Sulfoxide Ligands Research Articles

Iodine-mediated substitution of terminal ligands in [{M6I8}I6]2– (M = Mo, W) by DMSO

The family of octahedral iodide cluster complexes of molybdenum and tungsten – [{M6I8}L6]n – exhibit a unique set of properties with significant practical potential. Due to the strong influence of terminal ligands L on these properties, the search for new simpler, more convenient and cheaper approaches for their substitution is an urgent task. This work demonstrates a new one-step method for terminal ligand substitution using well-known and readily available complexes [{M6I8}I6]2–. The synthetic technique involves the addition of molecular iodine to the reaction mixture in order to bind the released I– ions, thereby facilitating the reaction process. As a result, two new cluster complexes with dimethyl sulfoxide ligands [{M6I8}(DMSO)6](I3)4 (M = Mo (1), W (2)) have been obtained and structurally characterized. The optical properties of the obtained compounds have been studied both in solid state and in solution, and Eg values have been calculated from the solid-state absorption spectra. The presence of I3– anions has been shown to quench the emission of the cluster complexes, explaining the absence of luminescence in the obtained compounds.

Cis,cis,cis-Di-chlorido-bis-(N4,N4-di-methyl-pyridin-4-amine-κN1)bis-(dimethyl sulfoxide-κS)ruthenium(II).

The structure of the title compound, [RuCl2(C7H10N2)2(C2H6OS)2], has monoclinic (P21/n) symmetry. The Ru-N distances of the coordination compound are influenced by the trans chloride or di-methyl-sulfoxide-κS ligands. The mol-ecular structure exhibits disorder for two of the terminal methyl groups of a dimethyl sulfoxide ligand.

Synthesis, spectroscopic characterization, crystal structure and DNA docking studies of a new trans-platinum saccharinate complex containing aqua and dimethyl sulfoxide ligands

A new trans-platinum complex, trans-[Pt(sac)2(H2O)(DMSO)] (sac= saccharinate; DMSO= dimethyl sulfoxide), was synthesized and characterized by elemental analysis, UV, FTIR, NMR spectroscopy and X-ray single-crystal diffraction. In the mononuclear complex, the platinum(II) cation was coordinated by two N-coordinated sac ligands in the trans position, the sulfur atom of the DMSO ligand, and an aqua ligand, forming a distorted square planar coordination geometry. The interaction of the platinum(II) complex with DNA was studied using molecular docking. The complex successively docked into the minor groove of DNA via intermolecular hydrogen bonds with the adenine, cytosine, and guanine bases.

Effect of Tethered Sulfur Ligands on the Association Constants of Dirhodium(II,II) Paddlewheel Complexes

AbstractHerein we report on the association constants (Ka) of dirhodium(II,II) complexes bearing tethered thioether or sulfoxide ligands in the presence of binding analytes. The effect of substituent and tether length modifications on Ka and the stability of the complexes were analyzed by UV‐vis using pyridine and cysteine as binding analytes of interest. When pyridine was the incoming exogenous species, dirhodium(II,II) complexes with tethered sulfur ligands reduced the axial coordination of pyridine by up to four‐fold when compared to dirhodium(II,II) complexes without tethered axial coordination. Tuning the tethered sulfur coordination through changes in tether length, substituent, and electronics resulted in Ka values that spanned 2.6×103 M−1 to 8.1×103 M−1. The differences in Ka were correlated with structural features of crystals obtained from single crystal X‐ray diffraction and results pointed to release of strain as a factor in the association constants. Interestingly, cysteine interactions were greater for complexes with tethered, axial ligands than those without, alluding to an alternate mode of coordination with cysteine. These results demonstrate the tunability of tethered, axial coordination on dirhodium(II,II) paddlewheel complexes and provide access to controlled binding of exogenous species.

Ligand Sulfur Oxidation State Progressively Alters Galectin-3-Ligand Complex Conformations To Induce Affinity-Influencing Hydrogen Bonds.

