Browsing by Author "Daran, JC"

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    Reduction of [CP2*Mo2O5] by thioglycolic acid in an aqueous medium
    Demirhan, F; Taban, G; Baya, M; Dinoi, C; Daran, JC; Poli, R
    Compound [CP*2Mo2O5] reacts with thioglycolic acid, HSCH2COOH, in an acidic (CF3COOH) mixed water-methanol solvent, to yield compound [{Cp*Mo(mu-SCH2CO2)}(2)(mu-S)]. During this reaction, the thioglycolic acid acts as a reducing agent, as a ligand, and provides a sulfide ion for the Mo-S-Mo bridge. The molecular structure of the product can be described as containing two four-legged piano stools that share three legs. The Mo-Mo distance of 2.792(7) angstrom indicates metal-metal bonding, in agreement with the compound diamagnetism. (c) 2005 Elsevier B.V. All rights reserved.
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    Reduction of [Cp*2Mo2O5] in aqueous medium: Structure and properties of a triangular mixed oxo-hydroxo-bridged product, [Cp*3Mo3(μ-O)2(μ-OH)4](X)2 (X =CF3CO2 or CF3SO3)
    Demirhan, F; Çagatay, B; Demir, D; Baya, M; Daran, JC; Poli, R
    The reduction of [CP*2MO2O5] with Zn in a MeOH/H2O solotion acidified with either CF3COOH or CF3SO3H leads to the formation of the [CP*3MO3(mu-O)(2)(mu-OH)(4)](2+) ion as its trifluoroacetate or trifluoromethanesulfonate salt. The structure of the compound was confirmed by X-ray analyses. The anions establish hydrogen-bonding interactions with all four bridging OH groups. Density functional calculations afford bonding parameters in close agreement with the observed structure and indicate that the cluster is best described as a valence-delocalized Mo-3(13+) species. The five metal electrons are distributed among an a-type (z(2)) orbital, which accounts for most of the metal-metal attraction, and two essentially metal-metal nonbonding e-type (xy) orbitals with a slight Mo(mu-O) pi*-type contribution. Because of the C-2 symmetry, the latter orbitals are not degenerate. The calculations show that the unpaired electron is located in a molecular orbital with equal contribution from two Mo atoms, in agreement with the experimental observation of coupling of the unpaired electron to two Mo atoms in the isotropic EPR spectrum. (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Gerniany, 2006.
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    Reduction of [CP*2Mo2O5] by mercaptopropionic acid in an aqueous medium. Isolation and characterization of a dinuclear oxo- and 3-sulfido-proprionato(2-)-bridged molybdenum(IV) compound
    Dinoi, C; Prikhodchenko, P; Demirhan, F; Gun, J; Lev, O; Daran, JC; Poli, R
    Reaction of Cp-2*Mo2O5 with HSCH2CH2COOH in acidic (by CF3COOH) 50:50 MeOH-H2O solvent at room temperature yields compound Cp-2*Mo-2(mu-O)(mu-SCH2CH2CO2)(2), a dinuclear diamagnetic Mo-IV compound with a two-leg-sharing bis(four-legged piano stool) structure and a Mo-Mo distance of 2.6833(6) angstrom. A reaction monitoring by ESI MS shows the formation of an intermediate 18 mass units heavier, interpreted as a dihydroxo analogue. Electrochemistry shows a reversible, pH independent oxidation process and an irreversible, pH-dependent reduction process. Contrary to a recently published analogous reaction with the closely related HSCH2COOH substrate, this process does not lead to C-S bond cleavage. (c) 2007 Elsevier B.V. All rights reserved.
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    Rational Synthesis and Characterization of the Mixed-Metal Organometallic Polyoxometalates [Cp*MoxW6-xO18]- (x=0, 1, 5, 6)
    Taban-Çaliskan, G; Fernandes, DM; Daran, JC; Agustin, D; Demirhan, F; Poli, R
    The reaction between the oxometallic complexes Cp*2M2O5 and Na2M'O-4 (M, M' = Mo, W) in a 1:10 molar ratio in an acidic aqueous medium constitutes a mild and selective entry into the anionic Lindqvist-type hexametallic organometallic mixed oxides [Cp*MoxW6-xO18](-) [x = 6 (1), 5 (2), 1 (3), 0 (4)]. All of these compounds have been isolated as salts of nBu(4)N(+) (a), nBu(4)P(+) (b), and Ph4P+ (c) cations and two of them (1 and 3) also with the n-butylpyridinium (nBuPyr(+), d) cation. The compounds have been characterized by elemental analyses, thermogravimetric analyses, electrospray mass spectrometry, and IR spectroscopy. The molecular identity and geometry of compounds 1c, 2a, and 2c have been confirmed by single-crystal X-ray diffraction. Density functional theory calculations on models obtained by replacing Cp* with Cp (I-IV) have provided information on the assignment of the terminal M=O and bridging M-O-M vibrations.
