Thioamide Complexes Research Articles

Palladium(II) O^S thioamide complexes catalyzed Guerbet type reaction: β-Alkylation of cyclohexanol with primary alcohols

Pd(II)-PPh3 complexes containing salicylaldehyde based thioamide ligands (1–3) have been synthesized and characterized by analytical and spectroscopic (FT-IR, UV–Visible, HR-MS and NMR) techniques. Spectroscopic methods revealed square planar geometry for all the complexes. These complexes were tested as catalysts for Guerbet-type reaction i.e. dialkylation of cyclohexanol with primary alcohols. The reaction conditions were optimized. Complex 1 bearing morpholinyl group emerged as the best catalyst, and it was used for extending the scope of the reaction to several substituted primary alcohols. The dialkylated products were isolated using column chromatography and confirmed using GC–MS and 1H NMR spectroscopy.

Half-sandwich Ru(II)-thioamide complexes as catalysts for one pot synthesis of aromatic 1,5-diketones

Four Ru(II)-arene thioamide complexes of the type [(η6-cymene)Ru(PPh3)(L)]+ (L = bidentate monoanionic thioamide ligand) have been synthesized and isolated as their hexafluorophosphate salts. All these complexes are fully characterized by spectroscopic methods. Molecular structures of the ligands (HL2 and HL3) and complex (3) were determined by single crystal X-ray crystallography. The ligands coordinated to Ru center through phenolic O and thioamide S atoms. All the four complexes were tested as catalysts in the one pot synthesis of 1,5-diketones from aromatic ketones and alcohols in the presence of KOtBu, and the products were analyzed by GC/GC–MS/1H NMR. Complexes 1 and 2 behaved as catalysts to produce 1,5-diketones while complexes 3 and 4 catalyzed the reactions to form alkylated ketones. Scope of the reaction was extended to various substituted alcohols and ketones to prepare 1,5-diketones with catalyst 1.

Rosetta Machine Learning Models Accurately Classify Positional Effects of Thioamides on Proteolysis.

Thioamide substitutions of the peptide backbone have been shown to stabilize therapeutic and imaging peptides toward proteolysis. In order to rationally design thioamide modifications, we have developed a novel Rosetta custom score function to classify thioamide positional effects on proteolysis in substrates of serine and cysteine proteases. Peptides of interest were docked into proteases using the FlexPepDock application in Rosetta. Docked complexes were modified to contain thioamides parametrized through the creation of custom atom types in Rosetta based on ab intio simulations. Thioamide complexes were simulated, and the resultant structural complexes provided features for machine learning classification as the decomposed values of the Rosetta score function. An ensemble, majority voting model was developed to be a robust predictor of previously unpublished thioamide proteolysis holdout data. Theoretical control simulations with pseudo-atoms that modulate only one physical characteristic of the thioamide show differential effects on prediction accuracy by the optimized voting classification model. These pseudo-atom model simulations, as well as statistical analyses of the full thioamide simulations, implicate steric effects on peptide binding as being primarily responsible for thioamide positional effects on proteolytic resistance.

Pyrrole thioamide complexes of organo-rhodium(III), -iridium(III) and -ruthenium(II)

Reactions of the pentamethylcyclopentadienyl complexes [(η5-Cp*)MCl2]2 (M = Rh, Ir) and the ruthenium arene complex [(η6-C6Me6)RuCl2]2 with pyrrole-2-thioamide ligands (containing various substituents on the pyrrole ring) and triethylamine base were investigated. A set of new dinuclear complexes were obtained in which the pyrrole thioamide ligand bonds as a dianion, through the deprotonated pyrrole, and the sulfur atom bridging the two metal centres, as confirmed by a X-ray structure determination on an iridium derivative. When triphenylphosphine was included in the reaction mixture, mononuclear complexes were obtained, with the pyrrole thioamide dianion ligand coordinating through sulfur and the pyrrole nitrogen, forming a five-membered chelate ring. The complexes were characterised by NMR and IR spectroscopies, and ESI mass spectrometry. A preliminary investigation of the activity of a selection of compounds towards A549 (adenocarcinomic human alveolar basal epithelial) cells was also carried out.