Galectins play biological roles in immune regulation and tumor progression. Ligands with high affinity for the shallow, hydrophilic galectin-3 ligand binding site rely primarily on a galactose core with appended aryltriazole moieties, making hydrophobic interactions and π-stacking. We designed and synthesized phenyl sulfone, sulfoxide, and sulfide-triazolyl thiogalactoside derivatives to create affinity-enhancing hydrogen bonds, hydrophobic and π-interactions. Crystal structures and thermodynamic analyses revealed that the sulfoxide and sulfone ligands form hydrogen bonds while retaining π-interactions, resulting in improved affinities and unique binding poses. The sulfoxide, bearing one hydrogen bond acceptor, leads to an affinity decrease compared to the sulfide, whereas the corresponding sulfone forms three hydrogen bonds, two directly with Asn and Arg side chains and one water-mediated to an Asp side chain, respectively, which alters the complex structure and increases affinity. These findings highlight that the sulfur oxidation state influences both the interaction thermodynamics and structure.

Examining the adsorption of gases into solid crystalline molecular copper(II) 3,5-bis(trifluoromethyl)benzoate derivatives

Two copper(II) complexes, both involving the anionic 3,5-bis(trifluoromethyl)benzoate ligand (TFMBz), have been prepared and their structure elucidated by single crystal-X ray diffraction. [Cu(TFMBz)2(ISNA)2] (1) is a mononuclear complex, in which the sphere of coordination of Cu(II) is completed by two neutral isonicotinamide (ISNA) auxiliary ligands. Hydrogen bonding formed between auxiliary ISNA ligands determines the formation of a 2D supramolecular network. [Cu2(TFMBz)4(DMSO)2] (2) is a binuclear complex, in which the four carboxylate ligands define the typical paddle wheel structure often found in copper complexes, containing also the ancillary dimethyl sulfoxide (DMSO) ligand in axial positions. The elucidated crystallographic data provide the static view of the crystal structures, which reveals only non-interconnected voids for both materials. Even that, compound 1 shows an appreciable adsorption of CO2 at 273 K (ca. 1 CO2 molecule/Cu atom at 100 kPa), concomitant with a reduced adsorption of Ar or N2 under similar conditions, which implies a considerable degree of selectivity for CO2. Moreover, 1 does not adsorb N2 or Ar at 77 K and 100 kPa. This behavior suggests that the stablished intermolecular hydrogen bonds rest flexibility and dynamism to 1 at low temperature. Contrarily, increasing the temperature transient porosity is originated, which allows guest molecules to diffuse through the cavities. Compound 2 shows adsorption of N2 and Ar at 77 K, indicating that vibrations in the network and rotation of some CF3 groups, necessary to favor adsorbate diffusion, are still feasible at this low temperature.

Recent Advances for Chiral Sulfoxides in Asymmetric Catalysis

AbstractChiral sulfoxide is considered to be an ideal candidate ligand for transition-metal-catalyzed asymmetric reactions due to its ease of synthesis, stability, and exceptional S-stereological orientation control. This paper reviews the different types of asymmetrical reactions with chiral sulfoxide ligands in recent years, as well as a discussion of efficient methods for the preparation of some enantiomerically pure sulfoxides.1 Introduction2 Chiral Sulfoxides as Ligands in Metal-Catalyzed Asymmetric Catalysis3 Synthesis of Chiral Sulfoxides4 Conclusions

Ruthenium-Locked Helical Chirality: A Barrier of Inversion and Formation of an Asymmetric Macrocycle.

