Thiolate Sulfur Atoms Research Articles

Synthesis, spectroscopic and structural characterization of diphenyltin(IV) complexes of acetone Schiff bases of S-alkyldithiocarbazates

New diphenyltin(IV) complexes of empirical formula, [Sn(C 6H 5) 2( NS)Cl] ( NS = anionic forms of the acetone Schiff bases of S-methyl or S-benzyldithiocarbazate) have been prepared and characterized by IR, NMR and Mössbauer spectroscopic techniques. The crystal and molecular structures of the acetone Schiff bases of S-methyldithiocarbazate (Hacsme) and S-benzyldithiocarbazate (Hacsbz) and their tin(IV) complexes have been determined by X-ray diffraction. In the solid state, both the Schiff bases exist in their thioketo tautomeric forms with the azomethine nitrogen atom trans to the thione sulfur atom but in the tin(IV) complexes they are present in their deprotonated ene-thiolate forms being coordinated to the tin atom as bidentate chelating agents via the azomethine nitrogen and thiolate sulfur atoms. The tin atom adopts a five-coordinate, approximately trigonal bipyramidal geometry, with the thiolate sulfur atom of the Schiff base and the two phenyl groups occupying the equatorial positions. The azomethine nitrogen atom and the chlorine ligand occupy axial positions. The distortion from a regular trigonal bipyramidal or a square-pyramidal geometry is attributed to the restricted bite sizes of the five-membered chelate rings.

Pt4S4 Clusters with Functionalized Thiosemicarbazones derived from 5‐Acetylbarbituric Acid

AbstractReaction of K2[PtCl4] with thiosemicarbazones derived from 5‐acetylbarbituric acid led to the isolation of the tetranuclear species [Pt(AcbM)]4 · 2/2DMSO · 2DMSO · 5H2O (1) and [Pt(AcbE)]4 · 4DMSO · 2H2O (2) (H2AcbM = 5‐acetylbarbituric‐4N‐methyl thiosemicarbazone and H2AcbE = 5‐acetylbarbituric‐4N‐ethyl thiosemicarbazone). Both of these compounds feature a Pt4S4 cluster in which some of the Pt–Pt distances suggest the existence of weak metal‐metal interactions. Crystals of these tetranuclear species are stabilized by intermolecular π‐π stacking interactions. The two compounds have almost equivalent molecular structures, differing only in the orientation of the substituent on the amine nitrogen atom of the thiosemicarbazone. The two tetranuclear complexes contain the thiosemicarbazone bonded as a terdentate ligand to the platinum atom through the thiolate sulfur atom, the azomethine nitrogen atom and the alcoholate oxygen atom of the 5‐acetylbarbiturate function.

Probing Lead(II) Bonding Environments in 4-Substituted Pyridine Adducts of (2,6-Me2C6H3S)2Pb: An X-ray Structural and Solid-State 207Pb NMR Study

The effect of subtle changes in the sigma-electron donor ability of 4-substituted pyridine ligands on the lead(II) coordination environment of (2,6-Me(2)C(6)H(3)S)(2)Pb (1) adducts has been examined. The reaction of 1 with a series of 4-substituted pyridines in toluene or dichloromethane results in the formation of 1:1 complexes [(2,6-Me(2)C(6)H(3)S)(2)Pb(pyCOH)](2) (3), [(2,6-Me(2)C(6)H(3)S)(2)Pb(pyOMe)](2) (4), and (2,6-Me(2)C(6)H(3)S)(2)Pb(pyNMe(2)) (5) (pyCOH = 4-pyridinecarboxaldehyde; pyOMe = 4-methoxypyridine; pyNMe2 = 4-dimethylaminopyridine), all of which have been structurally characterized by X-ray crystallography. The structures of 3 and 4 are dimeric and have psi-trigonal bipyramidal S(3)N bonding environments, with the 4-substituted pyridine nitrogen and bridging sulfur atoms in axial positions and two thiolate sulfur atoms in equatorial sites. Conversely, compound 5 is monomeric and exhibits a psi-trigonal pyramidal S(2)N bonding environment at lead(II). The observed structures may be rationalized in terms of a simple valence bond model and the sigma-electron donor ability of the 4-pyridine ligands as derived from the analysis of proton affinity values. Solid-state (207)Pb NMR experiments are applied in combination with density functional theory (DFT) calculations to provide further insight into the nature of bonding in 4, 5, and (2,6-Me(2)C(6)H(3)S)(2)Pb(py)(2) (2). The lead chemical shielding (CS) tensor parameters of 2, 4, and 5 reveal some of the largest chemical shielding anisotropies (CSA) observed in lead coordination complexes to date. DFT calculations using the Amsterdam Density Functional (ADF) program, which take into account relativistic effects using the zeroth-order regular approximation (ZORA), yield lead CS tensor components and orientations. Paramagnetic contributions to the lead CS tensor from individual pairs of occupied and virtual molecular orbitals (MOs) are examined to gain insight into the origin of the large CSA. The CS tensor is primarily influenced by mixing of the occupied MOs localized on the sulfur and lead atoms with virtual MOs largely comprised of lead 6p orbitals.

