(2))(2) follow the motif formed by atoms in the CuAl(2)-type structure. A possible high-symmetry structure of Eu(4)F(5)(CN(2))(2) is discussed on the basis of a group-subgroup scheme.
Inorganic Chemistry 07/2011; 50(13):6010-8. · 4.60 Impact Factor
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Berichte der deutschen chemischen Gesellschaft 05/2011; 2011(26):4063 - 4068. · 2.94 Impact Factor
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ABSTRACT: An effective total synthesis of (-)-9-deoxy-englerin (4), an analogue of the natural guaiane sesquiterpene englerin A (1), has been achieved. The synthesis features a transannular epoxide opening to construct the 5,7-fused ring system followed by transannular ether formation with mercury(II) trifluoroacetate.
Organic Letters 03/2011; 13(8):2090-3. · 5.86 Impact Factor
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ABSTRACT: A cyclic carbonyl ylide with a trans-annulated cyclopentane ring was generated by a Rh(2)(OAc)(4)-catalyzed reaction from a diazoketone precursor and trapped with allyl propiolate. The 1,3-dipolar cycloaddition led to the stereoselective formation of an oxygen-bridged polycycle. Via Curtius degradation, the cycloadduct was transformed to the ring skeleton typical of the sesquiterpene family of guaianolides.
Organic Letters 08/2010; 12(15):3418-21. · 5.86 Impact Factor
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ABSTRACT: Reactions between W(6)Cl(12) and carbon halides can initiate a cascade of reactions and reaction products, yielding W(6)Cl(18), W(6)CCl(18), and W(6)CCl(15) with increasing temperature, before decomposition into tungsten carbide is obtained. The new compound W(6)CCl(15) and the new heteroleptic compound W(30)C(2)(Cl,Br)(68) obtained from these reactions were structurally characterized. The structure of W(30)C(2)X(68) combines a carambolage of two distinct octahedral and one centered trigonal prismatic cluster in one structure as refined by X-ray single-crystal diffraction (P1, Z = 1; a = 12.003(2) A, b = 14.862(3) A, c = 15.792(3) A, alpha = 88.75(2) degrees, beta = 68.85(2) degrees, gamma = 71.19(2) degrees). The unit cell content W(30)C(2)X(68) accommodates five hexanuclear tungsten clusters, similar by a total of three octahedral [W(6)X(8)] type clusters and two carbon-centered trigonal prismatic [W(6)CX(12)] type clusters, sharing terminal halogen atoms to form a network structure. The trigonal prismatic cluster compound W(6)CCl(15) (P2(1)/c, Z = 4; a = 9.8830(4) A, b = 11.8945(4) A, c = 17.8670(7) A, beta = 107.883(2) degrees) is related to the already known compound W(6)CCl(16). According to X-ray powder structure refinement, the structure is showing a special connectivity pattern with short intercluster W-W contacts between trigonal prismatic cluster units.
Inorganic Chemistry 07/2010; 49(13):5986-91. · 4.60 Impact Factor
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ABSTRACT: Solid state metathesis reactions have been established as a successful tool in syntheses of rare earth carbodiimide compounds. Current results evidence the new compounds LiRE(CN2)2 with RE = La, Ce and the carbodiimide nitride Ce3(CN2)3N. LiRE(CN2)2 compounds were synthesized by solid state metathesis reactions between REF3 and Li2(CN2) in 1:2 molar ratio. Ce3(CN2)3N was obtained by thermal conversion of LiCe(CN2)2., Crystal structures of LiLa(CN2)2 and Ce3(CN2)3N were determined from X-ray single crystal data (LiLa(CN2)2: P21/m, a = 542.4(2) pm, b = 379.16(7) pm, c = 1013.0(3) pm, β = 101.35(3) °; Ce3(CN2)3N: P212121, a = 672.97(9) pm, b = 1309.8(2) pm, c = 1697.7(3) pm) and LiCe(CN2)2 was assigned from indexed X-ray powder diffraction data (LiCe(CN2)2: a = 541.9(1) pm, b = 374.50(8) pm, c = 1008.8(2) pm, β = 101.21(1) °)., The crystal structure of LiLa(CN2)2 represents a layer-like arrangement of ions as typical for this type of compounds. The crystal structure of Ce3(CN2)3N reveals chains of [NCe4] tetrahedra running parallel to each other, and trigonal prismatic to trigonal antiprismatic arrangements of six distinctly interconnected [Ce3–NCN–Ce3] units. Both structures contain (CN2)2– ions deviating from their ideal D∞h symmetry, with C–N distances ranging between 121 and 126 pm and N–C–N angles near 180°.
Zeitschrift für anorganische Chemie 09/2009; 635(12):1947 - 1952.
