- Systematics of the Formation of Π-CO Ligands in Four-Iron Clusters. Synthesis and Structures of *CH2Cl2, Fe4(AuPet3)(CO)12(COCH3), , and
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The Lewis acid ligands (1+), (1+), and (1+) interact with the metal framework of the tetrahedral iron cluster (2-).In all cases, two products result, one of which consists of the Fe4 tetrahedron with the Lewis acid capping one face.The other more novel product is a Fe4 butterfly array with the Lewis acid ligand on the hinge and a Π-CO between the wingtips.By proper choice of counterion and conditions, either the butterfly or tetrahedral form can be crystallized.X-ray structures were determined for representative compounds of both products in this series.Tetrahedral iron frameworks were observed for (5a) and (6(tetrahedron)).Both *CH2Cl2 (3a) and Fe4(AuPEt3)(CO)12(COCH3) (7) have butterfly iron cores.Butterfly complexes such as 3a display a characteristic and unique low-frequency Π-CO stretch in the 1380-1430-cm-1 region of the IR spectrum.Additionally, NMR spectra of the individual isomers were obtained by dissolving the pure crystalline material at -80 deg C and obtaining the spectrum at this temperature.The NMR spectra obtained in this manner were consistent with both IR spectra of the solid and the structure determined by X-ray crystallography.
- Horwitz, Colin P.,Holt, Elizabeth M.,Brock, Carolyn P.,Shriver, Duward F.
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- Radical Cations of Dialkylmercury Derivatives, Radiation Synthesis and Electron Spin Resonance Detection
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Exposure of very dilute solutions of Hg(CD3)2 in tetrachloromethane to 60Co γ-rays at 77 K gave a species whose e.s.r. spectrum is characteristic of the parent cation.Interpretation of the g-values and 199Hg tensor component B derived from a computer synthesis of the spectrum suggests that the unpaired electron is strongly confined to the linear ? orbital having a node through the mercury atom.This has a large 6p(Hg) character.No extra features were obtained using Hg(13CH3)(CH3), confirming that the spin density on the CH3 groups is small (19F).The spectra for Hg(CH3)2 in this solvent were analysed in terms of the same solvent features together with coupling to a least five and probably seven protons.The small 1H coupling was almost isotropic at +/-4.5 G.In contrast, Hg(C2H5)2 gave no resolved coupling to 19F, but there was a large, well defined, triplet splitting (42 G) assigned to two specific CH3 protons.This suggests that rotation about the C-C bonds is restricted.We were unable to detect free rotation on annealing, although the lines broadened considerably, prior to radical loss.Attempts to detect .CH3 or .CH2CH3 radicals in these systems were unsuccessful, but clear evidence for .CD3 radicals was obtained for Hg(CD3)2 in CFCl3 on annealing.
- Hasegawa, Akinori,Rideout, Jan,Symons, Martyn C.R.
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- Cleavage of Hg-C Bonds of Organomercurials Induced by ImOHSe via Two Distinct Pathways
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We show that the N-methylimidazole-based selone ImOHSe having an N-CH2CH2OH substituent has the remarkable ability to degrade methylmercury by two distinct pathways. Under basic conditions, ImOHSe converts MeHgCl into biologically inert HgSe nanoparticles and Me2Hg via the formation of an unstable intermediate (MeHg)2Se (pathway I). However, under neutral conditions, in the absence of any base, ImOHSe facilitates the cleavage of the Hg-C bond of MeHgCl at room temperature (23 °C), leading to the formation of a stable cleaved product, the tetracoordinated mononuclear mercury compound (ImOHSe)2HgCl2 and Me2Hg (pathway II). The initial rate of Hg-C bond cleavage of MeHgCl induced by ImOHSe is almost 2-fold higher than the initial rate observed by ImMeSe. Moreover, we show that ImYSe (Y = OH, Me) has an excellent ability to dealkylate Me2Hg at room temperature. Under acidic conditions, in the presence of excess ImYSe, the volatile and toxic Me2Hg further decomposes to the tetracoordinated mononuclear mercury compound [(ImYSe)4Hg]2+. In addition, the treatment of ImOHSe with MeHgCys or MeHgSG in phosphate buffer (pH 8.5) afforded water-soluble Hg(SeS) nanoparticles via unusual ligand exchange reactions, whereas its derivative ImOMeSe or ImMeSe, lacking the N-CH2CH2OH substituent, failed to produce Hg(SeS) nanoparticles under identical reaction conditions.
