Disulfide Ligands Research Articles

Organometallic-like C-H bond activation and C-S bond formation on the disulfide bridge in the RuSSRu core complexes.

C-S bond formations on the disulfide bridge in the dinuclear Ru(III) complexes have been found in the reaction with unsaturated organic molecules, such as alkenes and ketones. The reactions are initiated by the organometallic-like C-H bond activation. Through the mechanistic study of these novel reactions, the specific nature of the disulfide bridging ligand has been unveiled: (i) the double bond character of the sulfur-sulfur bond, which allows the Diels-Alder-type [4 + 2] cycloaddition reaction with butadiene to form a C(4)S(2) ring, (ii) the C-H bond activation on the S-S bond forming a C-S bond. All of the C-H activation reactions and the ensuing C-S bond formation reactions suggest that the disulfide ligand can act in a manner similar to the transition metal centers of the organometallic complexes.

Bridge coordination of bidentate ligands to a dinuclear η 6-arene-ruthenium(II) unit constructed by a chelating and bridging alkoxo ligand

Dinuclear η 6-areneruthenium(II) complex of the formula [Ru 2{η 6:η 1:μ-C 6H 5(CH 2) 3O} 2(μ-Cl)] + ( 2) was prepared by treatment of Ru{η 6-C 6H 5(CH 2) 3OH}Cl 2 with base. X-Ray structure analysis revealed 2 to contain two Ru centers bridged by Cl ligand as well as by two alkoxo groups, which are tethered to η 6-arene ligands. Treatment of 2 with Ag + in acetonitrile afforded dicationic complex [Ru 2{η 6:η 1:μ-C 6H 5(CH 2) 3O} 2(CH 3CN) 2] 2+ ( 3) in which two CH 3CN ligands are located trans to each other with respect to the Ru 2O 2 plane. Irradiation with UV light (300–400 nm) of a CH 3CN solution of 3 and trans-azobenzene gave cis-azobenzene complex [Ru 2{η 6:η 1:μ-C 6H 5(CH 2) 3O} 2(μ- cis-PhNNPh)] 2+ ( 4). Cis-azobenzene ligand of 4 dissociated under irradiation of light (>510 nm) to give 3 in CH 3CN or disulfide complex [Ru 2{η 6:η 1:μ-C 6H 5(CH 2) 3O} 2(μ-PhSSPh)] 2+ ( 6) in the presence of the disulfide. X-ray structure determination of 4 and 6 established bridge coordination of cis-azobenzene and disulfide ligands. Reaction of 3 with pyridazine afforded similar dimeric complex [Ru 2{η 6:η 1:μ-C 6H 5(CH 2) 3O} 2(μ-pyridazine)] 2+ ( 7), while the reaction with bipyridine afforded monomeric alkoxo chelate complex [Ru{η 6:η 1-C 6H 5(CH 2) 3O}(bipy)] + ( 8).

Basic Reaction Steps in the Sulfidation of Crystalline Tungsten Oxides

The sulfidation of crystalline m-WO3 and WO3·H2O and the thermal decomposition of (NH4)2WO2S2 to an {WOS2} oxysulfide and (NH4)2WS4 to {WS3} were studied by means of temperature-programmed sulfidation (TPS), X-ray photoelectron spectroscopy (XPS), thermogravimetrical analysis (TGA), and laser Raman spectroscopy. Several basic steps of the sulfidation reaction could be resolved and explained in terms of the structures of crystalline m-WO3 and WO3·H2O. The sulfidation reaction starts at low temperatures with a reduction of the crystalline oxides by reaction with H2S without incorporation of sulfur. Only after this reduction does an exchange of terminal O2- ligands of the oxides for S2- take place. In subsequent W−S redox reactions S22- ligands form, which leads to oxysulfidic intermediates. The {WOS2} oxysulfide phase serves as a reference of structural features of oxysulfides. The presence of oxygen at bridging and terminal positions as well as of disulfide ligands seems to be a common structural property ...

