- Electrochemical studies of protonation reaction of anion radicals of some dinitroaromatics in dichloromethane
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Protonation of anion radicals of 1,2-,1,3- and 1,4-dinitrobenzenes in dichloromethane in the temperature range 0, 5, 10 and 15 °C has been investigated by cyclic voltammetric method. Glassy carbon electrode and hanging mercury drop electrode are used as working electrodes. Benzoic acid and salicylic acid are used as protonating agents. Homogeneous rate constant is calculated by using Nicholson and Shain equation. The position of nucleophilic attack in dinitrobenzenes has been investigated by calculation of charge densities using MNDO and SCF-UHF molecular orbital methods. The heterogeneous rate constant ks,h for the first reduction process in dinitrobenzenes is determined by digital simulation of the cyclic voltammograms.
- Hanif, Farzana,Yasmeen, Ghazala,Manzoor, Suryyia,Aamir, Muhammad
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- Mitochondria targeting photocytotoxic oxidovanadium(IV) complexes of curcumin and (acridinyl)dipyridophenazine in visible light
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Oxidovanadium(IV) complexes, [VO(acac)(L)Cl] (1), [VO(cur)(L)Cl] (2), and [VO(scur)(L)Cl] (3) {acac = acetylacetonate, cur = curcumin monoanion, scur = diglucosylcurcumin monoanion, L = 11-(9-acridinyl)dipyrido[3, 2-a:2',3'-c]phenazine (acdppz)}, were prepared and characterized. The complexes are non-electrolytic in DMF and 1:1 electrolytic in aqueous DMF. The one-electron paramagnetic complexes showed a d-d band near 725 nm in aqueous DMF and green emission near 520 nm in aqueous DMSO. The complexes exhibited an irreversible VIV/VIII redox response near-0.85 V versus SCE in aqueous DMF. The complexes showed good binding strengths to calf thymus DNA (Kb: 3.1×105-9.6×105 M -1) and efficient pUC19 DNA photocleavage activity in red light of 705 and 785 nm by singlet oxygen (1O2) pathway. Complexes 1 and 2 exhibited significant photocytotoxicity (IC50: 0.1-1.0 μM) in visible light (400-700 nm) with low dark toxicity (IC 50: >20 μM) in HeLa and HaCaT cells. Complex 3 was cytotoxic in both light and dark. DNA ladder formation experiments indicated cell death via apoptotic pathway. Confocal microscopy done with 1 and 2 revealed primarily cytosolic localization of the complexes with significant presence of the complex in the mitochondria as evidenced from the imaging data using mitotracker red. Copyright
- Banerjee, Samya,Prasad, Puja,Khan, Imran,Hussain, Akhtar,Kondaiah, Paturu,Chakravarty, Akhil R.
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- Curcumin "drug" Stabilized in Oxidovanadium(IV)-BODIPY Conjugates for Mitochondria-Targeted Photocytotoxicity
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Ternary oxidovanadium(IV) complexes of curcumin (Hcur), dipicolylamine (dpa) base, and its derivatives having pendant noniodinated and di-iodinated boron-dipyrromethene (BODIPY) moiety (L1 and L2, respectively), namely, [VO(dpa)(cur)]ClO4 (1), [VO(L1)(cur)]ClO4 (2), and [VO(L2)(cur)]ClO4 (3) and their chloride salts (1a-3a) were prepared, characterized, and studied for anticancer activity. The chloride salts were used for biological studies due to their aqueous solubility. Complex 1 was structurally characterized by single-crystal X-ray crystallography. The complex has a VO2+ moiety bound to dpa ligand showing N,N,N-coordination in a facial mode, and curcumin is bound in its mono-anionic enolic form. The V-O(cur) distances are 1.950(18) and 1.977(16) ?, while the V-N bond lengths are 2.090(2), 2.130(2), and 2.290(2) ?. The bond trans to V=O is long due to trans effect. The complexes are stable in a solution phase over a long period of time of 48 h without showing any apparent degradation of the curcumin ligand. The diiodo-BODIPY ligand (L2) or Hcur alone showed limited solution stability in dark. The emissive BODIPY (L1) containing complex 2a showed preferential mitochondrial localization in MCF-7 cells in cellular imaging experiments. The cytotoxicity of the complexes was studied by MTT assay. The BODIPY complex 3a showed excellent photodynamic therapy effect in visible light (400-700 nm) giving IC50 values of 2-6 μM in HeLa and MCF-7 cancer cells, while being less toxic in dark (～100 μM). The cell death was apoptotic in nature involving reactive oxygen species (ROS). Mechanistic data from pUC19 DNA photocleavage studies revealed photogenerated ROS as primarily 1O2 from the BODIPY moiety and ·OH radicals from the curcumin ligand.