Synthesis, characterization, and crystal structure of cobalt(II) complex with 2-oximino-3-thiosemicarbazone-2,3-butanedione

The reaction of cobalt(II) chloride with the tridentate ligand 2-oximino-3-thiosemicarbazone-2,3-butanedione [Hotsb (1)] leads to the formation of the novel six-coordinated complex [Co(otsb)2]·2H2O (2). This complex has been synthesized and characterized by X-ray crystallography, spectroscopic and cyclic voltammetric measurements. The ligand Hotsb (1) obtained by the condensation of 2,3-butanedione monoxime and thiosemicarbazide is used for the preparation of complex 2. The Hotsb (1) crystallizes into a monoclinic lattice with space group P21/c. The crystal structure of 2 shows a distorted mer-octahedral geometry in which the ligands are coordinated as uninegatively charged tridentate chelating agents via the hydrazine nitrogen atoms, the azomethine nitrogen atoms, and the thiolate sulfur atoms. The cyclic voltammogram of 2 undergoes two irreversible one-electron waves corresponding to CoII/CoIII and CoII/CoI processes.

Synthesis and spectral characterization of zinc(II) complexes of N(4)-substituted thiosemicarbazone derived from salicylaldehyde: Structural study of a novel –OH free Zn(II) complex

Five novel zinc(II) complexes of salicylaldehyde 3-hexamethyleneiminyl thiosemicarbazone were synthesized and physico-chemically characterized. The complexes were given the formulae [Zn(HL) 2] ( 1), [Zn(L)py] ( 2), [Zn(L)bipy] · 3.5H 2O ( 3), [Zn(L)phen] · H 2O ( 4) and [Zn(L)γ-pic] ( 5). The thiosemicarbazone binds the metal as a dianionic ONS donor ligand in all the complexes, except in 1. Compound 1 is a homoleptic complex with zinc occupying the center of a distorted tetrahedral environment and being coordinated by two azomethine nitrogen and two thiolate sulfur atoms.

The Unexpected Desulfurization of 4-Aminothiophenols

Thermolysis of 4-aminophenyl benzyl sulfide at 523 K in the hydrogen donor solvent (HDS), 9,10-dihydroanthracene (AnH2), gave 4-aminothiophenol and toluene as the predominant products of the homolytic S-C bond cleavage. Under these conditions, a portion of the 4-aminothiophenol was desulfurized to aniline with first-order kinetics and with a rate constant estimated by kinetic modeling to be 7.0x10(-6) s-1. Starting with 4-NH2C6H4SH at 523 K, it was found that sulfur loss was more efficient in the non-HDSs, anthracene and hexadecane, than in AnH2. Under similar (competitive) reaction conditions, YC6H4SHs with Y=H, 4-CN, and 3-CF3 were completely inert; with Y=4-CH3O, there was some very minor desulfurization, whereas with Y=4-N(CH3)2 and 4-N(CH3)(H), the sulfur extrusions were as fast as that for Y=4-NH2. We tentatively suggest that this apparently novel reaction is a chain process initiated by the bimolecular formation of diatomic sulfur, S2, followed by a reversible addition of ground state, triplet 3S2 to the thiol sulfur atom, 4-NH2C6H4S upward arrow(SS upward arrow)H, and insertion into the S-H bond, 4-NH2C6H4SSSH. In a cascade of reactions, aniline and S8 are formed with the chains being terminated by reaction of 4-NH2C6H4S upward arrow(SS upward arrow)H with 4-NH2C6H4SH. Such a reaction mechanism is consistent with the first-order kinetics. That this reaction is primarily observed with 4-YC6H4SH having Y=N(CH3)2, N(CH3)(H), and NH2 is attributed to the fact that these compounds can exist as zwitterions.