Fourier transform Raman spectroscopic study of pressure‐induced ligand bond activation in a molybdenum–sulfur cluster

AbstractFourier transform Raman spectra of the prototype, triangular, transition metal–sulfur cluster anion [Mo3(S2)6S]2− were recorded at pressures up to 60 kbar with the aid of a diamond‐anvil cell (DAC). The pressure dependences (∂ν/∂p) of the Raman bands indicate a structural change at around 10–15 kbar. The SS stretching mode for the bridging disulfide ligands exhibits a slightly negative ∂ν/∂p value (−0.08), suggesting that SS bonds are weakened, i.e. activated, at high pressures. This pressure‐induced activity parallels the observed nucleophilic substitution reactivity of the S2 groups in this molybdenum cluster anion. In view of this, a preliminary investigation of the reaction between [Mo3(S2)6S]2− and CN− was undertaken in the solid state in the DAC under high pressure. Copyright © 2002 John Wiley & Sons, Ltd.

ChemInform Abstract: New C2‐Symmetric Chiral Disulfide Ligands Derived from (R)‐Cysteine.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Niobium persulfide complexes: synthesis and structural characterization of [Et 4N][NbO(S 2) 2(bpy)]·DMF, [PPN][NbO(CS 3)(S 2)(bpy)] and [Et 4N][NbO(S 2C 2(CO 2Me) 2)(S 2)(bpy)]·DMF complexes

The novel monomeric niobium persulfide complex, [Et 4N][NbO(S 2) 2(bpy)]·DMF ( I) was synthesized by the reaction of NbO(SPh) 4 − with elemental sulfur in the presence of 2,2′-dipyridyl in DMF. The reaction of I with carbon disulfide (CS 2) and dimethylacetylene dicarboxylate (DMA) affords [PNP][NbO(CS 3)(S 2)(bpy)] ( II) and [Et 4N][NbO(S 2C 2(CO 2Me) 2)(S 2)(bpy)]·DMF ( III) complexes, respectively. In this reaction, insertion reactions of the electrophile occurred at only one site of two equivalent disulfide ligands. In each complex, the Nb atom is seven coordinated and the anion has a distorted pentagonal bipyramidal geometry.

New C2-symmetric chiral disulfide ligands derived from (R)-cysteine

Several sulfur-containing optically active C2-symmetrical ligands have been synthesized from (R)-cysteine and applied successfully as chiral catalysts in the asymmetric addition of diethylzinc to aldehydes. The resulting secondary alcohols could be obtained in good yields and excellent enantiomeric excess.

Redox-Associated η1 to η2 Conversion of Disulfide Ligands in Dinuclear Ruthenium Complexes

Disulfide-bridged dinuclear ruthenium complexes [[Ru(MeCN)(P(OMe)(3))(2)](2)(mu-X)(mu,eta(2)-S(2))][ZnX(3)(MeCN)] (X = Cl (2), Br (4)), [[Ru(MeCN)(P(OMe)(3))(2)](2)(mu-Cl)(2)(mu,eta(1)-S(2))](CF(3)SO(3)) (5), [[Ru(MeCN)(P(OMe)(3))(2)](2)(mu-Cl)(mu,eta(2)-S(2))](BF(4)) (6), and [[Ru(MeCN)(2)(P(OMe)(3))(2)](2)(mu-Cl)(mu,eta(1)-S(2))](CF(3)SO(3))(3) (7) were synthesized, and the crystal structures of 2 and 4 were determined. Crystal data: 2, triclinic, P1, a = 15.921(4) A, b = 17.484(4) A, c = 8.774(2) A, alpha = 103.14(2) degrees, beta = 102.30(2) degrees, gamma = 109.68(2) degrees, V = 2124(1) A(3), Z = 2, R (R(w)) = 0.055 (0.074); 4, triclinic, P1 a = 15.943(4) A, b = 17.703(4) A, c = 8.883(1) A, alpha = 102.96(2) degrees, beta = 102.02(2) degrees, gamma = 109.10(2) degrees, V = 2198.4(9) A(3), Z = 2, R (R(w)) = 0.048 (0.067). Complexes 2 and 4 were obtained by reduction of the disulfide-bridged ruthenium complexes [[RuX(P(OMe)(3))(2)](2)(mu-X)(2)(mu,eta(1)-S(2))] (X = Cl (1), Br (3)) with zinc, respectively. Complex 5 was synthesized by oxidation of 2 with AgCF(3)SO(3). Through these redox steps, the coordination mode of the disulfide ligand was converted from mu,eta(1) in 1 and 3 to mu,eta(2) in 2 and 4 and further reverted to mu,eta(1) in 5. Electrochemical studies of 6 indicated that similar conversion of the coordination mode occurs also in electrochemical redox reactions.