Pyrrole thioamide complexes of the d8 metals platinum(II), palladium(II) and gold(III)

Reactions of the cycloaurated gold(III) complexes [AuCl2(2-benzylpyridyl)] and [AuCl2(C6H4CH2NMe2)] with a set of pyrrole-2-thioamide ligands, containing various substituents on the pyrrole ring, gave a series of new gold(III) pyrrole thioamide complexes. X-ray crystal structures on two complexes indicate that the pyrrole thioamide ligand is coordinated through the deprotonated pyrrole nitrogen, as well as the sulfur atom of the deprotonated thioamide group, forming five-membered chelate ring complexes. In both complexes, the two highest trans-influence donor atoms (C and S) are mutually cis. Related sets of platinum(II) and palladium(II) pyrrole thioamide complexes were similarly prepared by reactions of cis-[PtCl2(PPh3)2] and [PdCl2(dppe)] (dppe = Ph2PCH2CH2PPh2)] respectively. The complexes were characterised by NMR and IR spectroscopies, and ESI mass spectrometry. A preliminary investigation of the activity of a selection of compounds towards A549 (adenocarcinomic human alveolar basal epithelial) cells was also carried out.

Structural architectures and biological properties of main group bismuth(III) iodide complexes with heterocyclic thioamides

A series of mononuclear, dinuclear and polynuclear bismuth(III) iodide complexes (1–5) bearing heterocyclic thioamide ligands, 2-mercapto-3,4,5,6-tetrahydro-pyrimidine (tHPMT), 2-mercapto-benzimidazole (MBZIM), 2-mercapto-1-methylimidazole (MMI), 2-mercaptobenzothiazole (MBZT) and 2-mercaptopyridine (PYT), have been synthesized and characterized by melting point, elemental analysis, FT-IR spectroscopy, Raman spectroscopy, 1H, 13C NMR spectroscopy, UV–Vis spectroscopy and Thermal Gravimetry-Differential Thermal Analysis (TG-DTA). Moreover, the crystal structures of 1–5 have been also determined with single crystal X-ray diffraction analysis. The use of the above mentioned heterocyclic thioamide ligands have allowed synthesis of the first examples of bismuth(III) iodide thioamide complexes. {[BiI3(tHPMT)3]} (1) is the first structural example of a neutral mononuclear bismuth(III) iodide complex with octahedral geometry around the bismuth(III) ion with meridional conformation. {[BiI2(µ2-I)(MBZIM)2]2} (2) is the first example of a dinuclear bismuth(III) iodide complex with octahedral geometry around the bismuth(III) ion with trans-S/cis-I arrangement. {[BiI(µ2-I)2(MMI)]n} (3) and {[BiI(µ2-I)2(MBZT)]n·CH3OH} (4) are the first examples of the polynuclear bismuth(III) iodide complexes with octahedral geometry around the bismuth(III) ions. The ligand molecules are coordinated via the thione sulfur atoms in both complexes but in complex 3, ligand molecules are trans to each other in polymeric chain while, in complex 4, ligand molecules are cis to each other in polymeric chain. {[BiI(µ2-S,N-PYT)2]n} (5) is the first example of a polynuclear bismuth(III) iodide complex with pentagonal bipyramidal geometry around the bismuth(III) ions. The seven coordinate bismuth(III) atom has a N2S4I-donor set consisting of one iodine atom and two chelating and bridging μ2-S,N (η2-S:η1-N) pyridine-2-thionate anions.Complexes 1–5 were evaluated for their in vitro cytotoxic activity against human adenocarcinoma cervix (HeLa) and breast (MCF-7) cancer cells. The toxicity of the complexes was studied against human fetal lung fibroblast cells (MRC-5). The influence of 1–5, upon the catalytic peroxidation of the linoleic acid by the enzyme lipoxygenase (LOX), was evaluated experimentally.

