Academic literature on the topic 'Schwefel-Ligand'

The reaction of [Fe(NiSiMe3)2)2] with thiols RSH, elemental sulfur, and neutral ligands L (with sulfur donor atoms, e. g. thiourea derivatives) gives [Fe4S4(SR)2L2] clusters in high yields. The structure of [Fe4S4(2.4.6-(C3H7)3C6H2-S)2(dpdmi)2] (dpdmi: diisopropyldimethyl- imidazolthion) was determined by X-ray crystallography.When [Fe4S4I4]2- is reacted with a large excess of PMePh2 or PMe2Ph [F6S6I2(PMePh2)4] and [Fe6S6l2(PMe2Ph)4]. respectively, are obtained in nearly quantitative yield. Basket-like structures of the [Fe6S6]2+ cores were detected by X-ray structure analysis. While [Fe4S4(SR)4]2- clusters do not react with phosphanes at ambient temperature 2:2 functional­ized species like [Fe4S4(SR)2(tmtu)2] lead to basket-type clusters [Fe6S6(SR)2(PR3)4].

Fe4S4I2(SPPh3)2 (1) was prepared by the reaction of Fe(THF)6Fe4S4I4 (THF = C4H8O). SPPh,. and sulfur in toluene and CH2Cl2. 1 has a lower stability than Fe4S4I42- and decomposes in solvents like THF and CH3CN. The crystal structure of 1 was determined from single crystal X-ray diffraction data. The compound crystallizes in the triclinic space group P1̄ with a = 1025.5(1). b = 1082.4(1), c = 2135.5(3) pm. α = 89.82(1), β - 77.37(1), γ = 73.56(1)°, V = 2214.1×106 pm3 and Z = 2. The [Fe4S4]2+ core of 1 exhibits a slight tetragonal distortion. The mean Fe-S and Fe-Fe distances were found to be 227.6 (225.8-228.7) pm and 273.3 (272.9-274.4) pm, respectively. The Fe-SPPh3 distances (231.6 and 232.1 pm) are longer than the terminal Fe-S bonds in RS coordinated [Fe4S4] clusters. The Fe-I bonds are found at 251.6 and 251.8 pm. respectively.

The reaction of [Fe4S4I2(SC(NMe2)2)2] with racemic trans-1,2-bis(3-methylthioureido)-cyclohexane in tetrahydrofuran (thf) yields [Fe4S4I2(C6H10(NHCSNHMe)2)] · 4 thf (2). 2 crystallizes in the monoclinic space group C 2/c with a = 1471.7(2), b = 1329.7(2), c = 2339.3(3) pm, β = 107.70(1), V = 4362.3 × 106 pm3, Z = 4, R = 0.057. The cluster exhibits C2 symmetry in the solid state. The replacement of the monodentate neutral ligands results in a cluster in which the bifunctional thiourea derivative bridges two different iron sites of the slightly compressed [Fe4S4] core. The most striking feature are the differences of the Fe–Fe distances which are 269.8 pm between thiourea coordinated atoms and 280.7 pm between Fe atoms with iodide ligation. The Fe–S thiourea distance was found to be 229.3 pm.

Tetranuclear clusters Mo4S4(R2PS2)6 (4) (a: R = Et, b: R = Pr) with cubane-like cores are conveniently obtained by reacting equimolar quantities of Mo3S4(Et2PS2)4, Mo(CO)6 and R2P(S)-S-S-P(S)R2. 31P NMR and MS data of 4 are reported and the magnetic properties are discussed. 4a crystallizes triclinically with a = 1159.41(6), b = 1162.77(7), c = 2228.54(14) pm, α = 102.660(3), β = 98.382(4), γ = 98.546(5)°. P1̅, Z = 2. The molecule consists of a distorted Mo4S4 cubane. Each Mo atom is coordinated by six S atoms: three within the cubane, two from a bidentate and one from a chelating dithiophosphinato ligand. Two Mo -Mo distances are short- ened by the chelate to an av. of 278.6 pm, while the av. of the remaining four Mo -Mo distances is 287.9 pm.

Paramagnetic [Ni('NMeS4')]2 1 ('NMeS4'2- = 2.2'-Bis(2-mercaptophenylthio)diethylmethylamine(2-)) was synthesized from Ni(ac)2 and Na2-'N MeS4' and characterized by X-ray structure analysis. In solid state, 1 contains two pseudo-octahedral [Ni('NMeS4')] fragments bridged via thiolate donors. In contrast to the parent complex [Ni('NHS4')]2, the thiolate and thioether donors coordinate cis to the Ni center forming meso [Ni('N MeS4')] fragments of CS symmetry. 1 readily dissociates in solution to give mononuclear [Ni('NMeS4')]. Reaction of [Ni('NMeS4')]2 1 with PMe3 yielded [Ni(PMe3)('NMeS4')] 2, oxidation by iodine gave the Ni(III) complex [Ni(I)('NMeS4')] 3