Controlled Formation of Smaller Gold Nanoparticles by the Use of Four-Chained Disulfide Stabilizer

Size control of gold nanoparticles by tuning molecular cross section of stabilizer molecules is reported. A newly synthesized four-chained disulfide ligand was used as the stabilizer of gold nanoparticles, and the nanoparticles were prepared by NaBH4 reduction of gold ions. By the use of this stabilizer, smaller and monodispersed gold nanoparticles were obtained, when compared to those prapred by using conventional monoalkanethiols. The present design of stabilizer molecules can be used to systematically control the size of nanoparticles with atomic precision.

The N−H···S Hydrogen Bond in (TACN)2Fe2S6 (TACN = Triazacyclononane) and in Model Systems Involving the Persulfido Moiety: An ab Initio and DFT Study

Extended Huckel, DFT, and ab initio MP2 calculations have been carried out to rationalize the unprecedented structural characteristics of the recently synthesized complex (μ−η1-S2)3 (Fe-TACN)2 (TACN = triazacyclononane). The orbital interaction diagram between the metal−macrocycle dimer and the three disulfide ligands accounts for some of the observed properties of the complex: diamagnetism, existence of an Fe−Fe single bond, nucleophilicity of the terminal sulfur atoms. The unprecedented occurrence of a M2S6 core, as the very unusual μ−η1 coordination of the S2 ligands, however, requires further analysis. It was assumed that the key to the structural singularities of this complex should be sought in the network of intramolecular H···S bonds revealed by the crystallographic analysis and involving all six NH groups and all three terminal S atoms. We therefore report the first quantitative theoretical investigation of the energetics of intramolecular H···S bonds. Geometry optimizations have been carried ou...

Diels-Alder Type Addition of 1,3-Dienes to a Disulfide Bridging Ligand in Diruthenium Complexes Support of this work through a CREST grant of the Japan Science and Technology Corporation is gratefully acknowledged.

The dienophilic disulfide ligands that bridge the two Ru centers in the ruthenium dinuclear complexes react with conjugated dienes through a Diels–Alder cycloaddition to give new species which carry the C4S2 six-membered ring (see scheme).

Reactions of Thiiranes and a Thietane with a High Valent Metal Chloride

Ethylene sulfide and propylene sulfide react with the high valent metal complex Cp‘ReCl4 (Cp‘ = EtMe4C5) in THF solution to form a product with a chloroalkyl disulfide ligand of the formula Cp‘Re(Cl)3−S−S−CH(R)CH2Cl (R = H or Me). In contrast, the thietane S(CH2)3 reacts with Cp‘ReCl4 to form a simple adduct, and no ring-opening reaction has been identified.

Copper(II) and nickel(II) complexes of binucleating macrocyclic bis(disulfide)tetramine ligands.