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    Investigation of the reaction of [Cp*2M2O5](M = Mo, W) with hydrogen peroxide and tert-butylhydroperoxide in MeCN; implications for olefin epoxidation catalyzed by organomolybdenum and organotungsten compounds
    Bhaumik, C; Manoury, E; Daran, JC; Sözen-Aktas, P; Demirhan, F; Poli, R
    Compounds [Cp*2M2O5] (M Mo, W) react with stoichiometric amounts of H2O2 (as a 30% w/w solution in water) and (BuOOH)-Bu-t (TBHP, as a 70% w/w solution in decane) in MeCN solution to yield a variety of products as shown by the H-1 NMR monitoring of the Cp* resonance. The reaction rate increases in the order W < Mo and TBHP < H2O2. While the total Cp* intensity remains constant when using stoichiometric amounts of oxidant, use of excess oxidant results in the ultimate total Cp* loss. From the decomposed solutions, crystals of [Cp*2Mo6O17] (1), (C5Me5O)[Cp*M6O18] (M Mo, 2a; W, 2b), and (C5Me(5)O)(2)[Mo6O19] (3) were recovered and analyzed by X-ray diffraction. Catalytic cyclooctene epoxidation experiments with ((Bu4N)-Bu-n)(2)[M6O19] (M Mo, W) in a 3: 1 MeCN/toluene mixture at 55 degrees C using either aqueous H2O2 or TBHP/decane as oxidant revealed that these are not the active forms of the catalyst which is generated under the same conditions from [Cp*2M2O5], as reported in previous contributions from our group (Chem. Eur. J., 2010, 16, 9572e9584; Eur. J. Inorg. Chem., 2013, 2728e2735). Further catalytic studies using aged [Cp*2Mo2O5]/TBHP and [Cp*2W2O5]/H2O2 solutions show a small loss of activity (< 50% in one week) attesting the robustness of the non-organometallic catalytically active species that is generated from the decomposition of [Cp*2M2O5]. These results cast doubts on the role of cyclopentadienyl as a supporting ligand for stable olefin epoxidation catalysts. (C) 2013 Elsevier B. V. All rights reserved.
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    1-Ferrocenylmethyl-3-(2,4,6-trimethylbenzyl)-1H-imidazolidin-3-ium iodide and trans-bis(3-benzyl-1-ferrocenylmethyl-1H-imidazolidin-2-ylidene)diiodidopalladium(II)
    Daran, JC; Demirhan, F; Yildirim, Ö; Çetinkaya, B
    Owing to increasing interest in the use of N-heterocyclic carbenes (NHCs) based on imidazolidinium ions as ligands in the design of highly efficient transition-metal-based homogeneous catalysts, the characterizations of the 1-ferrocenylmethyl-3-(2,4,6-trimethylbenzyl)imidazolidin-3-ium iodide salt, [Fe(C5H5)(C19H24N2)]I, (I), and the palladium complex trans-bis(3-benzyl-1-ferrocenylmethyl-1H-imidazolidin-2-ylidene)diiodidopalladium(II), [Fe2Pd(C5H5)(2)(C16H17N2)(2)I-2], (II), are reported. Compound (I) has two iodide anions and two imidazolidinium cations within the asymmetric unit (Z' = 2). The two cations have distinctly different conformations, with the ferrocene groups orientated exo and endo with respect to the N-heterocyclic carbene. Weak C-H donor hydrogen bonds to both the iodide anions and the pi system of the mesitylene group combine to form two-dimensional layers perpendicular to the crystallographic c direction. Only one of the formally charged imidazolidinium rings forms a near-linear hydrogen bond with an iodide anion. Complex (II) shows square-planar coordination around the Pd-II metal, which is located on an inversion centre (Z' = 0.5). The ferrocene and benzyl substituents are in a trans-anti arrangement. The Pd-C bond distance between the N-heterocyclic carbene ligands and the metal atom is 2.036 (7) angstrom. A survey of related structures shows that the lengthening of the N-C bonds and the closure of the N-C-N angle seen here on metal complexation is typical of similar NHCs and their complexes.