The diamagnetic tetranuclear cluster complexes Mo3CuS4I(R2PS2)4•C5H5N 2 (a: R=Et, b: R=Pr) are obtained by reaction of Mo3S4L4 (L = R2PS2-) 1 with CuI and pyridine. Each Mo atom of the cubane-type Mo3CuS4 core is chelated by L. Two of the Mo atoms are bridged by the fourth L, while a pyridine ligand completes the coordination sphere of the third Mo atom, and iodine is bonded to the Cu atom. Magnetic, NMR- and MS-spectroscopic data are given. 2b crystallizes in the monoclinic space group P21/n with Z = 4 and lattice parameters a = 21,164(7), b = 10,653(3), c = 25,455(8)Å, and β = 106,25(3)°.

Li[PhS(NSiMe3)2]-0.5 Et2O (1) is prepared by treatment of Me3SiNSNSiMe3 with phenyllithium. The lithium salt 1 reacts with UCl4, ScCl3(THF)3 and NdCl3(THF)2 to give di-, and trisubstituted complexes containing the chelating [PhS(NSiMe3)2] ligand. [PhS(NSiMe3)2]2UCl (2) has been characterized by an X-ray structure determination.

AbstractAt the transition metal sulfur center of [Ru(PPh3)2dttd], (dud2- = 2,3;8,9-dibenzo-1,4,7,10- tetrathiadecane( -2)), the substitution of one PPh3 ligand by anions like N3- or CN- in CH2Cl2 is always coupled with a chloromethylation of one thiolato S atom in dttd2- yielding the [dttd-CH2Cl]- ligand; with N3- conversion of azido into cyano ligands takes place additionally. In the reaction of [Ru(PPh3)2dttd] with covalent azides like Me3SiN3 or HN3, the PPh3 substitution is also coupled with the oxidation of Ru(II) to Ru(III). Thus [Ru(PPh3)2dttd] on reaction with NEt4N3 or NEt4CN in boiling CH2Cl2 yields [Ru(PPh3)(L)(dttd-CH2Cl)], (L = N3-, CN-), whereas with Me3SiN3 or HN3 in addition to [Ru(PPh3)(N3)(dttd-CH2Cl)] the paramagnetic (μeff = 1.58 B.M.) [Ru(PPh3)(N3)(dttd)] is obtained. The very stable [Ru(PPh3)(CN)(dttd-CH2Cl)] forms deeply coloured adducts with H+ as well as [CrCl3(THF)3], AlCl3 and BF3. With Mel it yields [Ru(PPh3)(CN)(Me-dttd-CH2Cl)]I. All compounds have been characterized by elemental analysis as well as spectroscopic means including ESCA; the structure of [Ru(PPh3)(CN)(dttd-CH2Cl)] has been solved by X-ray structure analysis.

The reaction of [FeI2L2] (1; L = SC(NMe2)2) with KSR (R = 2,4,6-i-Pr3C6H,) yields [Fe(SR)2L2] · PhMe (2).Oxidation of the thiolate ligands of 2 with ((Me2N)2CSSC(NMe2)2)2+ affords the cationic complexes [Fe(SR)L3]+ and [FeL4]2+, which were isolated as tetraphenylborate salts.A mixed ligand neutral iron sulfur cluster [Fe4S4(SR)2L2] (3) has been synthesized by the reaction of 2 with elemental sulfur. 3 is a precursor for cationic clusters which are obtained via the above-mentioned oxidation. The structures of 2 and 3 were determined from single crystal X-ray diffraction data.2 crystallizes in the monoclinic space group C2/c with a = 1807.8(1), b = 1000.6(1), c = 2946.0(2) pm, β = 101.16(1), V = 5227.6 × 106 pm3, Ζ = 4, R = 0.067. The complex exhibits C2-symmetry and a distorted tetrahedral coordination of Fe(II) (S–Fe–S angles between 101.7 and 125.7). The Fe–Sthiourea and Fe–Sthiolate bond lengths were found to be 240.3(2) and 231.5(1) pm, respectively.3: triclinic, P1, a= 1020.2(2), b = 1035.3(2), c = 1402.1(2) pm, α = 73.50(1), β = 70.47(1), γ=84.38(1),V= 1338.2 × 106pm3,Z= 1, R = 0.039.3 shows a slightly compressed Fe4S4 core structure. The Fe– Fe distances range from 269.1 to 278.1 pm. The shortest and longest distances are observed between those Fe atoms which have two thiourea and two thiolate ligands, respectively.

