Thioamide Ligands Research Articles

Cleavable Ligands Enable Uniform Close Packing in Colloidal Quantum Dot Solids.

Uniform close packing in colloidal quantum dot solids is critical for high-optical density, high-mobility optoelectronic devices. A hybrid-ligand strategy is developed, combining the advantages of solid state and solution-phase ligand exchanges. This strategy uses a medium length thioamide ligand that is readily cleaved in a single chemical treatment, leading to quantum dot solids with uniformly packed domains 3 times larger than those observed in ligand-exchanged films.

Structural Elucidation and Antibacterial Studies on Half-Sandwich Ruthenium(II) Complexes Incorporating Arene, Phosphine, Arsine and Thioamide Ligands

Structural Elucidation and Antibacterial Studies on Half-Sandwich Ruthenium(II) Complexes Incorporating Arene, Phosphine, Arsine and Thioamide Ligands

Direct Synthesis of Cuprum(II) Complex Compounds Based on Thioamide Ligands

Complex compounds based on arylamides of benzimidazol-2-thiocarboxylic acid of the general formula (Cu(HL)Cl2)2 have been synthesized via direct method. Their physico-chemical properties have been investigated.

Secondary Thioamides as Multidentate Ligands for Functional Metal Complexes

Abstract This highlight review describes recent progress in thioamide-based transition-metal complexes, including their preparation methods and functionalities. In particular, pincer organometallics with secondary thioamide ligands are unique tools that can be used for applications in various areas such as chemical-sensor materials, tunable redox-potential complexes, polymer hybrid-luminescence materials, building blocks for multinuclear complexes, and catalysts for cross-coupling reactions.

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.

Experimental charge density studies of silver (I) complex

The antimicrobial [1] as well as antitumor activity of silver(I) complexes has been attributed to their interactions with nucleic acids, in the latter case preferentially with the bases rather than the phosphate groups [2]. The ability of silver(I) complexes to adopt structural diverse geometries with variable nuclearities , on the other hand, makes the study of silver(I) chemistry very attractive [1]. In the course of our studies of silver complexes with thioamide ligands we have determined the experimental charge density distribution in new silver(I) bromide complex with 2-mercaptobenzothiazole (mbztH) and triphenylphosphine (tpp) [AgBr(tpp)2(mbztH)], which allowed us to study e.g. the transfer of electron density to the bonding regions and the detailed analysis of different intra- and intermolecular interactions. In view of strong anticancer activity for MCF-7 (IC50 1.7510.25 μM) [3] of (1) and its sulfur containing ligand, this structure can be very interesting. Moreover the structure of (1) contains two independent complex molecules in asymmetric part of the unit cell, which together with the charge density description of mbztH and tpp allowed us to study different transferability approaches.

Modular Hydroxyamide and Thioamide Pyranoside‐Based Ligand Library from the Sugar Pool: New Class of Ligands for Asymmetric Transfer Hydrogenation of Ketones

AbstractA large library of pyranoside‐based hydroxyamide and thioamide ligands has been synthesized for asymmetric transfer hydrogenation in an attempt to expand the scope of the substrates to cover a broader range of challenging heteroaromatic and aryl/fluoroalkyl ketones. These ligands have the advantage that they are prepared from commercial D‐glucose, D‐glucosamine and α‐amino acids, inexpensive natural chiral feedstocks. By carefully selecting the ligand components (substituents/configurations at the amide/thioamide moiety, the position of amide/thioamide group and the configuration at C‐2), we found that pyranoside‐based thioamide ligands provided excellent enantioselectivities (in the best cases, ees of >99% were achieved) in a broad range of ketones, including the less studied heteroaromatics and challenging aryl/fluoroalkyls. Note that both enantiomers of the reduction products can be obtained with excellent enantioselectivities by simply changing the absolute configuration of the thioamide substituent.magnified image

ChemInform Abstract: Second‐Generation Amino Acid Furanoside Based Ligands from D‐Glucose for the Asymmetric Transfer Hydrogenation of Ketones.

A novel series of modular amino acid thioamide ligands functionalized with carbohydrates were introduced and employed in the rhodium-catalyzed asymmetric transfer hydrogenation (ATH) of aryl alkyl ...