- Bhattacharyya, Utso,Kumar, Brijesh,Garai, Aditya,Bhattacharyya, Arnab,Kumar, Arun,Banerjee, Samya,Kondaiah, Paturu,Chakravarty, Akhil R.
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- The cis-Diammineplatinum(II) Complex of Curcumin: A Dual Action DNA Crosslinking and Photochemotherapeutic Agent
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[Pt(cur)(NH3)2](NO3) (1), a curcumin-bound cis-diammineplatinum(II) complex, nicknamed Platicur, as a novel photoactivated chemotherapeutic agent releases photoactive curcumin and an active platinum(II) species upon irradiation with visible light. The hydrolytic instability of free curcumin reduces upon binding to platinum(II). Interactions of 1 with 5′-GMP and ct-DNA indicated formation of platinum-bound DNA adducts upon exposure to visible light (λ=400-700 nm). It showed apoptotic photocytotoxicity in cancer cells (IC50≈15 μM), thus forming OH, while remaining passive in the darkness (IC50>200 μM). A comet assay and platinum estimation suggest Pt-DNA crosslink formation. The fluorescence microscopic images showed cytosolic localization of curcumin, thus implying possibility of dual action as a chemo- and phototherapeutic agent.
- Mitra, Koushambi,Gautam, Srishti,Kondaiah, Paturu,Chakravarty, Akhil R.
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- Efficient method for varying the anions in quaternary onium halides
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Quaternary onium salts of halides can be efficiently converted into the corresponding quaternary onium salts of various anions [NO3 -, BF4-, PF6-, CF 3SO3-, CH3SO3 -, ClO4-, p-CH3C6H 4SO3-, CF3CO2 -, 2,4-(NO2)2C6H3O -] by treating the onium halide with trimethyl phosphate under neat condition in the presence of an equivalent amount of conjugate acid of the desired anion.
- Jeon, Jong Yeob,Varghese, Jobi Kodiyan,Park, Ji Hae,Lee, Suck-Hyun,Lee, Bun Yeoul
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experimental part
p. 3566 - 3569
(2012/08/14)
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- Conductivity and dissociation constants of quaternary ammonium perchlorates and picrates in 4-methyl-pentan-2-one
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The dissociation of 14 ionophores, namely, seven symmetrical (C1 to C7) and five asymmetrical quaternary ammonium perchlorates and two tetraalkylammonium picrates (all with linear hydrocarbon chains), in 4-methyl-pentan-2-one was studied at 25 °C (εr = 12.92) using the conductance method. The values of the association constants of the quaternary ammonium cation, Ct+, with ClO4- vary from (7.4 ± 0.3) ·103 L·mol-1 for tetramethylammonium to (2.4 ± 0.1) ·103 L·mol-1 for tetrahexyl- and tetraheptylammonium; a distinct dependence on the size of the Ct+, especially for symmetrical cations, is evident. The values of the limiting molar conductivities Λ0/S·mol-1·cm2 vary from 122.8 to 90.0 (± 0.7). The plot of Λ0 versus the reciprocal cube root of the total van der Waals volume of the cations, V Ct-1/3, is close to linear up to tetrapentylammonium and hexadecyltrimethylammonium, while for larger cations (with 21 to 28 carbon atoms) the Λ0 values stay practically constant. At the same time, symmetrical and asymmetrical cations with the same VCt values possess equal mobility.