Nickel Thiolate Complexes as Ligands for Copper and Zinc: Novel Additions to a Library of Binding Modes

AbstractThe reactivity of the two nickel complexes [Ni(xbsms)] and [Ni(bsms)2] [H2xbsms = α,α′‐bis(4‐mercapto‐3,3‐dimethyl‐2‐thiabutyl)‐o‐xylene; Hbsms = 4‐mercapto‐3,3‐dimethyl‐1‐phenyl‐2‐thiabutane] towards copper iodide and zinc bromide has been investigated. The reactions yield novel aggregates of higher nuclearity with topologies that are different from previous reports; the nickel complexes in all cases can be considered as didentate S ligands. The X‐ray structure of the novel octanuclear cluster [{Ni(bsms)2}3(CuI)5] shows a unique arrangement in which the cis‐NiS2S′2 units act as didentate ligands to a trigonal‐bipyramidal array of five CuI ions. The tetranuclear structure of [{Ni(xbsms)CuI}2] shows unprecedented asymmetric bridging of the thiolate sulfur atoms, with one of the thiolate groups binding to one copper ion and the other one μ3‐bridging to two copper ions. The complex is located on a crystallographic twofold axis and the complex in a single crystal is enantiomerically pure. The trinuclear complex [Ni2(bsms)3ZnBr3] is formed as a result of dissociation of the didentate bsms ligand from part of the mononuclear complex and reassembly to form a dinuclear core to which the ZnBr3– unit is coordinated to a single thiolate sulfur atom. A complex of stoichiometry [Ni3(xbsms)2(ZnBr3)2] has also been isolated and a structure proposal based on spectroscopic properties is given. All complexes have been characterised by analytical and spectroscopic methods. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Structural and spectral studies of novel Co(III) complexes of N(4)-substituted thiosemicarbazones derived from pyridine-2-carbaldehyde

Seven bis(ligand) Co(III) complexes { [ CoL 2 1 ] NO 3 · H 2 O ( 1 ) , [ CoL 2 1 ] Cl · 2 H 2 O ( 2 ) , [ CoL 2 1 ] ClO 4 ( 3 ) , [ CoL 2 2 ] NO 3 ( 4 ) , [ CoL 2 2 ] Cl · 2 H 2 O ( 5 ) , [ CoL 2 3 ] Br · 2 H 2 O ( 6 ) , [ CoL 2 3 ] ClO 4 · H 2 O ( 7 ) } of three thiosemicarbazone ligands {pyridine-2-carbaldehyde-N(4)- p-methoxyphenyl thiosemicarbazone [HL 1], pyridine-2-carbaldehyde-N(4)-2-phenylethyl thiosemicarbazone [HL 2] and pyridine-2-carbaldehyde-N(4)-(methyl),N(4)-(phenyl) thiosemicarbazone [HL 3]} were synthesized and physico-chemically characterized. All complexes are assigned octahedral geometries on the basis of spectral studies. The ligands deprotonate and coordinate by means of pyridine nitrogen, azomethine nitrogen, and thiolate sulfur atoms. The single crystal X-ray structures of HL 3 and two nitrate compounds are discussed. The structural studies corroborate the spectral characterization.

Symmetrisation in the Interaction of Chloro[2‐(dimethylaminomethyl)phenyl‐C1]mercury(II) with Thiosemicarbazone Derivatives of Pyridine‐2‐carboxamide and Pyrazin‐2‐carboxamide