Upon coordination to metal centers, tetradentate ligands based on the 6,6′-bis(2″-aminopyridyl)-2,2′-bipyridine (bapbpy) structure form helical chiral complexes due to the steric clash between the terminal pyridines of the ligand. For octahedral ruthenium(II) complexes, the two additional axial ligands bound to the metal center, when different, generate diastereotopic aromatic protons that can be distinguished by NMR. Based on these geometrical features, the inversion barrier of helical [RuII(L)(RR′SO)Cl]+ complexes, where L is a sterically hindered bapbpy derivative and RR′SO is a chiral or achiral sulfoxide ligand, was studied by variable-temperature 1H NMR. The coalescence energies for the inversion of the helical chirality of [Ru(bapbpy)(DMSO)(Cl)]Cl and [Ru(bapbpy)(MTSO)(Cl)]Cl (where MTSO is (R)-methyl p-tolylsulfoxide) were found to be 43 and 44 kJ/mol, respectively. By contrast, in [Ru(biqbpy)(DMSO)(Cl)]Cl (biqbpy = 6,6′-bis(aminoquinolyl)-2,2′-bipyridine), increased strain caused by the larger terminal quinoline groups resulted in a coalescence temperature higher than 376 K, which pointed to an absence of helical chirality inversion at room temperature. Further increasing the steric strain by introducing methoxy groups ortho to the nitrogen atoms of the terminal pyridyl groups in bapbpy resulted in the serendipitous discovery of a ring-closing reaction that took place upon trying to make [Ru(OMe-bapbpy)(DMSO)Cl]+ (OMe-bapbpy = 6,6′-bis(6-methoxy-aminopyridyl)-2,2′-bipyridine). This reaction generated, in excellent yields, a chiral complex [Ru(L″)(DMSO)Cl]Cl, where L″ is an asymmetric tetrapyridyl macrocycle. This unexpected transformation appears to be specific to ruthenium(II) as macrocyclization did not occur upon coordination of the same ligand to palladium(II) or rhodium(III).

Synthesis of Sulfur-Stereogenic Sulfoximines via Co(III)/Chiral Carboxylic Acid-Catalyzed Enantioselective C–H Amidation

Sulfoximines bearing stereogenic sulfur atoms are ubiquitous motifs in pharmaceuticals, agricultural chemicals, and bioactive compounds. Herein, we report the synthesis of sulfur-stereogenic sulfoximines via Co(III)/chiral carboxylic acid-catalyzed enantioselective C–H amidation. A broad range of cyclic and acyclic sulfur-stereogenic sulfoximines were isolated in good yields and enantioselectivities (up to an 86% yield and 1.5:98.5 er). The acyclic amidation products can be reduced to potential N,S-chiral sulfoxide ligands, which could be further transformed into recyclable chiral auxiliaries in the Pd-catalyzed diastereoselective C(sp3)–H activation of aliphatic carboxylic acids.

Bis(catecholato-κ2 O,O')bis-(dimethyl sulfoxide-κO)titanium(IV).

Bis(benzene-1,2-diolato-κ2 O,O')bis-(dimethyl sulfoxide-κO)titanium(IV), [Ti(C6H4O2)2(C2H6OS)2], crystallizes with two crystallographically independent mol-ecules in the space group P21/c emulating ortho-rhom-bic Pbca symmetry (β = 90.0445 (9)°]. The two mol-ecules are related by pseudo-glide symmetry, broken by modulation of each one catecholate and dimethyl sulfoxide (DMSO) ligand. Twinning by pseudomerohedry was observed [twin ratio 0.5499 (7):0.4401 (7)]. Complex 3 was obtained by heating of diprotonated titanium tris-catecholate precursor 2H in DMSO, by formal displacement of a catechol mol-ecule by two DMSO mol-ecules. Complex 3 is just the second heteroleptic, mono-nuclear, neutral bis-catecholate complex with TiO6 metal coordination, the only other one being its bis-DMF analogue 6. The two mol-ecules of 3 exhibit a distorted octa-hedral geometry. The geometry and distortions from ideal symmetry of 3 are discussed and compared to 6 and to cationic tris-catecholate titanium complexes.

Thermodynamic Resolution of Pharmaceutical Precursor Modafinil Acid on the Basis of Chiral‐at‐Metal Strategy

Main observation and conclusionChiral‐at‐metal strategy was developed to resolve the essential sulfoxide pharmaceutical intermediates R‐modafinil acid and its analogues with high yields and ee values. The efficient resolution process was achieved based on the diastereoselective discrimination caused by hydrogen bond and intramolecular π‐π interaction between chiral‐at‐metal center and the coordinated chiral sulfoxide ligands. Moreover, the chiral Ir(III) receptor can be reused with complete retention of their configurations and without the loss of reaction activity and enantioselectivity. This work provides a new access to synthesize R‐modafinil acid as well as its analogues and develops the application of chiral‐at‐metal strategy in chiral resolution.