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ABSTRACT: Cluster compounds of the general formula A(2)[W(6)Cl(18)] containing singly charged A cations (A = K, Rb, Ag, Tl, NH(4), N(C(2)H(5))(4), N(n-C(3)N(7))(4), N(n-C(4)H(9))(4)) and [W(6)Cl(18)](2-) anions have been synthesized. Compounds were obtained by W(6)Cl(18) reduction using methanol and the corresponding metal or (alkyl-)ammonium salts. The use of CoCp(2) as reducing agent in inert solvents such as tetrahydrofurane also leads to the ionic compound (Co(C(5)H(5))(2))(2)[W(6)Cl(18)]. All compounds described here evidence the existence of octahedral clusters of the M(6)X(12) type with 20 cluster electrons occupying metal centered states, thus exceeding the conventional number of 16 electrons for this cluster type. Electrospray ionization (ESI) mass spectra were recorded for the neutral compound W(6)Cl(18) and for the ionic salts K(2)[W(6)Cl(18)], Cs(2)[W(6)Cl(18)], and (Co(C(5)H(5))(2))(2)[W(6)Cl(18)], showing that the cluster W(6)Cl(18) unit in these compounds is preserved in solution. The base peak in the ESI spectra for all compounds corresponds to the [W(6)Cl(18)](2-) anion, so that neutral W(6)Cl(18) is prone to undergo a two electron reduction process. This result is confirmed by cyclic voltammetry experiments, which makes of W(6)Cl(18) a very clean mild oxidizing agent. The preparation of the complete series of ionic A(2)[W(6)Cl(18)] (A = K, Cs, CoCp(2)) clusters allows to systematically investigate their structural trends as function of the distinctive cations, which is the main focus of the present work.
Inorganic Chemistry 05/2009; 48(8):3825-31. · 4.60 Impact Factor
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ABSTRACT: Two new aminophenoxazinone compounds with antitumor activity, elloxazinone A and B, were isolated from the culture filtrate of Streptomyces griseus Acta 2871. Their chemical structures were determined by mass spectrometry, NMR spectroscopy and X-ray analysis. Elloxazinones A and B showed a moderate inhibition of the proliferation of human cells from gastric adenocarcinoma in vitro but a strong inhibition of hepatocellular carcinoma cells whereas elloxazinone B strongly inhibited the proliferation of human breast carcinoma cells.
The Journal of Antibiotics 05/2007; 60(4):277-84. · 1.65 Impact Factor
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ABSTRACT: Three new fluostatin antibiotics have been isolated from the culture filtrate of Streptomyces strain Acta 1383. The chemical structures of these compounds were determined by mass spectrometry and NMR spectroscopy. The relative configuration has been determined by X-ray crystal structure analysis and the absolute configuration was deduced from NMR data with the help of Helmchen esters. These compounds represent the first reported epoxide fluostatins (1, 2) and underline previously found analogies to the group of kinamycin antibiotics.
The Journal of Antibiotics 03/2006; 59(2):105-9. · 1.65 Impact Factor
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ABSTRACT: A comprehensive 31P solid-state NMR study of Ru(eta1-Ph2PCH2CH2OCH3)2(eta2-en)Cl2 (en = ethylenediamine) (1), by 1D (contact time variation, inversion-recovery, SPARTAN) and 2D techniques (homonuclear J-resolved, SECSY) indicated that the crystal structure of 1 should be complex. The single-crystal x-ray structure determination confirmed the presence of eight independent molecules in the asymmetric unit, with 31P isotropic chemical shifts in the range 27.3-40.1 ppm, while the spans of the phosphorus chemical shift tensors are of the order of 170 ppm. Based on unique structural features and NMR data, one molecule has been tentatively assigned.
Magnetic Resonance in Chemistry 10/2004; 42(9):807-13. · 1.44 Impact Factor
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Angewandte Chemie International Edition 06/2004; 43(19):2574-6. · 13.45 Impact Factor
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ABSTRACT: Thiocyanate cadmium and methylviologen hybrid host-guest compounds give two novel multiple sandwich architectures with regular or irregular grids of the anionic layer in the structures as effected by the molar ratios of starting ingredients, and show evidence of charge-transfer to the organic dications.