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    Reaction of [Cp*2W2O5] with mercaptocarboxylic acids: Addition rather than reduction. Isolation and characterization of Cp*WO2(SCH2CH2COOH)
    Sözen, P; Daran, JC; Manoury, E; Demirhan, F; Poli, R
    The reaction of Cp*2W2O5 with HS(CH2) nCOOH (n - 1, 2) in MeOH or in CH2Cl2 solutions at room temperature proceeds in slightly different ways depending on the value of n. For n = 2, it selectively yields compound Cp*WO2(SCH2CH2CO2H), which has been isolated and characterized by elemental analysis, NMR and single crystal X-ray diffraction. The reaction is equilibrated, being shifted to the product by absorption of water by anhydrous Na2SO4 in CH2Cl2, and to the reactants by addition of water. Contrary to the Mo analogue, no products resulting from metal reduction are obtained. The corresponding reaction for n = 1 occurs similarly at low substrate/W ratios (< 0.5), but proceeds further to several uncharacterized products for greater substrate amounts. The primary product could not be isolated, but its H-1 NMR spectrum suggests a different, asymmetric structure. (C) 2010 Elsevier B.V. All rights reserved.
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    Aqueous reduction of [Cp*2W2O51]: Characterization of the triangular clusters [Cp*3W3O4(OH)2]2+ and [Cp*3W3O6]+ - Comparison with molybdenum
    Dinoi, C; Sözen, P; Taban, G; Dernir, D; Demirhan, F; Prikhodchenko, P; Gun, J; Lev, O; Daran, JC; Poli, R
    Zinc reduction Of CP * 2W2O5 in an acidified water-methanol medium affords the green 3-electron trinuclear cluster [CP*3W3O4(OH)(2)](+2), isolated and crystallographically characterized as the triflate salt, 1. Upon exposure to air, this complex is oxidized to a related 2-electron cluster, [Cp * 3W3O6], which was crystallized and characterized in three different salts, 2-4. The 3-electron cluster exhibits a near-tetragonal frozen-glass EPR spectrum, and it shows evidence of coupling of the unpaired electron to only one of the three W atoms. The two-electron cluster is diamagnetic. An electro-spray ionization MS' study revealed a stepwise expulsion of neutral [CP*WO2] units as the main fragmentation process. DFT calculations unveiled the intimate details of the electronic structures of these complexes and fully rationalized the structural and spectroscopic properties.
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    Synthesis, structure, electrochemical and antimicrobial properties of N,N′-bis(ferrocenylmethyl)imidazolinium salts
    Özbek, HA; Aktas, PS; Daran, JC; Oskay, M; Demirhan, F; Çetinkaya, B
    The N, N'-bis(ferrocenylmethyl)imidazolinium chloride (3) and bromide (4) were prepared by reaction of N,N'-bis(ferrocenylmethyl)ethylenediamine (2) with NH4X (X = Cl, Br). The N,N'-bis(ferrocenylmethyl)imidazolinium tetrafluoroborate (6) was obtained in two steps from compound (2). The first step involves the synthesis of N,N'-bis(ferrocenylmethyl)imidazolidine (5) by condensation of (2) with aqueous formaldehyde. Compound (5) was successfully converted to the N,N'-bis(ferrocenylmethyl)imidazolinium tetrafluoroborate (6) by treatment with tritylium tetrafluoroborate. The new compounds were characterized by H-1 and C-13 NMR, IR and elemental analysis techniques which support the proposed structures. The X-ray crystal structure of the N,N'-bis(ferrocenylmethyl)imidazolidine (5) shows two ferrocenyl moieties bridged by an imidazolidine ring. The electrochemical properties were determined by cyclic voltammetry for all compounds. The compounds were screened for their in vitro antimicrobial activities against the Gram-positive, Gram-negative bacteria and antifungal activity against a Candida albicans. (3), (4), (6) show significant antimicrobial activity and theirs MIC values ranged from 169 to 520 mu g/mL. (C) 2014 Elsevier B.V. All rights reserved.
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    Improved syntheses Of [CP*2Mo2O5] and [CP*2W2O5]: Structural characterization of Na[Cp*MoO3].5H2O and [CP*2W2O5]
    Dinoi, C; Taban, G; Sözen, P; Demirhan, F; Daran, JC; Poli, R
    Use of aqueous conditions and the ROOH (R = tBu or H) compounds as oxidizing agents affords a simple two-step, one-pot synthetic procedure leading to [Cp*2M2O5] W = Mo, W) from [M(CO)(6)] selectively and in high yields. The hexacarbonyl compounds are converted to Na[Cp*M(CO)(3)] in refluxing THF, then the mixture is diluted with water (W) or aqueous NaOH (Mo) and directly treated with 6 equiv. of ROOH. Acidification of an aqueous solution of the Na[Cp*MO3] product affords spectroscopically pure [Cp2M2O5] in high isolated yields (global yields from [M(CO)(6)], for R = tBu: Mo, 91%; W, 87%). The X-ray structures of Na[Cp*MoO3].5H(2)O and [Cp*2W2O5] are also reported. (c) 2007 Elsevier B.V. All rights reserved.