Реакция пентафенилфосфора с гексахлороплатиновой кислотой

Tetraphenylphosphonium hexachloroplatinate (1) was synthesized by the interaction of pentaphenylphosphorus with hexachloroplatinic acid in acetone. The recrystallization of complex 1 from dimethylsulfoxide gave tetraphenylphosphonium dimethylsulfoxidopentachloroplatinate (2). The compounds have been characterized by IR-spectroscopy and X-ray analysis. The absorption bands characterizing stretching vibrations of the phenyl groups are present in the IR spectra, recorded on a Shimadzu IRAffinity-1S Fourier spectrometer in the 4000–400 cm–1 area in KBr pellets. According to the X-ray analysis, the compound unit cell parameters are: triclinic syngony, space group (1, 2), а = 10.205(10), b = 10.970(15), c = 12.160(11) Å (1), а = 7.7667(4), b = 13.3069(7), c = 14.2562(7) Å (2), a = 73,65(4)°, β = 80.64(3)°, g = 77.48° (1), a = 80.972(4)°, β = 88.205(4)°, g = 89.199(4)° (2), V = 1272(2) Å3 (1), 1454.38(13) Å3 (2). The crystals of complexes 1 and 2 consist of the tetrahedral tetraphenylphosphonium cations and octahedral anions. In cations the phosphorus atoms have a slightly distorted tetrahedral environment (the CPC angles are 107.8(3)-113.2(3)° (1), 105.9(3)–112.9(3)° (2), the P-C distance is 1.785(6)-1.805(6) Å (1), 1.783(7)–1.791(6) Å (2). Platinum atoms in the anions of complexes 1 and 2 are hexacoordinated. In complex 2 the dimethyl sulfoxide ligand is coordinated with the Pt atom via the sulfur atom 2.290(2) Å. Complete tables of coordinates of atoms, bond lengths and valence angles are deposited at the Cambridge Structural Data (CCDC 1865783, 829586 http://www.ccdc.cam.ac.uk).

Catena-Poly[barium(II)-μ2-(dimethyl sulfoxide)-κ2 O:O-bis-(μ2-2,4,6-tri-nitro-phenolato-κ4 O 2,O 1:O 1,O 6)

The asymmetric unit of the title barium coordination polymer, [Ba(C6H2N3O7)2(C2H6OS)] n , consists of a barium cation (site symmetry m) and a dimethyl sulfoxide (DMSO) ligand (point group symmetry m) and a 2,4,6-tri-nitro-phenolate anion located in general positions. The S atom and the methyl group of DMSO are disordered over two sets of sites. The DMSO ligand bridges a pair of BaII atoms resulting in a chain extending parallel to the a axis. The unique 2,4,6-tri-nitro-phenolate anion also bridges a pair of BaII ions via the phenolic oxygen atom, with each BaII being additionally bonded to an oxygen atom of an adjacent nitro group. The μ 2-monoatomic bridging binding mode of both types of ligands results in the formation of an infinite chain of face-sharing {BaO10} polyhedra flanked by the remaining parts of the 2,4,6-tri-nitro-phenolato and DMSO ligands. In the one-dimensional coordination polymer, parallel chains are inter-linked with the aid of C-H⋯O hydrogen bonds.

Oxidative Addition of Biphenylene and Chlorobenzene to a Rh(CNC) Complex.

The synthesis and organometallic chemistry of rhodium(I) complex [Rh(CNC–Me)(SOMe2)][BArF 4], featuring NHC‐based pincer and labile dimethyl sulfoxide ligands, is reported. This complex reacts with biphenylene and chlorobenzene to afford products resulting from selective C–C and C–Cl bond activation, [Rh(CNC–Me)(2,2'‐biphenyl)(OSMe2)][BArF 4] and [Rh(CNC–Me)(Ph)Cl(OSMe2)][BArF 4], respectively. A detailed DFT‐based computational analysis indicates that C–H bond oxidative addition of these substrates is kinetically competitive, but in all cases endergonic: contrasting the large thermodynamic driving force calculated for insertion of the metal into the C–C and C–Cl bonds, respectively. Under equivalent conditions the substrates are not activated by the phosphine‐based pincer complex [Rh(PNP‐iPr)(SOMe2)][BArF 4].

Easy Access to Polyfunctionalized Chiral Decalins.