Efficient and recyclable Ru(II) arene thioamide catalysts for transfer hydrogenation of ketones: Influence of substituent on catalytic outcome

Six cationic ruthenium(II) arene thioamide complexes with the general molecular formula [Ru(η6-p-cymene)(PPh3)(L)]+ [where, L = pyridine-2-thioamide and its derivatives] have been successfully synthesized from the reaction of [Ru(η6-p-cymene)Cl2]2 with chelating thioamide ligands and PPh3 in methanol in 1:2 M ratio respectively. All the complexes were isolated as their BPh4−salts and were fully characterized by analytical and spectral (FT-IR, UV-Vis and1H-NMR) methods. The solid-state structure of one of the complexes, [Ru(η6-p-cymene)(PPh3)(L4)]BPh4 (4) (L4 = N-(2, 4, 6-Trimethylphenyl)pyridine-2-thiocarboxamide) has been established by X-ray single crystal diffraction which indicates a pseudo-octahedral (piano-stool) coordination geometry is present in the complex. The ruthenium(II) complexes have been examined for the transfer hydrogenation of various aromatic, heterocycle and cyclic ketones. The formation of ruthenium(II) hydride is confirmed by 1H- NMR and is proposed as the catalytic intermediate in this reaction. Under the optimized conditions, these ruthenium complexes served as excellent catalyst precursors which smoothly reduce the ketones with conversion up to 100%. The influence of other variables on the transfer hydrogenation reaction such as solvent, base, temperature, time, catalyst loading and substrate scope is also reported. Furthermore, the catalyst could be easily recovered and reused at least three times without obvious loss of conversions.

Synthesis of Rhodium–Primary Thioamide Complexes and Their Desulfurization Leading to Rhodium Sulfido Cubane-Type Clusters and Nitriles

Although molecular thioamide complexes of late-transition metals have been prepared since 1979, the chemistry of primary thioamide complexes remains relatively unexplored. To shed light on this area, we have investigated synthesis, structures, and reactivities of simple rhodium organometallic complexes with a primary arenecarbothioamide ligand [Cp*RhCl2{S═C(Ar)NH2-κ1S}] (Cp* = η5-C5Me5). Intra- and intermolecular hydrogen bonding in the thioamide complexes is discussed on the basis of 1H NMR spectroscopy and X-ray analysis. When these rhodium complexes were treated with a large excess amount of Et3N, desulfurization of the thioamide ligand took place to give arenecarbonitriles (ArCN) in high GC yield and the cubane-type cluster [(Cp*Rh)4(μ3-S)4] (3) in good yield as the organometallic product. Use of a smaller amount (2.4 equiv) of Et3N followed by treatment with NaBArF4 (ArF = 3,5-(CF3)2C6H3) led to the isolation of the cationic clusters [(Cp*Rh)4(μ3-S)4](BArF4) or [(Cp*Rh)4(μ3-S)4](BArF4)2 in low yield. Reaction mechanisms of the desulfurization of the coordinated thioamides and the formation and one- or two-electron oxidation of 3 during the desulfurization are discussed.

New binuclear Pd(II) thioamide complexes for the Heck reaction of aryl bromides

The reaction of binucleating thioamide ligands (L 1–L 3) with [PdCl 2(PPh 3) 2] in 1:2 molar ratio in methanol medium afforded a series of binuclear palladium(II) complexes. The synthesized complexes were characterized by elemental analysis and 1H NMR. The molecular structure of one of the complexes was established by X-ray diffraction method. The binuclear palladium(II) thioamide complex has been shown to be an active catalyst for the Heck reaction of aryl bromides with alkenes.

Bis(tpp)copper(I) thiosemicarbazonates: unexpected chemistry revealed by X-ray diffraction

Starting from bis(triphenylphosphine)copper(I) salts and from methylpyruvate thiosemicarbazone we have planned the synthesis of several complexes. The choice has fallen on these compounds for two main reasons: first, triphenylphosphines are known to stabilize copper in its lower oxidation state and, second, tertiary phosphines seem to enhance the solubility of Cu(I) thioamide complexes. The overwhelming majority of analogous compounds present the ligand that behaves as monodentate through the sulphur atom, in agreement with the soft nature of copper(I), and the remaining fourth position occupied by a halide. We have recently demonstrated that it is the presence or absence of soft ligand competitors that influence the coordination mode of thiosemicarbazones and not the protonation of the azinic nitrogen that renders them monodentate. In the course of these studies we have met with spectral and ana ly t ica l anomal ies that have been clarified by X-ray crystallography. A few compounds contain copper clusters, others contain ligands that have partially undergone a cyclization and in two cases linear and cyclic ligands bind two copper centres in two different oxidation states.