Novel macrocyclic bis(disulfide)tetramine ligands and several Cu(II) and Ni(II) complexes of them with additional ligands have been synthesized by the oxidative coupling of linear tetradentate N2S2 tetramines with iodine. Facile demetalation of the Ni(II) oxidation products affords the free 20-membered macrocycles meso-9 and rac-9 and the 22-membered macrocycle 16, all of which are potentially octadentate N4S4 ligands. X-ray structure analyses reveal distinctly different conformations for the two isomers of 9; meso-9 shows a stepped conformation in profile with the disulfide groups corresponding to the rise of the step, whereas rac-9 exhibits a V conformation with the disulfide groups near the vertex of the V. No metal complexes of rac-9 have been isolated. Crystallographic studies of three Cu(II) complexes reveal that depending upon the size of the macrocyclic ligand and the nature of the additional ligands (I-, NCO-, and CH3CN), the Cu(II) coordination geometry shows considerable variation (plasticity), with substantial changes in the Cu(II)-disulfide bonding. Thus, a diiodide salt contains six-coordinate Cu(II) to which all four bridging disulfide sulfur atoms form strong equatorial bonds. In contrast, isocyanato complexes of the 20- and 22-membered macrocycles exhibit trigonal-bipyramidal Cu(II) and distorted cis-octahedral Cu(II) geometries, respectively, having only one and no short equatorially bound sulfur atoms. The coordination geometry of the latter complex can also be described as four-coordinate seesaw with two semicoordinated S(disulfide) ligands. Disulfide-->Cu(II) ligand-to-metal charge transfer absorptions of both isocyanato-containing Cu(II) species appear too weak to observe, probably because of poor overlap of the sulfur orbitals with the Cu(II) d-vacancy. The dual disulfide-bridged Ni(II) units of the crystallographically characterized octahedral Ni(II) complex of meso-9 with axial iodide and acetonitrile ligands promote substantial antiferromagnetic coupling (J = -13.0(2) cm-1).

Characterization of novel redox-active triruthenium(III) complexes with a disulfide alkyl ligand. Anion-dependent redox behaviour of monolayer assemblies on gold †

New oxo-centred acetate-bridged triruthenium(III) complexes with a long alkyl-chain disulfide ligand, (NC5H4)CH2NHC(O)(CH2)nSS(CH2)nC(O)NHCH2(C5H4N) (C5H4N represents a 4-pyridyl residue, n = 10; abbreviated as C10PY), have been prepared as a redox-active metal cluster adsorbate on gold electrodes: [Ru3(O)(CH3CO2)6(mpy)2(C10PY)]ClO45a (mpy = 4-methylpyridine), [Ru3(O)(CH3CO2)6(mpy)2(C10PY)]CF3SO35b. The preparation, spectroscopic and electrochemical properties of 5a,5b are presented and are compared with those of triruthenium(III) analogues of a shorter alkyl-chain disulfide ligand (n = 2; abbreviated as C2PY), e.g. [Ru3(O)(CH3CO2)6(mpy)2(C2PY)]ClO43a and [Ru3(O)(CH3CO2)6(MeIm)2(C2PY)]ClO44a (MeIm = 1-methylimidazole). Characterization of all the compounds was accomplished using 1H and 1H–1H COSY NMR, UV-vis and infrared spectroscopy, elemental analysis, fast-atom bombardment (FAB) mass spectrometry and cyclic voltammetry. Compounds 3a, 4a and 5a,5b in 0.1 M [n-Bu4N]PF6–CH3CN exhibit three {Ru3(O)} cluster core-based one-electron redox waves which are all reversible in the applied potential range between +1.2 and –2.0 V vs. Ag–AgCl. The redox potentials are dependent on the basicity of the terminal ligands (mpy and MeIm), but are insensitive to the length of the methylene chains of the disulfide ligand (C10PY and C2PY). Self-assembly of 5b on a gold electrode results in the formation of electrochemically stable monolayers which exhibit one-electron redox wave corresponding to the Ru3 redox process III,III,III–II,III,III in aqueous media containing 0.1 M supporting electrolytes. The redox potentials and the shape of the voltammetric waves of the surface-attached triruthenium complexes are found to be largely dependent upon the nature of anions used (ClO4−, CF3SO3−, NO3−, PF6− and SO42−) and also upon the basicity of terminal ligands on the {Ru3(O)} cluster moiety.