- Goga, Sergey T.,Lebed, Alexander V.,McHedlov-Petrossyan, Nikolay O.
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body text
p. 1887 - 1892
(2011/07/30)
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- Replacement of imidazoles by azide at an iron(III) porphyrin center: Part 1 replacement of N-methylimidazole in bis-(N-methylimidazole) tetraphenylporphyrinato iron(III)
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Addition of tetra-n-butylammonium azide to acetone solutions of the tetraphenylporphyrinato iron(III) complex [Fe(TPP)(MeIm)2] +N-3 formed in situ from the reaction of N-methylimidazole and [Fe(TPP)N3] afforded equilibrium amounts of [Fe(TPP)(MeIm)2]+ and [Fe(TPP)(MeIm)N3]. Equilibrium experiments made using a range of known concentrations of added tetra-n-butylammonium azide and N-methylimidazole using stopped-flow apparatus gave an estimate of about 50 for the equilibrium constant for the formation of [Fe(TPP)(MeIm)N3] from the addition of azide to [Fe(TPP)(MeIm) 2]+. Kinetic studies indicated that the substitution of azide ion by N-methylimidazole is a dissociative process, and the results were interpreted using a stationary state approach in which [Fe(TPP)(MeIm)] + was the transient intermediate that discriminated in favor of the reaction with azide as opposed to the reaction with N-methylimidazole by about a factor of two. Loss of N-methylimidazole from [Fe(TPP)(MeIm)2] + is at least 50 times faster than that from the product [Fe(TPP)(MeIm)N3]. Using calculated values of free azide concentrations from experimentally determined ion-pair formation constants led to success in rationalizing results obtained under different conditions.
- Jones, John G.,McKnight, John,Twigg, Martyn V.
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experimental part
p. 2766 - 2778
(2010/12/25)
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- PHOTOCHEMICAL AND ELECTROCHEMICAL PROPERTIES OF THE COMPLEXES cis-
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The complexes cis-, (where N2O2 = tetradentate dianionic open-chain ligands of acacen, salen or benacen-type; acac = 2,4-pentadionate anion) undergo photoredox reactions under the influence of ultraviolet radiation giving rise to Co(II).The quantum yield values of the Co(III) reduction, associated with the oxidation of the acac ligand, depend on the periphery (substituents R) of the N2O2-ligands and the wavelength of incident light.The complexes are luminescent from their intraligand excited states.In acetonitrile solution the complexes exhibit an electrochemical oxidation response (Epa : 0.86 to 1.02 V vs SCE) of primarily ligand oxidation origin.A linear correlation has been obtained between the anodic peak potential, Epa and the inductive parameter, ?/ of the substituents R.The electrochemical reduction of the complexes was poorly resolved or missing within the solvent limit.
- Sima, J.,Kotocova, A.,Germuska, R.,Kubat, P.,Engst, P.
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- Neutral and Anionic Binuclear Perhalogenophenyl Platinum-Silver Complexes with Pt->Ag Bonds Unsupported by Covalent Bridges. Molecular Structures of , and (tht = tetrahydrothiophene)
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Heterobinulear complexes of general formula 14-21 have been prepared by treating the anionic platinum derivatives with (molar ratio 1:1) in dichloromethane.The anionic (L = OEt2, PPh3 or tht) 22-24 and 25 have been obtained from the corresponding 2 and (molar ratio 1:1) in CH2Cl2-diethyl ether.The reaction between and renders Ag(C6F5) and cis-.The salts 2 and 24> react with yielding and , respectively.The reactions between 2 and or (molar ratio 1:2) render in the first case complex 24 while in the second an unstable material which evolves to 27 is obtained. The reaction between 2 (X = F or Cl) and or ClO4 have also been studied.The structures of 14, 24 and 25 have been established by single-crystal X-ray diffraction studies.The complexes contain a strong Pt->Ag bond unsupported by covalent bridges, and short contacts between the o-F or o-Cl atoms of the C6X5 (X = F or Cl) groups and the Ag atom are present.The relative strength of such contacts is discussed.Methods for the synthesis of mixed pentachloro-pentafluorophenyl starting complexes 1-13 have been investigated.