- Banerjee, Mainak,Roy, Gouriprasanna
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supporting information
p. 12739 - 12750
(2017/11/14)
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- Protection of Endogenous Thiols against Methylmercury with Benzimidazole-Based Thione by Unusual Ligand-Exchange Reactions
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Organomercurials, such as methylmercury (MeHg+), are among the most toxic materials to humans. Apart from inhibiting proteins, MeHg+ exerts its cytotoxicity through strong binding with endogenous thiols cysteine (CysH) and glutathione (GSH) to form MeHgCys and MeHgSG complexes. Herein, it is reported that the N,N-disubstituted benzimidazole-based thione 1 containing a N?CH2CH2OH substituent converts MeHgCys and MeHgSG complexes to less toxic water-soluble HgS nanoparticles (NPs) and releases the corresponding free thiols CysH and GSH from MeHgCys and MeHgSG, respectively, in solution by unusual ligand-exchange reactions in phosphate buffer at 37 °C. However, the corresponding N-substituted benzimidazole-based thione 7 and N,N-disubstituted imidazole-based thione 3, in spite of containing a N?CH2CH2OH substituent, failed to convert MeHgX (X=Cys, and SG) to HgS NPs under identical reaction conditions, which suggests that not only the N?CH2CH2OH moiety but the benzimidazole ring and N,N-disubstitution in 1, which leads to the generation of a partial positive charge at the C2 atom of the benzimidazole ring in 1:1 MeHg-conjugated complex of 1, are crucial to convert MeHgX to HgS NPs under physiologically relevant conditions.
- Banerjee, Mainak,Karri, Ramesh,Chalana, Ashish,Das, Ranajit,Rai, Rakesh Kumar,Rawat, Kuber Singh,Pathak, Biswarup,Roy, Gouriprasanna
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supporting information
p. 5696 - 5707
(2017/04/28)
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- Exchange of alkyl and tris(2-mercapto-1-t-butylimidazolyl)hydroborato ligands between zinc, cadmium and mercury
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Abstract The tris(2-mercaptoimidazolyl)hydroborato ligand, [TmBut], has been used to investigate the exchange of alkyl and sulfur donor ligands between the Group 12 metals, Zn, Cd and Hg. For example, [TmBut]2Zn reacts with Me2Zn to yield [TmBut]ZnMe, while [TmBut]CdMe is obtained readily upon reaction of [TmBut]2Cd with Me2Cd. Ligand exchange is also observed between different metal centers. For example, [TmBut]CdMe reacts with Me2Zn to afford [TmBut]ZnMe and Me2Cd. Likewise, [TmBut]HgMe reacts with Me2Zn to afford [TmBut]ZnMe and Me2Hg. However, whereas the [TmBut] ligand transfers from mercury to zinc in the methyl system, [TmBut]HgMe/Me2Zn, transfer of the [TmBut] ligand from zinc to mercury is observed upon treatment of [TmBut]2Zn with HgI2 to afford [TmBut]HgI and [TmBut]ZnI. These observations demonstrate that the phenomenological preference for the [TmBut] ligand to bind one metal rather than another is strongly influenced by the nature of the co-ligands.