An unexpected ring expansion that converts hydrindanes into decalins via an unprecedented dyotropic reaction involving a mesylate group has been observed, and this paved the way for easy access to polyfunctionalized chiral decalins. These polyfunctionalized chiral decalins can be very useful building blocks for the synthesis of the thia analogues of many natural compounds. They can also be used in asymmetric catalysis and also in the synthesis of the new analogues of vitamin D with a modified D ring and side chain. The use of chiral sulfoxide ligands for asymmetric catalysis or asymmetric sulfur ylide-mediated epoxidation of carbonyl compounds is a very important topic in the field of organic chemistry, hence our results could be useful to the scientific community.

Structure of a diorganotelluroxonium(IV) cation, {[2,6-(CH2NMe2)2C6H3Te(μ-O)]2}2+, with the tri-chlorido-(dimethyl sulfoxide)-platinum(II) anion.

In the title salt, di-μ-oxido-bis-{2,6-bis-[(di-methyl-amino)-meth-yl]phenyl-κC 1}tellurium(-IV) bis[tri-chlorido-(dimethyl sulfoxide-κS)platinate(II)], (C24H38N4O2Te2)[PdCl3(C2H6OS)]2, which crystallizes in the triclinic space group P , each Te atom is in a distorted five-coordinated TeO2N2C square-pyramidal geometry (τ values of 0.026 and 0.001) with the C atoms of the phenyl rings occupying the apical positions. The phenyl rings in the [C24H38N4O2Te2]2+ cation are in a cis arrangement to enable this species to participate in Te⋯Cl cation-anion inter-actions. There are also C-H⋯O inter-actions involving the dimethyl sulfoxide ligands and numerous cation-anion and anion-anion C-H⋯Cl inter-actions, which link the ions into a complex three-dimensional array.

SYNTHESIS AND STRUCTURE OF (METHOXYMETHYL)TRIPHENYLPHOSPHONIIUM TRICHLORO(DIMETHYLSULFOXIDO)PLATINATE

(Methoxymethyl)triphenylphosphonium trichloro(dimethylsulfoxido)platinate [Ph3PCH2OCH3][PtCl3(dmso-S)] was synthesized by the reaction of hexachloroplatinic acid with (methoxymethyl)triphenylphosphonium chloride in dimethyl sulfoxide. During the reaction, Pt (IV) was reduced to Pt (II). The reactions are accompanied by the ligand exchange in anions with substitution of the S-coordinated dimethyl sulfoxide molecule for one of chlorine atoms. Slow evaporation of the solvent led to the formation of large orange crystals. The product structure was determined by XRDA. The structures were interpreted by the direct method. Positions and temperature parameters of non-hydrogen atoms were refined in isotropic and then in anisotropic approximations by the full-matrix LSM. The X-ray diffraction pattern of crystal I was carried out on a Bruker D8 QUEST diffractometer. According to the data of X-ray analysis the unit cell crystallographic parameters of compound I are [crystal system monoclinic, space group P21/c, M 686.90, a 14.48(2), b 14.48(2), c 19.99(3) Å]. The tetrahedral configuration of the (methoxymethyl)triphenylphosphonium cation approaches the ideal values (CPC angles are 108.5(2)°-110.3(2)°, bond lengths Р-С are slightly differ from each other). Platinum atoms in anions have square coordination (trans-arranged angles ClPtCl are 177.65(5)°, SPtCl are 178.88(6)°, cis-angles approach 90°). The bond lengths Pt–Cl are equal to 2.290(3)–2.314(3) Å, Pt–S are equal to 2.205(3) Å. The platinum atoms are coordinated by three chlorine atoms and dimethyl sulfoxide molecule in the anion. Dimethyl sulfoxide molecule is coordinated to the platinum atoms by sulfur atoms. The geometry of the coordinated dimethyl sulfoxide ligand [OSC and СSC angles, S−O bond] differs from the geometry of a free dimethyl sulfoxide molecule.

Optimisation of pyruvate hyperpolarisation using SABRE by tuning the active magnetisation transfer catalyst.