Ethynylthioamide Complexes: Synthesis, Reactivity and an Unusual Coupling Reaction with Diethylaminopropyne

The reaction of [(CO)5Cr(THF)] with propynethioic acid amides, R-C≡C-C(=S)NMe2 (R = H, SiMe3), yields the thioamide complexes [(CO)5Cr-S=C(NMe2)C≡C-H] (1a) and [(CO)5Cr- S=C(NMe2)C≡C-SiMe3] (1b). Treatment of solutions of 1a or 1b with methyllithium generates, via deprotonation or desilylation, the lithium salt Li[(CO)5Cr-S=C(NMe2)C≡C] (2). On filtration over silica, 2 is readily reprotonated. Complex 1a is inert towards methanol, however, adds diethylamine across the C≡C bond to give the thioacrylamide complex [(CO)5Cr-S=C(NMe2)C(H)=C(H)NMe2] (3). Thiourea displaces the thioamide ligand to give [(CO)5Cr-S=C(NH2)2] (4). Complex 1a reacts with half an equivalent of diethylaminopropyne in a three-component coupling to form the homobinuclear complex [(CO)5Cr-S=C(NEt2)-C(CH3)=C(H)-C(H)=C(NMe2)-C≡C-C(NMe2)=S- Cr(CO)5] (5) in high yield. The solid state structures of complexes 1a and 5 were established by X-ray structural analyses.

Hydrogen‐Bonded Network and Layered Supramolecular Structures Assembled from ClO4− Counterions with Unprecedented Monomeric [AgL2]+ and Chain Polymeric [AgL2]nn+ Complex Cations (L = Thioamide or Thiourea‐Like Ligands)

AbstractThe complexes [Ag(etu)2]ClO4 (1) and [{Ag(py2tH)2}(ClO4)(H2O)0.5]n (2) have been obtained from the reactions of AgClO4 with the corresponding thioamide ligands (etu = imidazolidine‐2‐thione; py2tH = pyridine‐2‐thione). Complex 1, consisting of centrosymmetric monomeric [Ag(etu)2]+ cations and ClO4− counterions, constitutes the first bis[thio(mono‐ or di)amide] complex (M = Cu, Ag) known thus far to possess a linear MS2 mononuclear core. Component ions behave in the crystal structure as complementary partners, with all four N−H groups of each [Ag(etu)2]+ cation and all four oxygen atoms of each ClO4− anion involved in N−H···O−Cl hydrogen bonding associations. This leads to the assembly of a three‐dimensional supramolecular network. Complex 2, whose previously reported structure has been redetermined with higher precision, contains catena‐[Ag(py2tH)2]nn+ polymeric cations consisting of linear chains of linked Ag2(μ‐S)2 rings, with distorted tetrahedral AgS4 centres. Supramolecular association through N−H···O−Cl, N−H···O(water) and Cl−O···H−O−H···O−Cl hydrogen bonding, where all N−H groups and H2O molecules and only one or two oxygen atoms of each ClO4− anion are involved, leads to the formation of a two‐dimensional layered supramolecular structure. A correlation of some stereochemical parameters and a simple qualitative sulfur‐bridge bonding model has been developed for 2 and other related thioamide complexes containing M2(μ‐S)2 rings or M−S−M′ single bridges. For these structural units, suitable ranges of tilt and twist dihedral angles have been estimated and assigned to different bonding types. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Thermochemistry of amide and thioamide complexes of arsenic trihalides

The complexes AsX 3· nL (L  1,1,3,3-tetramethyl-2-thiourea (TMTU), thiourea (TU), N, N-dimethylthioacetamide (DMTA), thioacetamide (TA), N, N-dimethylthioformamide (DMTF), N, N-dimethylacetamide (DMA) or acetamide (A); n = 1, 3 2 or 2 for X  Cl; n = 1 or 2 for X  Br, and n = 1 for X  I) were prepared and characterized by melting point, elemental analysis, TG analysis, mass spectra and IR spectroscopy. From the enthalpies of dissolution in acetone, 10, 15, 20 or 25% aqueous ethanolamine, 10, 20 or 25% ethanolic ethanolamine, 10% diethanolamine in acetone, 10 or 20% ethanolic diethanolamine and 10 or 20% aqueous diethanolamine of the complexes, arsenic trihalides and ligands at 298.15 K, the standard enthalpies (Δ r H xxx) for the Lewis acid/base reactions were determined. From Δ H xxx, the standard enthalpies of formation of arsenic trihalides and the standard enthalpies of formation of ligands, the standard enthalpies of formation of the complexes (Δ H xxx) were calculated. The standard enthalpies of decomposition of the complexes (Δ H xxx), as well as the lattice standard enthalpies (Δ M H xxx) and the standard enthalpies of the Lewis acid/base reactions in the gaseous phase (Δ r H xxx) were calculated by means of thermochemical cycles, and the standard enthalpies of arsenic-sulphur ( D̄(As-S)) and arsenic-oxygen ( D̄(As-O)) bonds were estimated. The mean energies of these bonds range from 89 to 150 kJ mol −1in the amide complexes, and from 89 to 225 kJ mol −1 in the thioamide complexes. The thermochemical data suggested the order AsCl 3 > AsBr 3 > AsI 3 for acidity and, in general, DMTF > TA  TMTU > DMA > A > DMTA > TU for basicity. Correlations between several thermochemical parameters and between thermochemical parameters and the type of donation atom, the degree of substitution of hydrogen atoms by methyl groups in the ligands, etc., were established.

