Search

Thiolate protected metal clusters are valuable precursors for the design of tailored nanosized catalysts. Their performance can be tuned precisely at atomic level, e.g. by the configuration/ type of ligands or by partial/complete removal of the ligand shell through controlled pre-treatment steps. However, the interaction between the ligand shell and the oxide support, as well as ligand removal by oxidative pre-treatment, are still poorly understood. Typically, it was assumed that the thiolate ligands are simply converted into SO 2 , CO 2 and H 2 O. Herein, we report the first detailed observation of sulfur ligand migration from Au to the oxide support upon deposition and oxidative pre-treatment, employing mainly S K-edge XANES. Conse- quently, thiolate ligand migration not only produces clean Au cluster surfaces but also the surrounding oxide support is modified by sulfur-containing species, with pronounced effects on catalytic properties

© 2017 Gold surfaces are widely used in electrochemistry while gold nanoparticles have very many uses, with both the surfaces and the particles often being protected by sulfur-bound organic ligands. The ligands not only provide chemical stability but also directly participate in many desired processes. This review considers the diversity of known atomic structures for gold–sulfur interfaces, how these structures facilitate a diversity of mechanisms in electrochemical applications, and why this is possible based on recent advances in the basic understanding of the electronic structure of gold–sulfur bonds. Believed once to be Au(I)-thiolate in character and hence distinctly different to physisorbed thiols and disulfides, chemisorbed bonds are shown to be Au(0)-thiyls instead. A wide range of in situ STM electrochemical and other data is interpreted from this perspective.

Correction for ‘Tridentate tripodal sulfur ligand as a stable molecular surface anchor for the fabrication of oligonucleotide-gold based label-free biosensors’ by Huancai Yin et al., Anal. Methods, 2017, 9, 600–608.

The solid-state structures of compounds PPh2CH2SPh (1) and PPh2C6H4SMe (2) were determined by single crystal X-ray diffraction. Experimental results on the molecular structures of compounds 1 and 2 were supported by Hirshfeld surface analysis and Density Functional Theory (DFT). The computed values calculated at DFT level using B3LYP function with 6-311++G (3df, 3pd) (P, S) and 6-31G* (C, H) basis sets are in good agreement with the experimental results.

This review is focused on the chemistry of titanocene sulfide compounds. The linking element for all compounds discussed in this review is the presence of a bent titanocene fragment consisting of two aromatic cyclopentadienyl rings and one electron deficient central titanium atom coordinated between them. Several types of sulfur ligands bonding to titanocene fragment, such as hydrosulfide, sulfide or thiolate are described, as well as the various types of sulfur ligand functions in titanocene complexes have been observed. The titanocene sulfide chemistry is more than fifty years old, but since it is still evolving, it offers a plethora of surprises and challenges.

Catalytic processes involving cooperativity have seen tremendous progress in recent years and impressive new synthetic methodologies have been developed. Inspired by the cooperative heterolytic H2 splitting in [NiFe] hydrogenases, Ohki and Tatsumi designed cationic ruthenium thiolate complexes with a tethered sulfur ligand. Over the last decade, we have demonstrated the facile activation of main-group hydrides such as hydrosilanes, hydroboranes, DIBAL–H, and hydrostannanes by the Ru–S bond in Ohki–Tatsumi complexes. This account illustrates these E–H bond activations and highlights selected catalytic applications, particularly dehydrocouplings, of the generated main-group electrophiles.

The protonation of trans-[Os(OMe)2{N(Pri2PS)2}2] (1) with HBF4, followed by treatment with NH3(g) afforded the oxo-bridged dimer [Os2(μ-O){N(Pri2PS)2}4F2] (2). Reaction of 2 with Ag(OTf) (OTf− = triflate) gave the heterometallic Os(IV)/Ag(I) complex [Os2(μ-O){N(Pri2PS)2}4F2(AgOTf)2] (3), in which each Ag(OTf) moiety binds to three sulfur atoms of two [N(Pri2PS)2]− ligands. The solid-state structures of complexes 2 and 3 have been established by X-ray crystallography.