- Kreider-Mueller, Ava,Quinlivan, Patrick J.,Rong, Yi,Owen, Jonathan S.,Parkin, Gerard
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p. 177 - 183
(2015/08/18)
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- Aryl(dimethyl)gallium compounds and methyl(diphenyl)gallium: Synthesis, structure, and redistribution reactions
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Treatment of diphenylmercury with an excess of trimethylgallium at higher temperatures resulted in the formation of dimethyl(phenyl)gallium (1). Similarly, reaction of 1-chloromercurio(4-methylbenzene) and 1-chloromercurio(4-tert-butylbenzene) with an excess of trimethylgallium gave dimethyl(4methylphenyl)gallium (2) and dimethyl(4-tert-butylphenyl)gallium (3), respectively. Treatment of diphenylmercury with an equivalent amount of trimethylgallium resulted in the formation of methyl(diphenyl)gallium (4). The X-ray crystallographic studies of compounds 1, 2, 3, and 4 revealed the presence of trigonal planar coordinate gallium atoms in monomeric molecules, which associate to polymeric strands by additional intermolecular gallium π-aryl contacts, thus leading to an overall trigonal bipyramidal coordination geometry at gallium. Compounds 1-4 are stable in the solid state and in solution. Substituent redistribution reactions take place at higher temperatures and at room temperature in the presence of THF. Compound 1 could also be prepared by the reaction of triphenylgallium with an excess of trimethylgallium at higher temperatures.
- Jutzi, Peter,Izundu, Joseph,Neumann, Beate,Mix, Andreas,Stammler, Hans-Georg
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p. 4565 - 4571
(2009/02/07)
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- Symmetrization of methylmercury (II) and phenylmercury (II) salts induced by the tripodal ligand N(CH2CH2PPh2)3
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Both ionic [HgR(DMSO)][CF3SO3] (R = Me or Ph) and covalent HgMel organomercury(II) compounds react with the tripodal ligand N(CH2CH2PPh2)3 (np3) to yield as ultimate products Hg(
- Cecconi, Franco,Ghilardi, Carlo A.,Midollini, Stefano,Orlandini, Annabella,Vacca, Alberto
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p. 153 - 156
(2007/10/03)
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- Electrophilic cleavages in (CH3)3SnCH2M(CH3)3 (M = Sn, Ge, Si, C). 1. Product distribution
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The extent to which Sn-CH2 and/or Sn-CH3 cleavage occurs in (CH3)3SnCH2M(CH3)3 (M = Sn, Ge, Si) in reactions with several electrophiles has been determined. With iodine and with
- Hawker, Darryl W.,Wells, Peter R.
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p. 821 - 825
(2008/10/08)
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- Selectivity and reactivity in reactions of methylaryltitanium(IV) complexes with electrophiles
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Methyl or phenyl for halogen-exchange reactions occur between [TiMe2(η-C5H5)2] or [TiPh2(η-C5H5)2] with [TiX2(η-C5H5)2], X = halogen, to give [TiXMe(η-C5H5)2] or [TiXPh(η-C5H5)2], respectively. The reactions are complicated by parallel decomposition of the methyl- or phenyltitanium complexes, which is catalyzed by [TiX2(η-C5H5)2] or [TiXR(η-C5H5)2]. In general, there is little difference in the rates of reaction of [TiMe2(η-C5H5)2] and [TiPh2(η-C5H5)2] toward the symmetrization reactions. These reagents also transfer a methyl group or phenyl group to platinum(II) or gold(III), but there are again side reactions. The complex [TiMePh(η-C5H5)2] reacts with electrophiles HCl, HOAc, HgCl2, and MeHgCl to give cleavage of both methyl- and phenyltitanium bonds with little selectivity. In cleavage of [TiMe(C6H4X)(η-C5H5) 2] there is a correlation of the selectivity for cleavage of the aryl group by electrophiles HCl or HgCl2 with the σ+ parameters of substituents X. A mechanism of reaction involving electron transfer from the complex to the electrophile followed by rapid cleavage is tentatively suggested.
- Puddephatt, Richard J.,Stalteri, Maria A.
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p. 1400 - 1405
(2008/10/08)
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