AbstractPyridine‐ and pyrazine‐2‐carboxamide thiosemicarbazones (HAm4DH and HAmpz4DH) or their N4,N4‐dimethyl derivatives (HAm4DM and HAmpz4DM) react with chloro[2‐(dimethylaminomethyl)phenyl‐C1]mercury(II), [Hg(damp)Cl], to give the tetrahedral [Hg(TSC)2] complexes [TSC = Am4DH (1), Am4DM (2), Ampz4DH (3) or Ampz4DM (4)]. Spectroscopic studies and a X‐ray structural analysis show that the potentially tridentate thiosemicarbazones adopt S,N coordination modes, with each deprotonated thiosemicarbazone binding to the HgII centre through the azomethine nitrogen and the thiolate sulfur atoms, whereas the heterocyclic nitrogen atoms are free of coordination. Intra‐ and intermolecular hydrogen bonding in all complexes and specific C–H···π interactions with the chelate or pyridyl rings of the complexes 1 and 2 were found in the crystal structures. Furthermore, [Hg(damp)Cl] undergoes symmetrisation to give the symmetric unit [Hg(Hdamp)2]2+ in which the Hdamp is protonated at the nitrogen. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Synthesis, crystal structures, and two-photon absorption properties of dithiocarbazate Zn(II) and Pd(II) complexes

A new bidentate Schiff base ligand (abbreviated as L) derived from the condensation of S-methyldithiocarbazate (SMDTC) with 9-fluorenone, and its complexes ML 2 (M = Ni(II), Zn(II) and Pd(II)) have been synthesized and fully characterized by elemental analyses, IR, molar conductivity and UV–vis spectroscopy. The structures of complexes ZnL 2 and PdL 2 have been determined by X-ray diffraction analysis. Complex ZnL 2 adopts a distorted tetrahedral geometry with the azomethine nitrogen atom and the thiolate sulfur atom. The coordination geometry about the Pd(II) is surprisingly a cis-configuration square-planar formed by the Pd(II) atom coordinating to the NS bidentate ligand. Detailed crystal structure analyses show that the cis-positioning of the two ligands was stabilized by the π–π stacking interactions between the two delocalized diazafluorene moieties. The two-photon absorption of L and ML 2 solutions (in DMF) was measured at 532 nm by the open-aperture Z-scan technique.

Synthesis, characterization and X-ray crystallographic structural study of copper(II) and nickel(II) complexes of the 2-quinoline carboxaldehyde Schiff base of S-methyldithiocarbazate (Hqaldsme)

Complexes of general formulae, [Cu(qaldsme)(X)(CH 3OH) n ] and [Ni(qaldsme) 2] · 0.5CH 3CN (qaldsme = anionic form of the 2-quinoline carboxaldehyde Schiff base of S-methyldithiocarbazate; X = NCS −, I −, NO 3 - ; n = 0 or 1) have been synthesized and characterized by magnetic and spectroscopic techniques. X-ray crystal structure determination of [Cu(qaldsme)(ONO 2)(CH 3OH)] ( 1), [Cu(qaldsme)(NCS)] 2 ( 2) and [Ni(qaldsme) 2] · 0.5CH 3CN ( 4) shows that the nitrato-complex of copper ( 1) is monomeric and five-coordinate and the thiocyanato-complex ( 2) has a novel thiolate sulfur-bridged dimeric structure in which each of the copper(II) ions adopts a five-coordinate, approximately square-pyramidal geometry, with a CuN 3S 2 coordination kernel. The nickel(II) complex ( 3) has a distorted octahedral geometry with meridional dispositions of the two uninegatively charged tridentate NNS ligands. In all these complexes, the Schiff bases are coordinated in their iminothiolate forms via the quinoline nitrogen atom, the azomethine nitrogen atom and the thiolate sulfur atom.

Synthesis, characterization and bioactivity of mixed-ligand Cu(II) complexes containing Schiff bases derived from S-benzyldithiocarbazate and saccharinate ligand and the X-ray crystal structure of the copper-saccharinate complex containing S-benzyl-β- N-(acetylpyrid-2-yl)methylenedithiocarbazate