This review is focused on the chemistry of titanocene sulfide compounds. The linking element for all compounds discussed in this review is the presence of a bent titanocene fragment consisting of two aromatic cyclopentadienyl rings and one electron deficient central titanium atom coordinated between them. Several types of sulfur ligands bonding to titanocene fragment, such as hydrosulfide, sulfide or thiolate are described, as well as the various types of sulfur ligand functions in titanocene complexes have been observed. The titanocene sulfide chemistry is more than fifty years old, but since it is still evolving, it offers a plethora of surprises and challenges.

The molecular structure of [Cp*2Mo2P2S3] (1; Cp* = η5-C5Me5) has been reinvestigated. In DFT studies a series of various positional isomers A−E have been calculated for the model complex [(C5H5)2Mo2P2S3]. The energetically favored isomer [Cp*2Mo2(μ,η2:2-PS)2(μ-S)] (1B) reacts with W(CO)5THF to give [Cp*2Mo2P2S3·W(CO)5] (2). X-ray diffraction analysis of 2 confirms the presence of two η2:2-PS dumbbells and one singly bridging sulfur ligand, the W(CO)5 fragment being coordinated at one of the P atoms. Arrangement B is also found in the structure of the diadduct [Cp°2Mo2P2S3{W(CO)5}2] (3; Cp° = t-BuMe2C5H2), which is more stable than its Cp* analogue. 31P solid-state MAS NMR spectroscopic studies of 1 and 2 confirm the existence of only one isomer, but reveal disorder phenomena in the solid state within the cyclo-P2S3 middle deck. Addition of excess W(CO)5THF to 1 proceeds via elusive [Cp*2Mo2P2S3{W(CO)5}2] to give the cluster [{Cp*2Mo2W(CO)3(μ2,η2:2-PS)(μ3,η1:1:2-PS)(μ3-S)}{W(CO)5}2] (5). The molecular stru...

6-Ethynylferrocene-2,11-dithia[3.3]orthocyclophane has been prepared by cross-coupling 6-bromo-2,11-dithia[3.3]orthocyclophane to ethynylferrocene under Sonogashira conditions. The dynamic structure in solution of this potential ligand has been examined by variable temperature NMR whereas its solid state structure has been determined by X-ray diffraction studies. The electrochemical parameters of this cyclophane have also been examined.

The sulfur-rich iron carbonyl dimer complexes [Fe(CO) 2 (S′ Si S 2 )] 2 ( 2 ), and [Fe(CO)(S′ Si S 2 )] 2 ( 3 ) have been prepared. The [2Fe–2S] cores of the new complexes are planar. The binding mode of the tridentate sulfur ligand in complex 2 is facial with a S(thiolate)–Fe–S(thiolate) angle of 92°, while in complex 3 , the S′ Si S 2 ligand binds the metal with a S(thiolate)–M–S(thiolate) angle of 120°. The Fe–Fe distance is reduced from 3.45 A in complex 2 to 2.78 A in the 32 electron dimer complex 3 . Complexes 2 and 3 are at equilibrium in solution and can be readily interconverted by addition or removal of CO.

Addition of 1 equiv. (Ph3P)Au(ClO4) (formed by ion exchange of Ph3PAuCl with AgClO4) to [naphthalene-1,8-bis(thiolato)]bis (triphenylphosphane) platinum results in the formation of a novel dimetallic cationic complex with a (triphenylphosphane)gold moiety attached to the sulfur of the naphthalene-1,8-bis(thiolato) ligand. NMR spectroscopic evidence suggests that this gold-containing fragment is fluxional in its bonding and X-ray crystallography confirms the asymmetric complex, which shows this gold atom attached to one of these sulfur atoms. Addition of more than 1 equiv. (Ph3P)Au-(ClO4) results in the formation of a tetrametallic sandwich complex with two bridging gold atoms between the sulfur atoms of the two PtS2C3 rings. Tri- and tetrametallic silver-containing complexes can be prepared by addition of 0.5 and 1 equiv. AgClO4 to (Ph3P)(2)Pt(S2C10H6), respectively. (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007.

Potassium 1,3-dipyrrolidinopropan-2-O-xanthate (LK), and its complexes with Co(II), Ni(II) and Cu(I) have been prepared and characterized as [CoL2(H2O)2] · 2H2O, [NiL2(H2O)2] and CuL · 2H2O by FT-IR, 1H and 13C NMR spectroscopies, elemental analyses, magnetic susceptibility and TGA techniques.