Second‐Generation Amino Acid Furanoside Based Ligands from D‐Glucose for the Asymmetric Transfer Hydrogenation of Ketones

AbstractA novel series of modular amino acid thioamide ligands functionalized with carbohydrates were introduced and employed in the rhodium‐catalyzed asymmetric transfer hydrogenation (ATH) of aryl alkyl ketones, including the less‐studied heteroaromatic ketones. The ligands are based on amino acid hydroxyamides (pseudodipeptides), which are the most successful ligands previously used in asymmetric hydrogen transfer reactions. High enantioselectivities [up to 99 % enantiomeric excess (ee)] were achieved in the ATH of a wide range of aryl alkyl ketones by using catalysts generated in situ from [RhCl2Cp*]2 (Cp*=C5Me5) and thioamide ligands comprising a 3‐benzyl glucofuranoside backbone and a bulky isopropyl group in the α‐amino acid moiety. Interestingly, both enantiomers of the alcohol products can readily be obtained with high enantioselectivity by simply changing the absolute configuration of the α‐amino acid. The good performance can be extended to a very challenging class of industrially interesting heteroaromatic ketones (up to 99 % ee).

Ruthenium(II) half-sandwich complexes containing thioamides: Synthesis, structures and catalytic transfer hydrogenation of ketones

A new family of cationic half-sandwich complexes of the type [(η6-cymene)Ru(PPh3)(L)]+ (L = bidentate monoanionic thioamide) have been synthesized and isolated as their tetraphenylborate salts. All the synthesized ruthenium(II) arene complexes are air stable and are fully characterized by elemental analysis, spectral and X-ray diffraction methods. In chloroform solution all the complexes exhibit characteristic metal to ligand charge transfer (MLCT) absorptions and ligand based transitions. Molecular structure of the complexes 2, 3 and 4 has been determined by single crystal X-ray crystallography indicates that the thioamide ligands are coordinated to ruthenium as a bidentate O, S donor and a typical piano stool geometry was observed around ruthenium(II) metal center. Complexes 1–5 were tested as catalysts in the transfer hydrogenation of aliphatic and aromatic ketones to secondary alcohols in the presence of 2-propanol/KOH. Further, the influence of base, reaction temperature and catalyst loading in this reaction was also evaluated to find out the most active catalyst.

Modular Furanoside Pseudodipeptides and Thioamides, Readily Available Ligand Libraries for Metal‐Catalyzed Transfer Hydrogenation Reactions: Scope and Limitations

AbstractTwo new highly modular carbohydrate‐based, pseudodipeptide and thioamide ligand libraries have been synthesized for the rhodium‐ and ruthenium‐catalyzed asymmetric transfer hydrogenation (ATH) of prochiral ketones. These series of ligands can be prepared efficiently from easily accessible D‐xylose and D‐glucose. The ligand libraries contain two main ligand structures (pseudodipeptide and thioamide) that have been designed by making systematic modifications to one of the most successful ligand families developed for the ATH. As well as studying the effect of these two ligand structures on the catalytic performance, we also evaluated the effect of modifying several of the ligand parameters. We found that the effectiveness of the ligands at transferring the chiral information in the product can be tuned by correctly choosing the ligand components (ligand structure and ligand parameters). Excellent enantioselectivities (ees up to 99%) were therefore obtained in both enantiomers of the alcohol products using a wide range of substrates.

Luminescent silver nitrate complexes of bis[2-(diphenylphosphano)phenyl]ether (DPEphos): Crystal structure of [Ag(DPEphos)(py2SH) 2]NO 3

Heteroleptic silver(I) nitrate complexes containing the bis[2-(diphenylphosphano)phenyl]ether (DPEphos) ligand and the heterocyclic thioamides pyridine-2(1H)-thione (py2SH), pyrimidine-2(1H)-thione (pymtH), 4,6-dimethylpyrimidine-2(1H)-thione (dmpymtH), 1,4,5,6-tetrahydropyrimidine-2-thione (thpymtH) or 1,3-imidazolidine-2-thione (imtH 2) have been synthesized and characterized by IR and UV–Vis spectroscopy, elemental analyses and melting point determinations. The complexes can be obtained by the addition of the thioamide ligand to an AgNO 3–diphosphane adduct in dichloromethane/ethanol solution. The molecular structure of [Ag(DPEphos)(py2SH) 2]NO 3 complex has been established by single-crystal X-ray diffraction. The structure features a tetrahedral silver(I) center with two phosphorus atoms from the chelating diphos ligand, and the exocyclic sulfur atom of two heterocyclic thioamide units. Intense blue-green emission is observed in the region 470–483 nm for all the complexes in the solid state and in solution at ambient temperature.

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.

ChemInform Abstract: Asymmetric Transfer Hydrogenation of Ketones Catalyzed by Rhodium Complexes Containing Amino Acid Triazole Ligands.

AbstractNovel L‐amino acid thioamide ligands functionalized with 1,2,3‐triazoles are prepared and used as active and selective catalysts for asymmetric reduction of ketones.