Mixed-ligand complexes of general formula, [Cu(NNS)(sac)] (NNS′ = S-benzyl-β- N-(2-acetylpyrid-2-yl)methylenedithiocarbazate, NNS″ = S-benzyl-β- N-(2-benzoylpyrid-2-yl)methylenedithiocarbazate and NNS‴ = S-benzyl-β- N-(6-methylpyrid-2-yl)methylenedithio-carbazate, sac = the saccharinate anion) have been synthesized by reacting [Cu(sac) 2(H 2O) 4] · 2H 2O with the appropriate ligands in ethanol and characterized by various physico-chemical techniques. Magnetic and spectral evidence indicate that the complexes are four-coordinate in which the Schiff bases coordinate as NNS ligands and the sac- anion coordinates as a unidentate N-donor ligand. An X-ray crystallographic structural analysis of [Cu(NNS′)(sac)] shows that the complex has a distorted square-planar geometry with the Schiff base coordinated to the copper (II) ion as a uninegatively charged tridentate chelating agent via the pyridine nitrogen atom, the azomethine nitrogen atom and the thiolate sulphur atom while the fourth coordination position is occupied by the N-bonded saccharinate anion. The complexes have been evaluated for their biological activities against selected pathogens and cancer cell lines. They display weak activity against the pathogenic bacteria and fungi. The complexes were highly active against the leukemic cell line (HL-60) but only [Cu(NNS′)(sac)] was found to exhibit strong cytotoxicity against the ovarian cancer cell line (Caov-3). All complexes were inactive against the breast cancer cell line (MCF-7).

Thiolate exchange in [Tm R]ZnSR′ complexes and relevance to the mechanisms of thiolate alkylation reactions involving zinc enzymes and proteins

The zinc and cadmium thiolate complexes [ Tm Bu t ] MSCH 2 C ( O ) N ( H ) Ph (M = Zn, Cd) may be obtained via treatment of the respective methyl complex [ Tm Bu t ] MMe with PhN(H)C(O)CH 2SH. The molecular structure of [ Tm Bu t ] ZnSCH 2 C ( O ) N ( H ) Ph has been determined by X-ray diffraction, thereby demonstrating the presence of an intramolecular N–H ⋯ S hydrogen bond between the amide N–H group and thiolate sulfur atom. [ Tm Bu t ] ZnSCH 2 C ( O ) N ( H ) Ph mimics the function of the Ada DNA repair protein by undergoing alkylation with MeI to give [ Tm Bu t ] ZnI and MeSCH 2C(O)N(H)Ph. A series of crossover experiments and 1H NMR magnetization transfer studies establish that thiolate exchange between [Tm R]ZnSR′ derivatives is facile in this system, an observation that supports the previous suggestion that the alkylation of [Tm Ph]ZnSCH 2C(O)N(H)Ph by MeI may proceed via a sequence that involves dissociation of [PhN(H)C(O)CH 2S] −.

The Preparation, Characterization and Biological Activity of Palladium(II) and Platinum(II) Complexes of Tridentate NNS Ligands Derived from S-methyl- and S-benzyldithiocarbazates and the X-ray Crystal Structure of the [Pd(mpasme)Cl] Complex

New complexes of general formula, [M(NNS)Cl] (M = PdII, PtII; NNS = anionic forms of the 6-methyl-2-formylpyridine Schiff bases of S-methyl- and S-benzyldithiocarbazates) have been prepared and characterized by a variety of physico-chemical techniques. Based on conductance and spectral evidence, a square-planar structure is assigned to these complexes. The crystal and molecular structure of the [Pd(mpasme)Cl] complex (mpasme=anionic form of the 6-methyl-2-formylpyridine Schiff base of S-methyldithiocarbazate) has been determined by X-ray diffraction. The complex has a distorted square-planar geometry with the ligand coordinated to the palladium(II) ion via the pyridine nitrogen atom, the azomethine nitrogen atom and the thiolate sulfur atom; the fourth coordination position around the palladium(II) ion is occupied by the chloride ligand. The distortion from a regular square-planar geometry is ascribed to the restricted bite angle of the ligand. Both the Schiff bases exhibit strong cytotoxicity against the human ovarian cancer (Caov-3) cell lines, the S-methyl derivative being two times more active than the S-benzyl derivative. The [Pt(mpasme)Cl] complex is moderately active but the palladium(II) complex is weakly active against this cancer. None of the complexes of Hmpsbz are active against Caov-3. The Schiff base, Hmpasme exhibits moderate activity against the bacteria, MRSA, P. aeruginosa and S. typhimurium but is inactive against B. subtilis. Coordination of the ligand with palladium(II) substantially reduces its activity. The Schiff base, Hmpasbz and its palladium(II) and platinum(II) complexes are inactive against these bacteria. The Schiff bases and their palladium(II) and platinum (II) complexes are inactive against the pathogenic fungi, C. albican, Aspergillus ochraceous and Saccharomyces cerevisiae.