Treatment of [Cp*RuCl2]x (Cp* = η5-C5Me5) with K[N(Ph2PS)2] afforded [Cp*Ru{N(Ph2PS)2}Cl] (1). Reduction of 1 with Li[BEt3H] gave the 16-electron half-sandwich Ru(II) complex [Cp*Ru{N(Ph2PS)2}] (2). Complexes 1 and 2 have been characterized by X-ray crystallography. The Ru–Cp*(centroid) and average Ru–S distances in 1 are 1.827 and 2.3833(5) A, respectively. The corresponding bond distances in 2 are 1.739 and 2.379(1) A. Treatment of 2 with 2-electron ligands L afforded the adducts [Cp*Ru{N(Ph2PS)2}L] (L = CO (3), 2,6-Me2C6H4NC (4), MeCO2C CCO2Me (5)). Oxidation of 2 with tetramethylthiuram disulfide gave the Ru(IV) complex [Cp*Ru{S2CNMe2}2][N(Ph2PS)2] (6). The Ru–Cp*(centroid) and average Ru–S distances in 6 are 1.897 and 2.387(1) A, respectively.

The silver(I) complexes of 2,2′,3,3′-tetrahydro-4,4′-dithia-1,1′-binaphthylidene (ttp) having a nine-member SAgS chelating ring, [Ag(ttp)(ClO4)]n (1) and [Ag2(ttp)2(CF3SO3)2]n (2), have been synthesized and characterized by single-crystal X-ray diffraction. The ttp is found to offer a potential coordination site for complexation, which can be utilized to generate an interesting array of silver(I) complexes with a one-dimensional chain and a chiral chain.

Reaction of a 1, 2, 4, 5-tetraoxane with cysteinate-iron in the presence of excess methyl cysteinate led to formation of sulfuralkylated methyl cysteinate in 33% yield, illustrating a possible mechanism for tetraoxanes'antimalarial action.

A novel potential bidentate sulfur ligand, K2[S2CNHCOCH2CN] and its complexes with first row divalent transition metal ions of the type, M(phen)L, [M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Pd(II), L = S2CNHCOCH2CN and phen = 1,10-phenanthroline] have been synthesised and characterised. On the basis of IR and 1H NMR an enol form is found in the case of ligand and its complexes in the solid state whereas the complexes exist predominantly in the keto form in solution. Electronic spectra and magnetic measurement data indicate that the Ni(II), Cu(II) and Pd(II) complexes have a square-planar geometry but the others have a distorted-tetrahedral structure.

Resonance Raman and IR spectroscopic measurements of the two diazene-bridged systems [{Fe‘NHS4'}2(N2H2)] (‘NHS4'2- = 2,2‘-bis(2-mercaptophenylthio)diethylamine(2−)) (I) and [{Fe‘S4'(PPr3)}2(N2H2)] (‘S4'2- = 1,2-bis(2-mercaptophenylthio)ethane(2−)) (II) including 2H- and 15N-isotopomers are combined with a normal coordinate analysis (NCA) in order to describe the vibrational properties of diazene coordinated to Fe(II)−sulfur centers. Eight of the 12 normal modes of the Fe-N2H2-Fe unit have been identified by their isotope shifts. Most of the Raman-active diazene vibrations are resonance enhanced with respect to the 600 nm transition providing further support to the assignment of this band as Fe(d) to diazene(π*) charge-transfer (MLCT) transition. The force constant for the N−N bond of 7.7 mdyn/A corresponds to a N−N bond order of about 1.5 and indicates that the diazene unit is moderately activated. The force constant of the Fe−N bond of 1.8 mdyn/A is about 2.5 times as large as for a simple σ-bond. These ...

Complexes of Au(I) and Cu(I) with 1-(thiomethyl)-2-(diphenylphosphino)ethane (PSMe) have been prepared; the two products have the same general formula MCl(PSMe). The structure of the gold complex has been determined by X-ray crystallography. AuCl(PSMe) crystallizes in the monoclinic system, space group P2 1 /c, a= 11.618(9), b = 11.664(7), c = 13.013(8) A , V = 1615 A , β = 113.6(1) °, Z = 4 . The complex is linear with PAuCl = 177.9(1)°. The copper complex has been studied by mass, IR and NMR spectroscopies, in view of the results so obtained we have postulated a dinuclear structure with a chloride bridge for this compound.