Die Entwicklung neuer Verfahren für die Rückführung von Palladium aus Altmaterialien, wie gebrauchten Autoabgaskatalysatoren, in den Stoffstromkreislauf ist sowohl aus ökologischer als auch ökonomischer Sicht erstrebenswert. In dieser Arbeit wurden neue Flüssig-Flüssig- und Fest-Flüssig-Extraktionsmittel entwickelt, mit denen Palladium(II) aus einer oxidierenden, salzsauren Laugungslösung, die neben Palladium auch Platin und Rhodium sowie zahlreiche unedle Metalle enthält, zurückgewonnen werden kann. Die neuen Extraktionsmittel ungesättigte monomere 1,2-Dithioether und oligomere Ligandenmischungen mit vicinalen Dithioether-Einheiten – sind im Gegensatz zu vielen in der Literatur aufgeführten Extraktionsmitteln hochselektiv. Aufgrund ihrer geometrischen und elektronischen Präorganisation bilden sie mit Palladium(II) stabile quadratisch-planare Chelatkomplexe. Für die Entwicklung des Flüssig-Flüssig-Extraktionsmittels wurde eine Reihe von ungesättigten 1,2-Dithioetherliganden dargestellt, welche auf einer starren 1,2-Dithioethen-Einheit, die in ein variierendes elektronenziehendes Grundgerüst eingebettet ist, basieren und polare Seitenketten besitzen. Neben der Bestimmung der Kristallstrukturen der Liganden und ihrer Palladiumdichlorid-Komplexe wurden die elektro- und photochemischen Eigenschaften, die Komplexstabilität und das Verhalten in Lösung untersucht. In Flüssig-Flüssig-Extraktionsuntersuchungen konnte gezeigt werden, dass einige der neuen Liganden industriell genutzten Extraktionsmitteln durch eine schnellere Einstellung des Extraktionsgleichgewichts überlegen sind. Anhand von Kriterien, die für eine industrielle Nutzbarkeit entscheidend sind, wie: guter Oxidationsbeständigkeit, einer hohen Extraktionsausbeute (auch bei hohen Salzsäurekonzentrationen der Speiselösung), schneller Extraktionskinetik und einer hohen Selektivität für Palladium(II) wurde aus der Reihe der sechs Liganden ein geeignetes Flüssig-Flüssig-Extraktionsmittel ausgewählt: 1,2-Bis(2-methoxyethylthio)benzen. Mit diesem wurde ein praxisnahes Flüssig-Flüssig-Extraktionssystem entwickelt. Nach der schrittweisen Adaption der wässrigen Phase von einer Modelllösung hin zu der oxidierenden, salzsauren Laugungslösung erfolgte die Auswahl eines geeigneten großtechnisch, einsetzbaren Lösemittels (1,2-Dichlorbenzen) und eines effizienten Reextraktionsmittels (0,5 M Thioharnstoff in 0,1 M HCl). Die hohe Palladium(II)-Selektivität dieses Flüssig-Flüssig-Extraktionssystems konnte verifiziert und seine Wiederverwendbarkeit und Praxistauglichkeit unter Beweis gestellt werden. Weiterhin wurde gezeigt, dass sich beim Kontakt mit oxidierenden Medien aus dem Dithioether 1,2-Bis(2-methoxyethylthio)benzen geringe Mengen des Thioethersulfoxids 1-(2-Methoxyethylsulfinyl)-2-(2-methoxyethylthio)benzen bilden. Dieses wird im sauren Milieu protoniert und beschleunigt die Extraktion wie ein Phasentransferkatalysator, ohne jedoch die Palladium(II)-Selektivität herabzusetzen. Die Kristallstruktur des Palladiumdichlorid-Komplexes des Tioethersulfoxids zeigt, dass der unprotonierte Ligand Palladium(II), analog zum Dithioether, über die chelatisierenden Schwefelatome koordiniert. Verschiedene Mischungen von Oligo(dithioether)-Liganden und der monomere Ligand 1,2-Bis(2-methoxyethylthio)benzen dienten als Extraktionsmittel für Fest-Flüssig-Extraktionsversuche mit SIRs (solvent impregnated resins) und wurden zu diesem Zweck auf hydrophilem Kieselgel und organophilem Amberlite® XAD 2 adsorbiert. Die Oligo(dithioether)-Liganden basieren auf 1,2-Dithiobenzen oder 1,2-Dithiomaleonitril-Einheiten, welche über Tris(oxyethylen)ethylen- oder Trimethylen-Brücken miteinander verknüpft sind. Mit Hilfe von Batch-Versuchen konnte gezeigt werden, dass sich strukturelle Unterschiede - wie die Art der chelatisierenden Einheit, die Art der verbrückenden Ketten und das Trägermaterial - auf die Extraktionsausbeuten, die Extraktionskinetik und die Beladungskapazität auswirken. Die kieselgelhaltigen SIRs stellen das Extraktionsgleichgewicht viel schneller ein als die Amberlite® XAD 2-haltigen. Jedoch bleiben die Extraktionsmittel auf Amberlite® XAD 2, im Gegensatz zu Kieselgel, dauerhaft haften. Im salzsauren Milieu sind die 1,2-Dithiobenzen-derivate besser als Extraktionsmittel geeignet als die 1,2-Dithiomaleonitrilderivate. In Säulenversuchen mit der oxidierenden, salzsauren Laugungslösung und wiederverwendbaren, mit 1,2-Dithiobenzenderivaten imprägnierten, Amberlite® XAD 2-haltigen SIRs zeigte sich, dass für die Realisierung hoher Beladungskapazitäten sehr geringe Pumpraten benötigt werden. Trotzdem konnte die gute Palladium(II)-Selektivität dieser Festphasenmaterialien demonstriert werden. Allerdings wurden in den Eluaten im Gegensatz zu den Eluaten, die aus Flüssig-Flüssig-Extraktion resultierten neben dem Palladium auch geringe Mengen an Platin, Aluminium, Eisen und Blei gefunden.