Polyferredoxin-based electrode materials.

Electrochemical oxidation of the hydrosulfide cluster [Fe4S4(SH)4]2- on gold, platinum or vitreous carbon in a methyl cyanide electrolyte leads to the growth of a conducting film. Spectroscopic and other evidence suggests that the film has cubane centres, predominately in the [4Fe4S]3+ oxidation state, which are linked by disulfide ligands to give an anionic array of [Fe4S4(S approximately)4]n- units. X-ray data suggests some long-range order in the electrode material. The polyferredoxin binds redox active cations consistent with an anionic array.

Remarkable S,N,S ′ tridentate chelation to palladium(II) by the monoanion derived from [Ph2P(S)NH]2CO

The reaction between [PdCl2(PhCN)2] and [Ph2P(S)NH]2CO (H2L) proceeds with monodeprotonation of an amine group in the disulfide ligand to give [Pd(HL)Cl] 1, in which the (HL)− anion supplies an S,N,S′ donor set to palladium(II), leading to disparate S,N chelate ring sizes at the metal.

Redox Chemistry of (1,4,7-Tris(4-tert-butyl-2-mercaptobenzyl)-1,4,7- triazacyclononane)ruthenium(III), [Ru(III)L]: Synthesis and Characterization of [Ru(II)(2)(L-L)](BPh(4))(4).10CH(3)CN and [LRuRuRuL](PF(6))(2).H(2)O.

The mononuclear blue complex [Ru(III)L] (1) where L represents the trianion of 1,4,7-tris(4-tert-butyl-2-mercaptobenzyl)-1,4,7-triazacyclononane has been synthesized by the reaction of H(3)L.3HPF(6) with [Ru(II)Cl(2)(dmso)(4)] in refluxing CH(3)OH in the presence of air. Chemical or electrochemical oxidation of 1 generates [Ru(II)(2)(L-L)](PF(6))(4) (2), a dinuclear species containing two Ru(II) ions and a neutral tris(disulfide) ligand L-L. The reaction of 1 with 1 equiv of [Ru(II)Cl(2)(dmso)(4)] produces the trinuclear species [LRuRuRuL](PF(6))(2) (3) in low yield. Complexes 2 and 3 have been structurally characterized by X-ray crystallography: [Ru(II)(2)(L-L)](BPh(4))(4).10CH(3)CN, C(194)H(218)B(4)N(16)Ru(2)S(6), crystallizes in the monoclinic space group C2/c with a = 28.734(5) Å, b = 16.347(3) Å, c = 37.986(7) Å, beta = 102.35(2) degrees, and Z = 4 whereas [LRuRuRuL](PF(6))(2).H(2)O, C(78)H(110)F(12)N(6)OP(2)Ru(3)S(6), crystallizes in the monoclinic space group P2(1)/n with a = 18.755(4) Å, b = 22.278(4) Å, c = 21.920(4) Å, beta = 91.69(3) Å, and Z = 4. The electro- and spectroelectrochemistry of 1-3 have been studied in detail as have their electronic structures by (1)H NMR, EPR, UV-vis, IR, and Raman spectroscopy.

Synthesis and electrochemical characterization of self-assembled monolayers of redox-active oxide-bridged triruthenium(III) clusters on Au(111)