The dinuclear complex [{Pd(µ-SPPh2)(C6F5)(PPh3)}2] reacted with the cationic precursors [PdL(Me2CO)2]+[L = 2-(dimethylaminomethyl)phenyl-C1,N, quinolin-8-ylmethyl-C,N or phenylazophenyl-C1,N] and with the neutral precursors [M(C6F5)2(thf)2](M = Pd or Pt, thf = tetrahydrofuran) to give the corresponding cationic homotrinuclear complexes [Pd3(µ3-SPPh2)2(C6F5)2L(PPh3)2]ClO4(L = C6H4CH2NMe2-2 1, NC9H6CH2-8 2 or PhNNC6H43) and the neutral homo- and hetero-trinuclear complexes [Pd2M(µ3-SPPh2)2(C6F5)4(PPh3)2](M = Pd 4 or Pt 5) in which the [SPPh2]– group acts as a triply-bridging ligand. Complexes 1–5 have been characterized by spectroscopic methods (IR; 1H, 19F and 31P-{1H} NMR) and the molecular structure of [Pd3(µ3-SPPh2)2(C6F5)2(C6H4CH2NMe2–2)(PPh3)2]ClO41 has been determined crystallographically. Complex 1·0.8CH2Cl2 crystallizes in the monoclinic system, space group P21/c, a= 14.185(3), b= 21.589(4), c= 27.440(5)A, β= 104.95(3)° and Z= 4. The model refined to final values of R= 0.0702 and R′= 0.0849 for 5989 observed reflections [F > 4.0σ(F)] and 860 parameters. The structure shows that the [Pd(µ-SPPh2)(C6F5)(PPh3)]2 unit behaves as a cyclic bidentate sulfur ligand, co-ordinated to the [Pd(C6H4CH2NMe2-2)]+ group through the two S atoms. The central Pd3(SPPh2)2 cage contains two µ3-SPPh2 ligands linking the three palladium atoms.

In order to investigate the potential conversion of coordinated NO into N2 ligands at Ru sulfur centers, the cationic Ru nitrosyl complex meso-[Ru(NO)('S5')]Br (1)** was synthesized by template alkylation of [NBu4][Ru(NO)('S2')2]** with (BrC2H4)2S. 1 is reactive towards nucleophiles. Reaction with azide yields N2O, N2 and [Ru('S5')]2 (2), reaction with LiNH2, NH3 and NEt3 leads to C-S bond cleavage in the 'S5' ligand of 1 and to the formation of a Ru nitrosyl vinylthioetherthiolate complex.

The power of proline: Bold amino acid substitutions in sensitive protein regions are frequently unproductive, while more subtle mutations can be sufficient to bring about dramatic changes. But introducing proline at the residue next to the sulfur ligand in P450(BM3) (CYP102A1) has the unexpected and desirable effect of enhancing the activity of this fatty acid hydroxylase with a broad range of non-natural substrates, as illustrated by the figure.

Metal-sulfur ligand redox interplay, induced internal electron transfer reactions, and the generation of dithiolene and organosulfur ligands in the reactions of metal-sulfur compounds with alkynes are important and useful facets of early transition metal-sulfur chemistry. This review focuses on developments in these areas over the past 30 years.