- Uson, Rafael,Fornies, Juan,Tomas, Milagros,Ara, Irene,Casas, Jose M.,Martin, Antonio
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p. 2253 - 2264
(2007/10/02)
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- Bi- and trinuclear PtAg complexes with or without Pt-Ag bonds. Molecular structure of [PPh3(C6Cl5)ClPt(μ-Cl)AgPPh3]
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When (NBu4)2[trans-PtCl2(C6Cl 5)2] is reacted with O3ClOAgL (L = PPh3, PEt3; molar ratio 1:1), the binuclear (NBu4)[PtAgCl2(C6Cl5)2L] (L = PPh3 (I), PEt3 (II)) complexes are obtained, while, for L = PPh2Me, the trinuclear [Pt(C6Cl5)2{(μ-Cl)AgL}2] (III) is obtained in low yield. The trinuclear complexes with L = PPh2Me (III, in higher yield), L = PPh3 (IV), and L = PEt3 (V) are obtained when the above-mentioned reactions are carried out in a 1:2 molar ratio. (NBu4)[trans-PtCl2(C6Cl5)L] reacts with O3ClOAgL′ (molar ratio 1:1 or 1:2), yielding the novel binuclear derivatives [L(C6Cl5)ClPt(μ-Cl)AgL′] (L′ = PPh3, L = PPh3 (VI), SC4H8 (VII), NC5H5 (VIII); L′ = PPh2Me, L = PPh3 (IX)). The structure of VI has been solved by single-crystal X-ray diffraction. The compound crystallizes in the monoclinic system, space group P21/n, with a = 14.270 (2) A?, b = 14.663 (2) A?, c = 20.024 (2) A?, β = 93.58 (1)°, V = 4181.69 A?3, and Z = 4. The structure was refined to residuals of R = 0.037 and Rw = 0.037. The "PtCl2(C6Cl5)PPh3" and "AgPPh3" fragments are bonded by a single chlorine bridge, Pt(μ-Cl)Ag (Pt-Cl1 = 2.341 (3) A?, Ag-Cl1 = 2.514 (2) A?), and a weak Pt-Ag bond (Pt-Ag = 2.945 (1) A?), and two [(PPh3)(C6Cl5)ClPt(μ-Cl)Ag(PPh3)] units are connected through a weak Ag′-Cl1 interaction (Ag′?Cl1 = 3.023 (2) A?). The silver atom makes a short contact with one o-chlorine atom of the C6Cl5 groups (Ag?C17 = 3.041 (4) A?).
- Usón, Rafael,Forniés, Juan,Tomás, Milagros,Ara, Irene,Casas, José M.