Hyperpolarisation techniques such as signal amplification by reversible exchange (SABRE) can deliver NMR signals several orders of magnitude larger than those derived under Boltzmann conditions. SABRE is able to catalytically transfer latent magnetisation from para-hydrogen to a substrate in reversible exchange via temporary associations with an iridium complex. SABRE has recently been applied to the hyperpolarisation of pyruvate, a substrate often used in many in vivo MRI studies. In this work, we seek to optimise the pyruvate-13C2 signal gains delivered through SABRE by fine tuning the properties of the active polarisation transfer catalyst. We present a detailed study of the effects of varying the carbene and sulfoxide ligands on the formation and behaviour of the active [Ir(H)2(η2-pyruvate)(sulfoxide)(NHC)] catalyst to produce a rationale for achieving high pyruvate signal gains in a cheap and refreshable manner. This optimisation approach allows us to achieve signal enhancements of 2140 and 2125-fold for the 1-13C and 2-13C sites respectively of sodium pyruvate-1,2-[13C2].

Syntheses and Characterization of a Pair of Isomers of Heteroleptic Bis(Bidentate) Ruthenium(II) Complexes with Two Different Monodentate Ligands.

Two isomers of heteroleptic bis(bidentate) ruthenium(II) complexes with dimethyl sulfoxide (dmso) and chloride ligands, trans(Cl,Nbpy )- and trans(Cl,NHdpa )-[Ru(bpy)Cl(dmso-S)(Hdpa)]+ (bpy: 2,2'-bipyridine; Hdpa: di-2-pyridylamine), are synthesized. This is the first report on the selective synthesis of a pair of isomers of cis-[Ru(L)(L')XY]n+ (L≠L': bidentate ligands; X≠Y: monodentate ligands). The structures of the ruthenium(II) complexes are clarified by means of X-ray crystallography, and the signals in the 1 H NMR spectra are assigned based on 1 H-1 H COSY spectra. The colors of the two isomers are clearly different in both the solid state and solution: the trans(Cl,Nbpy ) isomer has a deep red color, whereas the trans(Cl,NHdpa ) isomer is yellow. Although both complexes have intense absorption bands at λ≈440-450 nm, only the trans(Cl,Nbpy ) isomer has a shoulder band at λ≈550 nm. DFT calculations indicate that the LUMOs of both isomers are the π* orbitals in the bpy ligand, and that the LUMO level of the trans(Cl,Nbpy ) isomer is lower than that of the trans(Cl,NHdpa ) isomer due to the trans effect of the Cl ligand; thus resulting in the appearance of the shoulder band. The HOMO levels are almost the same in both isomers. The energy levels are experimentally supported by cyclic voltammograms, in which these isomers have different reduction potentials and similar oxidation potentials.

Thermodynamic Resolution and Enantioselective Synthesis of C2-Symmetric Bis-sulfoxides Based on Chiral Iridium(III) Complexes.

Enantiopure Λ-[Ir(dfppy)2(MeCN)2](PF6) and Δ-[Ir(dfppy)2(MeCN)2](PF6) (where dfppy is (4,6-difluoropheny)pyridine) were demonstrated to preferentially react with (S,S)-1,2-bis(arylsulfinyl)ethane and (R,R)-1,2-bis(arylsulfinyl)ethane, respectively, under thermodynamic equilibrium. Sequential treatment of Λ-[Ir(dfppy)2(MeCN)2](PF6) and Δ-[Ir(dfppy)2(MeCN)2](PF6) with C2-symmetric bis-sulfoxides led to diastereoselective formation of the corresponding diastereomers Λ-[Ir(dfppy)2(R,R)-bis-sulfoxide)](PF6) in 90-92% and Δ-[Ir(dfppy)2(S,S)-bis-sulfoxide)](PF6) in 88-90%, respectively. The uncoordinated (R,S)-bis-sulfoxides were afforded in 45% with >97% de values. Enantiopure (S,S)-bis-sulfoxides and (R,R)-bis-sulfoxides were respectively obtained by the release of sulfoxide ligands from the corresponding complexes in the presence of glycine in yields of 20-21% with 97-99% ee values. The enantioreceptors Λ-[Ir(dfppy)2(MeCN)2](PF6) and Δ-[Ir(dfppy)2(MeCN)2](PF6) can be recycled and reused in the next reaction cycle. Moreover, a protocol for asymmetric oxidation of prochiral bis-sulfide into enantiopure C2 symmetric bis-sulfoxide was also developed in a high enantioselectivity. The absolute configurations at the metal centers and sulfur atoms were determined by X-ray crystallography.