Chemical Communications 04/2004; · 6.17 Impact Factor
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ABSTRACT: Solid state metathesis reactions have been studied in fused silica tubes, by differential thermal analysis, and by X-ray powder diffraction. A selection of reactions between metal (La, Nb, and Ni) chlorides and lithium nitride or lithium acetylide were investigated to get more insight into reaction pathways and intermediate reaction stages that may be adopted on course of the formation of metal nitrides or carbides. Intermediate compounds are considered to be important because they can control the reactivity of a system. Such compounds were traced by changing the molar ratios of reaction partners away from the salt-balanced binary metal nitride or carbide target compositions.New preparative perspectives are discovered when metal chlorides were reacted with lithium nitridoborate or lithium cyanamide. Due to their reductive nature towards several d-block metal chlorides, (BN2)3- and (CN2)2- react to form metals or metal nitrides plus X-ray amorphous BN, and probably C3N4. With lanthanum chloride they can react to form nitridoborates and nitridocarbonates. The metathesis reaction between lithium cyanamide and cyanuric chloride (C3N3Cl3) instead of metal chloride was studied for the synthesis of C3N4.Festkörper-Metathesereaktionen in verschiedenen AnwendungenFestkörper-Metathesereaktionen wurden in zugeschmolzenen Quarzglasampullen, durch Differenz-Thermoanalyse und über Pulver-Röntgenbeugung untersucht. Eine Auswahl von Reaktionen zwischen Metallchloriden (La, Nb und Ni) und Lithiumnitrid oder Lithiumcarbid wurde untersucht, um nähere Aufschlüsse über Reaktionswege und Zwischenstufen bei der Bildung von Metallnitriden und -carbiden zu gewinnen. Intermediär auftretende Verbindungen erscheinen dabei von Bedeutung, weil sie die Reaktivität eines Systems maßgeblich beeinflussen können. Versuche zur Aufspürung solcher Verbindungen wurden unternommen, indem die molaren Verhältnisse der Reaktionspartner von den salzbalancierten Zusammensetzungen, die zur Bildung reiner Metallnitride oder Metallcarbide führen, variiert wurden.Neue präparative Perspektiven eröffnen sich durch Reaktionen von Metallchloriden mit Lithiumnitridoborat oder Lithiumcyanamid. Durch das reduktive Verhalten von (BN2)3- und (CN2)2- gegenüber 3d-Metallchloriden entstanden bei den Reaktionen elementare Metalle oder Metallnitride plus röntgenamorphes BN und vermutlich C3N4. Mit Lanthanchlorid entstehen Nitridoborate und Nitridocarbonate. Im Zusammenhang mit der Bildung von C3N4 wurden Metathesereaktionen untersucht, in denen Cyanurchlorid (C3N3Cl3) anstatt eines Metallchlorids zur Reaktion mit Lithiumcyanamid eingesetzt wurde.
Zeitschrift für anorganische Chemie 09/2003; 629(10):1863 - 1870.
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ABSTRACT: Solid state metathesis reactions between RECl(3) (RE = La, Ce) and Li(2)CN(2) at 800 degrees C have led to the discovery of the rare earth chloride carbodiimide nitrides La(2)Cl(CN(2))N (1) and Ce(2)Cl(CN(2))N (2), respectively. Single crystal X-ray diffraction analyses revealed that 1 and 2 crystallize isotypic in an orthorhombic system (Cmmm, Z = 4, a = 13.3914(8) A, b = 9.6345(7) A, c = 3.9568(2) A for 1 and a = 13.340(1) A, b = 9.5267(8) A, c = 3.9402(5) A for 2). The crystal structures of 1 and 2 contain linear chains of edge-sharing octahedra built from rare earth metal atoms. Similar to [M(6)X(8)] type clusters, the [RE(6)] octahedra are capped by eight nitrogen atoms above their faces, of which four are from N(3-) ions and the other four are from (CN(2))(2-) ions. The chains are interconnected by bridging (CN(2))(2-) to form a three-dimensional network with Cl(-) ions in linear channels. Compounds 1 and 2 are surprisingly stable toward air and water. They have been characterized by thermal analysis, infrared spectroscopy, and magnetic susceptibility studies.
Inorganic Chemistry 07/2003; 42(11):3406-11. · 4.60 Impact Factor
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ABSTRACT: The macrocyclic complexes [(η5-C5H4C2-4-py)2Fe]2Ni2(NO3)4 (2), [(η5-C5H4C2-3-py)2Fe]2Ag2(ClO4)2 (4), and [(η5-C5H4C2-3-py)2Fe]2Pd2Cl4 (5) were obtained by reaction of [Ni(H2O)6](NO3)2, AgClO4, and PdCl2(COD) with the ligands (η5-C5H4C2-4-py)2Fe (1) and (η5-C5H4C2-3-py)2Fe (3), respectively, under high dilution conditions (Scheme 1). The molecular motifs of 2, 4, and 5 were studied by single-crystal X-ray structural investigations. Elemental analyses and 1H NMR and IR spectra were also used to confirm the structures. Compound 2 represents an unsymmetric paddlewheel, in which the centers of the four Cp rings define a nearly ideal rectangle with dimensions of 20.2 × 3.3 Å. In principle, macrocycles 4 and 5 can also be described as rectangles, however, due to the 3-positioned nitrogen donors with deformed edges (17.4 × 3.3 Å for 4). In contrast to the offset packing of the molecules in 2, the macrocycles in the crystal of 4 are aligned, with trapped acetonitrile molecules in between. The intra- and intermolecular Ag−Ag distances are 3.50 and 3.79 Å, respectively. Cyclovoltammetric studies reveal chemically reversible ferrocene-based redox reactions of 1−4. Although no electronic communication was observed between the two identical ferrocene units, a weak through-bond electronic interaction between ferrocene and nickel, or silver, was established. In 2 a weak antiferromagnetic interaction between the nickel atoms was also found. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Berichte der deutschen chemischen Gesellschaft 02/2003; 2003(4):705 - 712. · 2.94 Impact Factor