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p. 2388 - 2392
(2008/10/08)
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- Synthesis and Reactivity of Trinuclear Complexes of Platinum containing the Single Bridging Ligand SC4H8. Molecular Structure of 2
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Trinuclear complexes of the type 2 (X = Cl, Br, I, or C6F5; SC4H8 = tetrahydrothiophene) (1)-(4) have been prepared from trans- and NBu4 (molar ratio 1:2).The SC4H8 ligands act as the single bridge between the central platinum atom and the two terminal ones.Attempts to prepare similar trinuclear complexes with singly bridging halide ligands failed since the reaction between trans- (py = pyridine) and NBu4 (molar ratio 1:2) does not take place, while trans- or (cod = cyclo-octa-1,5-diene), under similar conditions, yield cis- and 2 or and 2 respectively.The trinuclear derivatives (1) and (3) react with neutral ligands L to give different mononuclear complexes, depending on the ligand L: when L = PPh3, NBu4 and cis-; when L = CO, NBu4 and trans-.The molecular stucture of 2 has been established by a single-crystal X-ray diffraction study.The compound forms triclinic crystals in the space group P1/, with Z = 1 and unit-cell dimensions a = 12.463(3), b = 12.487(3), c = 15.137(3) Angstroem, α = 85.68(15), β = 66.04(2), and γ = 87.04(1) degree.The structure was refined to R = 0.048 and R' = 0.048.The central platinum atom in the trinuclear anion (2-) lies on a crystallographic centre of symmetry and is bonded to two Cl atoms and two S atoms (from two SC4H8 ligands), the latter acting as bridging ligands between the central and the terminal Pt atoms.
- Uson, Rafael,Fornies, Juan,Tomas, Milagros,Ara, Irene
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p. 1011 - 1016
(2007/10/02)
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- Synthesis of Pentafluorophenyl(ylide)silver(I) Complexes: X-Ray Structures of two Modifications of
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Monomeric silver ylide complexes (ER3=PPh3, PPh2Me, PPhMe2, or AsPh3) can be prepared by the reaction of Ag(CF3CO2) with Li(C6F5) and .The free ylides CH2PPh3, CH2PPh2Me, or CH(CO2Me)PPh3 react with Ag(C6F5) or AgClO4 to afford or ClO4 respectively.Several novel ylide-transfer reactions from silver ylides to other silver or gold centres are reported.The structures of two forms of have been established.The molecules differ mainly in the orientation of one phenyl ring.The C6F5 groups are highly distorted at the ipso carbon .
- Uson, Rafael,Laguna, Antonio,Uson, Alfredo,Jones, Peter G.,Meyer-Baese, Karen
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p. 341 - 346
(2007/10/02)
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- Tetranuclear homo- or heterobimetallic asymmetric palladium(II)-platinum(II) complexes with single halide bridges. Molecular structure of [Pt(C6F5)2(μ-Br)Pd(η 4-1,5-C8H12)(μ-Br)Pt(C6F 5)2(μ-Br)Pd-(η4-1,5-C8H 12)(μ-Br)]
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Treatment of cis-[M(C6X5)2(THF)2] (M = Pd, Pt; X = F, Cl; THF = tetrahydrofuran) with M′X′2(COD) (M′ = Pd, Pt; X′ = Cl, Br, I; COD = 1,5-cyclooctadiene) results in the formation of homo- and heteronuclear palladium or platinum complexes of general formula [(C6X5)2M(μ-X′) 2M′(COD)]n which are binuclear (n = 1) in CHCl3 solutions. The molecular structure of [Pt(C6F5)2(μ-Br)Pd(COD)(μ-Br)Pt(C 6F5)2(μ-Br)-Pd(COD)(μ-Br)] has been established by single-crystal X-ray crystallography, showing that the complex is tetranuclear in the solid state. The molecule resides on a center of symmetry and can be regarded as an eight-membered ring skeleton being made up of two Pt(C6F5)2 and two Pd(η4-1,5-C8H12) groups in an alternate way connected by single bromide bridges. Crystal data: monoclinic, a = 26.742 (6) A?, b = 9.3916 (18) A?, c = 18.133 (5) A?; β = 108.424 (22)°; space group C2/c; Z = 4. The structure has been solved from diffractometer data by direct and Fourier methods and refined by full-matrix least squares to R = 0.0369 for 3059 observed reflections.
- Usón,Forniés,Tomás,Menjón,Welch
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p. 1318 - 1323
(2008/10/08)
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- Synthesis, X-ray structure, and reactivity of (NBu4)2[Pt2(μ-C5F 5)2(6F5)4]·H 2O and (NBu4)[Pt2Ag(μ-C6F5) 2(C6F5)4O(C2H 5) ...