Novel Rhenium Chelate System Derived from Dimercaptosuccinic Acid for the Selective Labeling of Biomolecules

This work is part of an effort to develop chelating agents for stable binding and easy conjugation of Re-188 to biologically interesting structures. Starting from the well-known in vivo stability of [(188)ReO(DMSA)(2)](-), we want to exploit this coordination system for the design of (188)ReO(V) chelates, which are stable toward reoxidation to perrhenate and toward ligand exchange under all conditions of radiopharmaceutical development. Therefore, a new type of tetradentate ligand has been synthesized by bridging two molecules of N,N'-diisobutyl-2,3-dimercaptosuccinamide with N-(3-aminopropyl)propane-1,3-diamine. The resulting stereoisomeric tetrathiolato S(4) ligand of composition ((i)()Bu)(2)N(O)C-C(SH)-C(SH)-C(O)NH-(CH(2))(3)-NH-(CH(2))(3)-NHC(O)-C(SH)-C(SH)-C(O)N((i)Bu)(2) forms anionic five-coordinate oxorhenium(V) complexes by a ligand-exchange reaction of NBu(4)[ReOCl(4)] in methanol. In the absence of a base, the compounds were isolated as "betaine", [ReO(S(4))], with the protonated nitrogen of the bridge serving as an internal "counterion". Two representatives have been fully characterized in both the solid and solution states and found to adopt the expected square-pyramidal coordination geometry. The equatorial plane is formed by four thiolate sulfur atoms, whereas the oxygen occupies the apical position. The orientation of the metal oxo group is exo in relation to the carbamido groups in both isomers. Both complexes are stereoisomeric regarding the junction of the triamine chain.

Significance of Intermolecular S···C(π) Interaction Involving M–S and –C=O Centers in Crystal Structures of Metal Thiolate Complexes

AbstractThe database analysis of intermolecular S···C(π) distances involving a metal‐bonded thiolate sulfur atom and various C(π)‐centered Lewis acid domains provided evidences for M–S···C(π) contacts as resulting from specific noncovalent interactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Intramolecular NH···S Hydrogen Bonding in the Zinc Thiolate Complex [TmPh]ZnSCH2C(O)NHPh: A Mechanistic Investigation of Thiolate Alkylation as Probed by Kinetics Studies and by Kinetic Isotope Effects

The zinc thiolate complex [Tm(Ph)]ZnSCH2C(O)N(H)Ph, which features a tetrahedral [ZnS4] motif analogous to that of the Ada DNA repair protein, may be obtained by the reaction of Zn(NO3)2 with [Tm(Ph)]Li and Li[SCH2C(O)N(H)Ph] ([Tm(Ph)] = tris(2-mercapto-1-phenylimidazolyl)hydroborato ligand). Structural characterization of [Tm(Ph)]ZnSCH2C(O)N(H)Ph by X-ray diffraction demonstrates that the molecule exhibits an intramolecular N-H...S hydrogen bond between the amide N-H group and thiolate sulfur atom, a structure that is reproduced by density functional theory (DFT) calculations. The thiolate ligand of [Tm(Ph)]ZnSCH2C(O)N(H)Ph is subject to alkylation, a reaction that is analogous to the function of the Ada DNA repair protein. Specifically, [Tm(Ph)]ZnSCH2C(O)N(H)Ph reacts with MeI to yield PhN(H)C(O)CH2SMe and [Tm(Ph)]ZnI, a reaction which is characterized by second-order kinetics that is consistent with either (i) an associative mechanism or (ii) a stepwise dissociative mechanism in which the alkylation step is rate determining. Although the kinetics studies are incapable of distinguishing between these possibilities, a small normal kinetic isotope effect of kH/kD = 1.16(1) at 0 degrees C for the reaction of [Tm(Ph)]ZnSCH2C(O)N(H*)Ph (H* = H, D) with MeI is suggestive of a dissociative mechanism on the basis of DFT calculations. In particular, DFT calculations demonstrate that a normal kinetic isotope effect requires thiolate dissociation because it results in the formation of [PhN(H)C(O)CH2S]- which, as an anion, exhibits a stronger N-H...S hydrogen bonding interaction than that in [Tm(Ph)]ZnSCH2C(O)N(H)Ph. Correspondingly, mechanisms that involve direct alkylation of coordinated thiolate are predicted to be characterized by kH/kD < or = 1 because the reaction involves a reduction of the negative charge on sulfur and hence a weakening of the N-H...S hydrogen bonding interaction.