The development of new processes for the recovery of palladium from recycling materials like spent automotive catalysts is of economic and ecologic interest. In this thesis new solvent and solid phase extractants have been designed, which are suitable for the recovery of palladium(II) from an oxidising hydrochloric leach liquor that does not only additionally contain platinum and rhodium but also a number of base metals. In contrast to many extractants described in the literature these new extractants – unsaturated monomeric dithioethers as well as oligomeric mixtures of ligands with vicinal dithioether units – are highly selective for palladium(II). Due to their geometric and electronic preorganisation they form stable square-planar chelate complexes with palladium(II). For the development of the solvent extractant a series of unsaturated dithioethers, which are based on a rigid 1,2-dithioethene unit that is imbedded in an electron-withdrawing backbone, with polar end-groups has been synthesised. In addition to the determination of the crystal structures of the ligands and their dichloridopalladium complexes, the electro- and photochemical properties, the complex stabilities and the behaviour in solution have been investigated. Solvent extraction experiments showed the superiority of some of our ligands over conventionally used extractants in terms of their very fast reaction rates. Considering criteria that are essential for industrial utilisation like: robustness towards oxidation, achieving of high extraction yields (even at a high hydrochloric acid content of the leach liquor), fast extraction kinetics and a high selectivity for palladium(II), 1,2-bis(2-methoxyethylthio)benzene was selected as the extractant of choice. Building on this a solvent extraction system close to industrial practice was devised. After stepwise adaption of the aqueous phase from a model solution to the oxidising hydrochloric leach liquor, the selection of a diluent suitable for commercial operations (1,2-dichlorobenzene) and of an efficient stripping agent (0.5 M thiourea in 0.1 M HCl) has been accomplished. The high selectivity of that solvent extraction system for palladium(II) could be verified and its reusability and suitability for practical application have been proven. Further it was shown that small amounts of the thioether sulfoxide 1-[(2-methoxyethyl)sulfanyl]-2-[(2-methoxyethyl)sulfinyl]benzene form when the dithioether ligand 1,2-bis(2-methoxyethylthio)benzene gets in contact with oxidising media. Under acidic conditions this thioether sulfoxide gets protonated and accelerates the extraction like a phase transfer catalyst; without decreasing the selectivity for palladium(II). The molecular structure of the corresponding dichloridopalladium complex reveals that the nonprotonated ligand coordinates palladium(II) in a similar manner to the dithioether via the chelating sulfur atoms. Mixtures of oligo(dithioether) ligands and the monomeric 1,2-bis(2-methoxyethylthio)benzene have been adsorbed on silica gel and amberlite® XAD 2. These SIRs (solvent impregnated resins) have been used for solid phase extraction experiments. The oligo(dithioether) ligands are based on 1,2- dithiobenzene or 1,2-dithiomaleonitrile units, which are connected via tris(oxyethylene)ethylene or trimethylene chains. With the help of batch experiments it could be shown how structural differences, like the chelating unit, the kind of linking chain and the type of supporting material, impact the extraction yield, kinetics and loading capacity. The SIRs containing silica gel establish the extraction equilibrium much faster than those containing amberlite® XAD 2. On the other hand, the extractants permanently remain on amberlite® XAD 2, in contrast to silica gel. In a hydrochloric medium 1,2-dithiobenzene derivatives are better extractants than 1,2-dithiomaleonitrile derivatives. In column experiments with the oxidising hydrochloric leach liquor and reusable SIRs based on 1,2-dithiobenzene derivatives impregnated into amberlite® XAD 2, it appeared that for the implementation of high loading capacities very low flow rates are required. The selectivity for palladium(II) of these solid phase extractants could be demonstrated, although the eluates, in contrast to the eluates gained from the solvent extraction experiments, contained not only palladium but also small amounts of platinum, aluminium, iron and lead.