ChemInform Abstract: Cr(III) Complexes with Thioamides.

AbstractStarting with CrCl3(THF)3, the two thioamide complexes (I) and (II) are prepared by reaction in refluxing THF.

Regioselective synthesis of [1-B10H9(SH)]2–and [2-B10H9(SH)]2–: potential agents for boron–Neutron capture therapy of brain tumours

The substitution reaction of [1-B10H9(N2)]– with N,N-dimethylthioformamide and the acid-catalyzed nucleophilic substitution of [B10H10]2– with tetramethylthiourea gave [1-B10H9(SCHNMe2)]– and [2-B10H9{SC(NMe2)2}]– respectively. The basic hydrolysis of these thioamide complexes yielded the 1- and 2-isomers of [B10H9(SH)]2– respectively. Their stereochemistry was determined by 1H n.m.r. spectroscopy from the S–Me chemical shift values of their S-methyl derivatives.

Phosphinsubstituierte chelatliganden: XI. NMR-spektroskopische untersuchungen ( 1H, 13C, 31P, 55Mn) an halogentricarbonylmangan-chelatkomplexen mit phosphino-thioformamid- und -thioformimidoester-liganden

A series of halotricarbonylmanganese chelate complexes, fac-(CO) 3Mn(X)L (X = Cl ( a), Br ( b), I ( c)), with thioformamide (L = Ph 2PC(S)NRMe; R = H ( 1), Me ( 2), Ph ( 3)) and the isomeric thioformimidoester (L = Ph 2PC(NR)SMe; R = Me ( 4), Ph ( 5)) ligands were prepared by thermal CO substitution of the pentacarbonylmanganese halides. The IR and NMR data indicate P,S-coordination of the ambidentate ligands and uniform Z configuration in 3–5. Due to the large linewidth of the NMR signals, the 4 J(PH) and 3 J(PC) coupling constants could not be determined for the thioamide complexes 1–3. Coordination of the thioimide 4 causes an increase in 4 J(PH) whereas 3 J(PC) remains unchanged. δ( 31P) shows a downfield coordination shift as usual for manganese complexes. The broad 55Mn NMR signals cover a range of +90 to −730 ppm (rel. KMnO 4) with the imidoester complexes 4 and 5 at the low-field side. The normal halogen dependence Cl < Br < I is observed for 55Mn shielding.

Studies on thioamido-platinum complexes: Stabilization of platinum in its higher oxidation state

The reducing power of thioamides and related compounds being often rationalised in terms of a thiol structure for the thioamido-form, it would be expected thatN-disubstituted thioamides should be able to complex platinum in its higher oxidation state. The platinum(IV) complexes of dimethylthioformamide (dmtf) and tetramethylthiourea (tmtu) are described and characterised by x.p.s. and n.m.r. spectroscopy. This paper also reports some findings concerning class II mixed-valence (PtII/PtIV) thioamide complexes.

The formation of thioamide complexes of manganese, molybdenum and rhodium from organosilicon and organotin intermediates

The interaction of N-trimethylsilylthioacetanilide and N-phenyl- S-trimethyl- tinthioacetimidate, with carbonyl halides of molybdenum, manganese and rhodium afforded a range of N-phenylthioacetamido metal carbonyl complexes in which the group behaves as a chelating ligand, and also in two different ways as a bridging group in binuclear products.