Unprecedented Coordination Mode Variation of Group 13 Metal–Alkyl Compounds Derived from Methyl Thiosalicylate

AbstractThe X‐ray structure analysis of the alkylaluminum and‐indium compounds derived from methyl thiosalicylate,Me2Al(SC6H4‐2‐CO2Me) and [Me2In(μ‐SC6H4‐2‐CO2Me)]2, revealed that the intermolecular S···C(π) interaction between the Al–S thiolate units and the ester π‐surface can effectively compete with the hypercoordinate sulfur–metal dative bond. The former compound exists as the noncovalently bonded dimer involving the thiolate sulfur atom and the electrophilic carbon atom of the ester functionality, whereas the indium complex is a five‐coordinate dimer with the In2(μ‐S)2 central core. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2005)

Mercury Binding Sites in Thiol-Functionalized Mesostructured Silica

Thiol-functionalized mesostructured silica with anhydrous compositions of (SiO(2))(1)(-)(x)()(LSiO(1.5))(x)(), where L is a mercaptopropyl group and x is the fraction of functionalized framework silicon centers, are effective trapping agents for the removal of mercuric(II) ions from water. In the present work, we investigate the mercury-binding mechanism for representative thiol-functionalized mesostructures by atomic pair distribution function (PDF) analysis of synchrotron X-ray powder diffraction data and by Raman spectroscopy. The mesostructures with wormhole framework structures and compositions corresponding to x = 0.30 and 0.50 were prepared by direct assembly methods in the presence of a structure-directing amine porogen. PDF analyses of five mercury-loaded compositions with Hg/S ratios of 0.50-1.30 provided evidence for the bridging of thiolate sulfur atoms to two metal ion centers and the formation of chain structures on the pore surfaces. We find no evidence for Hg-O bonds and can rule out oxygen coordination of the mercury at greater than the 10% level. The relative intensities of the PDF peaks corresponding to Hg-S and Hg-Hg atomic pairs indicate that the mercury centers cluster on the functionalized surfaces by virtue of thiolate bridging, regardless of the overall mercury loading. However, the Raman results indicate that the complexation of mercury centers by thiolate depends on the mercury loading. At low mercury loadings (Hg/S < or = 0.5), the dominant species is an electrically neutral complex in which mercury most likely is tetrahedrally coordinated to bridging thiolate ligands, as in Hg(SBu(t))(2). At higher loadings (Hg/S 1.0-1.3), mercury complex cations predominate, as evidenced by the presence of charge-balancing anions (nitrate) on the surface. This cationic form of bound mercury is assigned a linear coordination to two bridging thiolate ligands.

Kupferkomplexe des neuen Chelatliganden 1‐Methyl‐2‐(2‐thiophenolato)‐1H‐benzimidazol (mtpb) und dessen Oxidationsprodukten

AbstractCopper Complexes of the New Chelate Ligand 1‐Methyl‐2‐(2‐thiophenolato)‐1H‐benzimidazole (mtpb) and of its Oxidation ProductsAnodic electrolysis of copper in acetonitrile in the presence of Hmtpb leads to formation of yellow [Cu4(mtbp)4] which was crystallized as a dichloromethane solvate with two crystallographically independent cluster molecules in the unit cell. The copper(I) atoms exhibit slightly pyramidal S2N coordination with bridging thiolate sulfur atoms. The two clusters contain the four copper atoms arranged in a more (Cu1‐Cu4) or less (Cu5‐Cu8) distorted bisphenoidal arrangement. Reaction of mtpb— with Cu(ClO4)2 under anoxic conditions also produces [Cu4(mtpb)4]. However, the admittance of O2 in the reaction of mtpb— with copper(II) acetate in methanol causes oxidation of the sulfur atoms; a square‐pyramidal configurated copper(II) complex [Cu(CH3CO2‐κ2O)(L1‐κN)(L2‐κN, O)] has been isolated and crystallographically characterized in which L1 is the neutral sulfinic methyl ester and L2— is the sulfonate derived from mtpb—.