Dichloridobis(N,N′-diethylthiourea-κS)mercury(II)

There are two mol­ecules in the asymmetric unit of the title compound, [HgCl2(C5H12N2S)2]. In both mol­ecules, the N,N′-diethyl­thio­urea ligands exhibit a cis,trans geometry around their C—N amide bonds. The shapes of the mol­ecules are, to a large extent, determined by intra­molecular N—H⋯Cl hydrogen bonds formed by the N—H groups from the cis amide groups. In one mol­ecule, these groups are involved in three-center hydrogen bonds involving both chloride ligands, whereas in the other mol­ecule only one Cl ligand takes part in intra­molecular hydrogen bonding. The coordination around the Hg atom is distorted tetra­hedral with an S2Cl2 donor set. Inter­molecular hydrogen bonds between N—H groups from the trans amide units of the thio­amide ligands and the chloride ligands connect the mol­ecules into a polymeric chain extending along the c axis. One of the ethyl groups of the N,N′-diethyl­thio­urea ligands is disordered over two positions in one of the mol­ecules, with an occupancy of 0.654 (17) for the major component.

Asymmetric transfer hydrogenation of ketones catalyzed by rhodium complexes containing amino acid triazole ligands

Active and selective catalysts for the asymmetric reduction of ketones, under transfer hydrogenation conditions, were obtained by combining [RhCl(2)Cp*](2), with a series of l-amino acid thioamide ligands functionalized with 1,2,3-triazoles. The obtained secondary alcohol products were formed with up to 93% ee.

Structural Motifs and Biological Studies of New Antimony(III) Iodide Complexes with Thiones

Eight new antimony(III) iodide complexes of the heterocyclic thioamides, 2-mercapto-1-methylimidazole (MMI), 2-mercaptobenzimidazole (MBZIM), 5-ethoxy-2-mercaptobenzimidazole (EtMBZIM), 2-mercaptothiazolidine (MTZD), 3-methyl-2-mercaptobenzothiazole (NMeMBZT), 2-mercapto-3,4,5,6-tetrahydropyrimidine (tHPMT), 2-mercaptopyridine (PYT), and 2-mercaptopyrimidine (PMT) of formulas {[SbI(3)(MMI)(2)].MeOH} (1), [SbI(3)(MBZIM)(2)] (2), {[SbI(2)(mu(2)-I)(EtMBZIM)(2)](2).H(2)O} (3), [SbI(3)(MTZD)] (4), [(NMeMBZT)SbI(2)(mu(2)-I)(2)(mu(2)-S-NMeMBZT)SbI(2) (NMeMBZT)] (5), {[SbI(3)(tHPMT)(3)].MeOH} (6), [SbI(3)(PYT)] (7), and [SbI(3)(PMT)(2)] (8), have been synthesized and characterized by elemental analysis, FT-IR spectroscopy, FT-Raman spectroscopy, and TG-DTA analysis. The crystal structures of 3, 4, 5, 6, and 7 were also determined by X-ray diffraction. The complexes show interesting structural motifs. Complex 6 is a monomer, with octahedral (Oh) geometry around the metal ion formed by three sulfur and three iodide atoms. Complexes 3 and 5 are dimers, with a square pyramidal (SP) geometry in each monomeric unit, while complexes 4 and 7 are polymers with pseudotrigonal bipyramidal (psi-TBP). Two or three sulfur atoms from thioamide ligands and three iodide atoms are bound to Sb atoms forming building blocks for the dimers and polymers. Strong intramolecular interactions between mu(2)-I and/or mu(2)-S and Sb atoms stabilize both structures. In dimer complex 5, two terminal iodide and one terminal sulfur atom are bonded to the Sb ion, while two mu(2)-I and one mu(2)-S bridging atoms bridge the metal ions forming psi-Oh geometry. Computational studies using multivariant linear regression (MLR) and artificial neural networks (ANN) and considering biological results (50% inhibitory concentration, IC(50)) as dependent variables derived a theoretical equation for IC(50) values of the complexes studied. The calculated IC(50) values are compared satisfactorily with the experimental inhibitory activity of the complexes measured. Complexes 3-7 were used to study their influence upon the catalytic peroxidation of linoleic acid by the enzyme Lipoxygenase (LOX). Compounds 1-8 were also tested for in vitro cytotoxicity, and they showed mostly a moderate cytostatic activity against a variety of tumor cell lines but comparable with those found for the antimony(III) chloride and bromide complexes, reported earlier [Ozturk et al. Inorg. Chem. 2007, 46, 2861-2866; Ozturk et al. Inorg. Chem. 2009, 48, 2233-2245].