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Full title: Synthesis, X-ray structure, and reactivity of (NBu4)2[Pt2(μ-C5F 5)2(6F5)4]·H 2O and (NBu4)[Pt2Ag(μ-C6F5) 2(C6F5)4O(C2H 5)2]. The first complexes containing bridging pentafluorophenyl groups. By reacting (NBu4)2[Pt(C6F5)3Cl] with AgClO4 (molar ratio 1:1) in CH2Cl2/diethyl ether, the binuclear complex (NBu4)2[Pt2(μ-C6F 5)2(C6F5)4] (1) is obtained. (NBu4)[Pt2Ag(μ-C6F5) 2(C6F5)4]·O(C 2H5)2 (2) can be prepared by reacting 1 with AgClO4 (molar ratio 1:1) or by treating (NBu4)2[Pt(C6F5)3Cl] with AgClO4 (molar ratio 1:2) in CH2Cl2/diethyl ether. Complex 2 reacts with neutral monodentate ligands (L) yielding (NBu4)[Pt2Ag(μ-C6F5) 2(C6F5)4L] (L = PPh3, 3; L = CNCy, 4). The structures of the binuclear platinum complex 1 and the trinuclear Pt2Ag complex 2 have been solved by single-crystal X-ray diffraction. Complex 1 contains the platinum atoms bridged by pentafluorophenyl groups (Pt-Pt distance = 2.714 (1) A?). Complex 2 contains two Pt-Ag bonds unsupported by other covalent bridges (Pt-Ag distances = 2.815 (2) and 2.804 (2) A?. The platinum atoms (Pt-Pt distance = 2.687 (1) A?) are bridged by two pentafluorophenyl groups and one silver atom.
- Uson, Rafael,Fornies, Juan,Tomas, Milagros,Casas, Jose M.,Albert Cotton,Falvello, Larry R.,Llusar, Rosa
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p. 2279 - 2285
(2008/10/08)
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- Assoziationverhalten und Dipolmomente von Tetra(n-Butyl)Ammoniumpertechnetat und Tetra(n-Butyl)Ammoniumperchlorate in Benzol
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At very low concentrations tetra-n-butylammonium pertechnetate and tetra-n-butylammonium perchlorate form ion pairs in benzene solutions.At room temperature, formation of dimers and lager aggregates begins to occur at concentrations of 1E-5 mol/l.This behaviour has been investigated quantitatively by the determination of the molecular weight in the case of the perchlorate salt, and by the concentration-dependence of the pertechnetate phase equilibrium between water and benzene.It could be demonstrated that Bu4NTcO4-dimers and larger aggregates have no apparent dipole moment.Knowing the relative concentration of the monomers from the extraction experiments, the dipole moment of 16.6 Debye has been calculated for the ion pair.Applying an extrapolation method, the dipole moment of Bu4NClO4 was found to be 16.2 Debye.The similarity of the dipole moments is in good agreement with the similar ionic radii of the TcO4(-) and the ClO4(-) ions.The charge separation in the ion pairs however, calculated from the dipole moments, is smaller than the sum of cationic and anionic radii. - Key words: Association Behaviour / Dipole Moments / Ion Pairs / Tetrabutylammonium Salts
- Neck, Volker,Maier, Ralph,Kanellakopulos, Basil
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p. 123 - 127
(2007/10/02)
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- USE OF NAFION MEMBRANES IN LABORATORY ORGANIC ELECTROSYNTHESIS
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Electrolysis of quarternary ammonium bromides and iodides in a divided cell with a Nafion membrane yields quarternary polyhalogenides at a carbon anode in water-ethanolic anolytes.The electrodialysis of tetrabutylammonium iodide in a cell with a Nafion membrane enables generation of tetrabutylammonium hydroxide.In electrolytic reduction of nitrobenzene in presence of 1,3-dibromopropane, N-phenylisoxazolidine results in approx. 60percent yield.This electrosynthesis takes place in dimethylformamide with tetrabutylammonium bromide at a glassy-carbon cathode in a divided cell.In the electroreduction of lobelanine hydrogensulfate in a divided cell in acid water-ethanolic media at a lead cathode prevalently lobelanidine has been obtained.