Novel self-assembled monolayers of oxide and acetate-bridged triruthenium(III) complexes have been prepared on Au(111) electrode surface. Parent discrete triruthenium(III) complexes with a terminal disulfide ligand, [Ru3(μ3-O)(μ-CH3CO2)6(L)2(C2PY)]ClO4, where C2PY={NC5H4CH2NHC(O)(CH2)2S–}2, L=4-methylpyridine (mpy, 4a) and 1-methylimidazole (MeIm, 4b), were isolated through multistep synthesis. Complex 4a exhibits three reversible redox waves, while complex 4b exhibits two reversible and one irreversible redox waves in (n-C4H9)4NPF6/CH3CN, all ascribed to one-electron redox of the triruthenium cluster core. In aqueous solution containing a 0.1 M supporting electrolyte (NaClO4 or Na2SO4), self-assembled monolayers of 4a and 4b on Au(111) electrodes (4a/Au and 4b/Au) exhibit a single reversible redox wave, ascribed to the Ru3(III,III,III/II,III,III) redox process for the surface-attached clusters. The redox potential and the shape of the cyclic voltammograms of Ru3 cluster modified SAMs were affected by the kind of terminal ligands and supporting electrolytes.

Ligand and Tetrathiometalate Effects in Induced Internal Electron Transfer Reactions.

New rhenium sulfide complexes, [Re(IV)(2)(&mgr;-S)(2)(&mgr;-S(2))(&mgr;-S(2)COR)(S(2)COR)(2)](-) and [Re(IV)(2)(&mgr;-S)(2)(S(2)COR)(4)], and a new tungsten sulfide complex, [WS(S(2))(S(2)CC(6)H(5))(2)], have been synthesized and isolated via induced internal redox reactions involving the appropriate tetrathiometalate and 1,1-dithiolate disulfide. The red complex [Re(IV)(2)(&mgr;-S)(2)(&mgr;-S(2))(&mgr;-S(2)COR)(S(2)COR)(2)](-), 1, was isolated from the reaction of dialkylxanthogen disulfide, [(ROCS(2))(2)], and tetraethylammonium tetrathioperrhenate, [Et(4)N][Re(VII)S(4)]. Crystal structure analysis of 1 reveals an edge-sharing (&mgr;-S)(2) bioctahedron containing both bridging disulfide and xanthate ligands. This reaction is compared to the known reaction between tetraalkylthiuram disulfide, [(R(2)NCS(2))(2)], and [Et(4)N][ReS(4)], which produces the green complex [Re(IV)(2)(&mgr;-S)(2)(S(2)CNR(2))(4)]. The corresponding green alkyl xanthate analogue, [Re(IV)(2)(&mgr;-S)(2)(S(2)COR)(4)], 2, was synthesized by a simple redox reaction between rhenium pentachloride, ReCl(5), and potassium alkyl xanthate, [K(S(2)COR)]. Comparing 1 with other known [ReS(4)](-)/1,1-dithiolate disulfide reaction products, such as [Re(IV)(2)(&mgr;-S)(2)(S(2)CNR(2))(4)] and [Re(III)(S(2)CC(6)H(5))(S(3)CC(6)H(5))(2)], shows a correlation between the electron-donating ability of the ligand and the nature of the reaction product. Reactions of [Et(4)N](2)[Mo(VI)S(4)], [Et(4)N][Re(VII)S(4)], or [Et(4)N](2)[W(VI)S(4)] with dithiobenzoate disulfide, [(S(2)CC(6)H(5))(2)], reveal a correlation between the ligand-to-metal charge transfer energy band (LMCT(1)) of the tetrathiometalate and the reaction product. The known purple complex [Mo(IV)(S(2)CC(6)H(5))(4)] and two new green complexes, [Re(III)(S(2)CC(6)H(5))(S(3)CC(6)H(5))(2)] (recently communicated) and [W(VI)S(S(2))(S(2)CC(6)H(5))(2)], were isolated from related reactions.

Synthesis and Reactivity of [TpRh(PPh3)2] (Tp = Hydridotris(pyrazol-1-yl)borate)

The new complex [TpRh(PPh3)2], readily obtained from [RhCl(PPh3)3] and KTp, is a particularly convenient and versatile entry point into the organometallic chemistry of the “TpRh” fragment including complexes bearing alkyne, alkene, carbene, thiocarbamoyl, dithioalkoxycarbonyl, carbon disulfide, and vinyl ligands.