Fine-tuning catalytic activity and selectivity—[Rh(amino acid thioamide)] complexes for efficient ketone reduction

Amino acid-derived thioamides are prepared and evaluated as ligands in the rhodium-catalyzed asymmetric transfer hydrogenation of ketones in 2-propanol. It is found that increasing the steric bulk at the C-terminus of the ligand had a positive impact on both activity and selectivity in the reduction reaction. In order to find the optimum catalyst, a study is performed on a series of thioamide ligands having substituents of varying size.

New Antimony(III) Bromide Complexes with Thioamides: Synthesis, Characterization, and Cytostatic Properties

New antimony(III) bromide complexes with the heterocyclic thioamides, thiourea (TU), 2-mercapto-1-methylimidazole (MMI), 2-mercapto-benzimidazole (MBZIM), 2-mercapto-5-methyl-benzimidazole (MMBZIM), 5-ethoxy-2-mercapto-benzimidazole (EtMBZIM), 2-mercapto-3,4,5,6-tetrahydro-pyrimidine (tHPMT), 2-mercaptopyridine (PYT), 2-mercapto-thiazolidine (MTZD), 3-methyl-2-mercaptobenzothiazole (MMBZT), and 2-mercaptopyrimidine (PMTH) of formulas [SbBr(3)(TU)(2)] (1), [SbBr(3)(MMI)(2)] (2), {[SbBr(2)(MBZIM)(4)](+) [Br](-) H(2)O} (3), {[SbBr(2)(mu(2)-Br)(MMBZIM)(2)](2)} (4), {[SbBr(2)(mu(2)-Br)(EtMBZIM)(2)](2) MeOH} (5), {[SbBr(3)(mu(2)-S-tHPMT)(tHPMT)](n)} (6), {[SbBr(2)(mu(2)-Br)(PYT)(2))(n)} (7), {[SbBr(2)(mu(2)-Br)(MTZD)(2)](n)} (8), [SbBr(3)(MMBZT)(2)] (9), and {[SbBr(5)](2-)[(PMTH(2)(+))(2)]} (10) have been synthesized and characterized by elemental analysis, conductivity measurements, FTIR spectroscopy, FT-Raman spectroscopy, TG-DTA analysis, and X-ray powder diffraction. The crystal structures of 3, 4, 5, 6, 7, 8, and 10 were also determined by X-ray diffraction. In 3, four sulfur atoms from thione ligands and two bromide ions form an octahedral (O(h)) cationic [SbS(4)Br(2)](+) species in which the two bromide anions lie at axial positions. A third bromide counteranion neutralizes the whole complex. 4 and 5 are dimers, whereas 6, 7 and 8 are polymers, built up by monomeric units of square pyramidal (SP) geometry around the metal center, which were formed by two sulfur atoms of thioamide ligands and three bromide ions. Finally, 10 is ionic salt containing 1D polymeric network of {[SbBr(5)](2-)}(n) anions and (-)[(PMTH(2)(+))2] counter cations in the lattice. The complexes showed mostly a moderate cytostatic activity against a variety of tumor cell lines.

Competitive bulk liquid membrane transport of some metal ions using RC(S)NHP(S)(OiPr)2 as ionophores. Unusual supramolecular “honeycomb” aggregate of the polynuclear copper(I) complex of H2NC(S)NHP(S)(OiPr)2

Competitive transport experiments involving metal ions from an aqueous source phase through a chloroform membrane into an aqueous receiving phase have been carried out using a series of N-(thio)phosphorylated (thio)amide and thiourea ligands as ionophores in the organic phase. The source phase contained equimolar concentrations of Co(II), Ni(II), Cu(II), Zn(II), Ag(I), Cd(II) and Pb(II) with the source and receiving phases being buffered at different pH. Good transport properties were observed for Ag(I) in the case of (13). The best extraction properties have been shown by (3)L(1), (3)L(8), (2)L(7), (3)L(9) and (3)L(11) which contain an unsubstituted nitrogen atom at the C[double bond, length as m-dash]S groups ((3)L(1) and (3)L(9)), or a third nitrogen atom, capable of participating in additional coordination ((3)L(8), (2)L(7) and (3)L(11)). Reaction of Cu(NO(3))(2).6H(2)O with the potassium salt of the N-thiophosphorylated thiourea NH(2)C(S)NHP(S)(OiPr)(2) formed a new supramolecular Cu(I) complex, [{Cu(6)((2)L(1))(6)}{Cu(3)((2)L(1))(3)}.4Me(2)CO] that contains both trinuclear and hexanuclear forms in its solid state structure, and in solution.