- Hlavaty, Jaromir,Volke, Jiri
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p. 3164 - 3170
(2007/10/02)
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- Infrared Spectroscopic Studies of Hydrogen Bonding in Triethylammonium Slats. Part 4. Rearrangement of Hydrogen-bonded Ion Pairs of Triethylammonium Salts caused by Interaction with Tetrabutylammonium Salts in Solution
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Rearrangement of triethyl- and tetrabutylammonium salts in chloroform solution has been revealed from the characteristic features of the ν(N+H) bands caused by Fermi resonance interaction.Temperature changes of the i.r. spectra show this process to be reversible.Rearrangement constant K1 and K-1 and enthalpies -ΔH (for some cases only) of this process have been determined by measuring the total integrated intensities of the ν(N+H) bands of complexes which are in equilibrium.K1 values of the tetrabutylammonium salts increase with decreasing hydrogen bonding strength in triethylammonium salts.The measured enthalpies of rearrangement and those calculated from the ν(N+H) bands of hydrogen-bonded complexes studied are in agreement.It has also been shown that tetrabutylammonium salts anions can participate in the rearrangement of hydrogen-bonded ion pairs like the organic bases studied previously.
- Mashkovsky, Alexander A.,Nabiullin, Ahat A.,Odinokov, Stanislav E.
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p. 1879 - 1884
(2007/10/02)
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- UNE METHODE SIMPLE DE SYNTHESE DES PHOSPHATES TERPENIQUES ALLYLIQUES PRIMAIRES ET TERTIAIRES.
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Alkylation of tetrabutylammonium dihydrogenophosphate by terpenic allylic sulphonium salts give the corresponding primary terpenic allylic phosphates in fair to moderate yields, without complex procedures of purification.The catalysis of the reaction by cuprous ion leads to the isolation of tertiary allylic phosphates.
- Julia, M,Mestdagh, H.,Rolando, C.
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p. 3841 - 3850
(2007/10/02)
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- Synthesis and Reactivity of Bimetallic Au-Ag Polyfluorophenyl Complexes; Crystal and Molecular Structures of n> and n>
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The reaction of n4> (R=C6F5 or C6F3H2-2,4,6) with Ag leads to complexes n>, which react with neutral ligands to give complexes n> (L=neutral O-, N-, S- or P-donor ligand, alkene, or alkyne).For R=C6F5 and L=diphenylacetylene, the product is n>; the 0.5L can be displaced by other ligands, such as acetone, arenes, or alkenes, to reform n>.An X-ray diffraction study of n> (R=C6F5, L=tetrahydrothiophene) reveals (AuAg)2 rings with Au-Ag 2.726 and 2.718 Angstroem (the first reported Au-Ag bond lengths), linked by Au...Au short contacts (2.889 Angstroem) to form infinite metal-atom chains.This complex crystallizes in space group Pccn, with a=11.185(3), b=22.475(6), c=14.802(4) Angstroem, Z=8, R=0.041 for 2 005 reflections.The complex n> (R=C6F5, L=benzene) crystallizes in space group C2/c, with a= 24.231(5), b=7.570(1), c=22.613(5) Angstroem, β=117.49(2) deg, Z=8, and R=0.035 for 3 008 reflections; it shows the same type of metal-atom chain (Au...Au 3.013; Au-Ag 2.702 and 2.792 Angstroem).The benzene ring is co-ordinated by one edge to silver.In both structures the gold atoms lie on a crystallographic two-fold axis.
- Uson, Rafael,Laguna, Antonio,Laguna, Mariano,Manzano, Blanca R.,Jones, Peter G.,Sheldrick, George M.
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p. 285 - 292
(2007/10/02)
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