Substitution reactions at the nickel site of the cubane-type cluster [(Ph3P)NiFe3S4(LS3)]2- (2) have been investigated in the course of a synthetic approach to the C-clusters of CODH. Reaction of 2 with RS- or toluene-3,4-dithiolate affords [(RS)NiFe3S4(LS3)]3- (R = Et (5), H (6)) or [(tdt)NiFe3S4(LS3)]3- (7), demonstrating that anionic sulfur ligands can be bound at the NiII site. Clusters 5 and 6 contain tetrahedral Ni(micro3-S)3(SR) sites. Cluster 7 is of particular interest because it includes a cubanoid NiFe3(micro2-S)(micro3-S)3 core and an approximately planar Ni(tdt)(micro3-S)2 unit. The cubanoid structure is found in all C-clusters, and an NiS4-type unit has been reported in C. hydrogenoformans CODH. Clusters 5/6 are formulated to contain the core [NiFe3S4]1+ identical with Ni2+ (S = 1) + [Fe3S4]1- (S = 5/2) and 7 the core [NiFe3S4]2+ identical with Ni2+ (S = 0) + [Fe3S4]0 (S = 2) on the basis of structure, 57Fe isomer shifts, and 1H NMR isotropic shifts. Also reported are [(EtS)CuFe3S4(LS3)]3- (9) and [Fe4S4(LS3)(tdt)]3- (11). The structures of 5-7, 9, and 11 are presented. Cluster 11, with a five-coordinate Fe(tdt)(micro3-S)3 site, provides a clear structural contrast with 7, which is currently the closest approach to a C-cluster but lacks the exo iron atom found in the NiFe4S4,5 cores of the native clusters. (CODH = carbon monoxide dehydrogenase, LS3 = 1,3,5-tris((4,6-dimethyl-3-mercaptophenyl)thio)-2,4,6-tris(p-tolylthio)benzene(3-), tdt = toluene-3,4-dithiolate).

Metallothioneins (MTs) are low molecular weight cysteine-rich proteins able to coordinate metal ions. Metal-MT chelation is mainly achieved by formation of metal-thiolate clusters but also by non-proteic ligands, such as chloride and sulfìde ions. Plant Quercus suber metallothionein (QsMT) differs from animal MTs in sequence organisation consisting of two Cys-rich regions separated by a Cys-devoid spacer domain containing one His residue. In contrast with the current knowledge on the 3D structure of animal MTs, there is an appalling lack of structural data on plant MTs. Zn+2 and Cd+2 complexes of QsMT were obtained by in vivo synthesis, in order to obtain physiological representative aggregates, and characterized by spectrometric and spectroscopic methods. The composition of the metallic aggregates were determined by ICP-AES, GC-FPD and ESI-MS. The results indicated that Cd-QsMT contains significantly higher amounts of metal and sulfìde ions that Zn-QsMT. Raman andir measurements revealed that, oppositely to what is known for other MTs, metal-QsMT contains significant amounts of secondary structures, predominantly B-sheet and B-turns elements, whereas it lacks a-helices. Interestingly, the properties of the metallic clusters formed are strongly dependent on the metal bound, Zn+2 or Cd+2. According to analytical results, the Raman spectra showed that Cd-QsMT is able to inglobe an the higher content of sulfide ions than Zn-QsMT, and suggested different structures of the complexes depending on the metal bound . Raman spectra also evidenced the participation of His in metal chelation in Cd-QsMT but not in Zn-QsMT. The differences observed between Zn+2 and Cd+2 metallic clusters suggest for QsMT a hybrid homeostatic/detoxificating role which would be developed through the acquisition of novel properties and metal-binding abilities depending on the metal coordinated.

Zn- and Cd-complexes of Quercus suber metallothionein (QsMT) were obtained by in vivo-synthesis, in order to obtain physiologically representative aggregates, and characterized by spectrometric and spectroscopic methods. The secondary structure elements and the coordination environments of the metal binding sites of the two aggregates were determined, as well as the main metal-containing species formed. The results obtained from the analysis of the Raman and IR spectra reveal that these metal-MT complexes predominantly contain β-sheet elements (about 60%), whereas they lack α-helices. These structural features slightly depend on the divalent metal bound. In particular, CdII binding to QsMT induces a slight increase of the β-sheet percentage, as well as a decrease in β-turn elements with respect to ZnII binding. Conversely, the in vivo capability of QsMT to inglobe metal and sulfide ions is metal-depending. Spectroscopic vibrational data also confirm the presence of sulfide ligands in the metal clusters of both Zn- and Cd-QsMT, while the participation of the spacer His residue in metal coordination was only found in Cd-QsMT, in agreement with the CD results. Overall data suggest different coordination environments for ZnII and CdII ions in QsMT. © 2007 Wiley Periodicals, Inc. Biopolymers 86: 240–248, 2007. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com