Selenium Ligands Research Articles

Systematics of stable copper and silver clusters protected by small bite chelating bidentate sulfur and selenium ligands related to their polyhedral cavities: analogies to aliphatic compounds and three-dimensional spherical aromatic systems.

Silver and copper clusters capped by external chelating dithiolate ligands can be classified according to the cavities in their central coinage metal polyhedra. Silver clusters composed exclusively of fused tetrahedra are analogous to simple saturated organic compounds. The only interstitial atom that can be fit into an Ag4 tetrahedron is hydrogen. Silver polyhedra with larger trigonal prismatic or cubic cavities, including highly distorted cubic cavities, can accommodate halide and chalcogenide anions. The still larger 12-vertex icosahedral and cuboctahedral coinage metal cavities can accommodate oxoanions of the types SO32- and SO42- and their heavier congeners or alternatively interstitial coinage or platinum group metals leading to central M'@M12 units. Copper clusters with central cuboctahedra and silver clusters with central icosahedra possessing interstitial metal atoms approximate sphericality and provide examples of electron-rich metal superatoms with an average metal oxidation state of less than +1. Such copper cluster superatoms have two extra electrons corresponding to a filled 1S2 superatomic orbital. The silver cluster superatoms are electron richer with eight extra electrons corresponding to filled 1S2 + 1P6 superatomic orbitals. In these silver clusters seven or eight faces of the central Ag12 icosahedron are capped by additional silver atoms in order to provide these additional electrons.

Hydrolysis of phosphate diester catalyzed by new mononuclear copper(II) complexes containing selenium ligands

AbstractThree new copper(II) mononuclear complexes containing different organoselenium groups (1–3) were synthesized and characterized by the following techniques: elemental analysis, IR and UV‐Vis spectroscopies, electrochemical and conductimetric analysis, and mass spectrometry. Three new complexes, with substituents made in the para position of the aromatic portion of the N,N‐bis(2‐(phenylselanyl)ethyl)amine ligand: p‐OCH3 (1), p‐CH3 (2), and p‐Cl (3), were synthetized to compare with the already published complex (4), with no substituents. The ligand coordinates to the copper(II) center in a tridentate way with Se, N, Se as donor atoms. The hydrolytic activity in phosphate diester cleavage of the complexes was investigated using 2,4‐BDNPP as substrate. The modifications in the ligand are reflected in the difference between the catalytic and activation parameters, where the kcat values follow the order: 4 > 2 > 3 > 1.

Copper selenide sensitized low-cost porous coordination polymers towards efficient capture trace gaseous elemental mercury

Mercury, as a highly toxic atmospheric pollutant, poses serious hazards to global health and ecosystems. Developing low-cost sorbents with simultaneous fast capture rate and large uptake capacity to reduce elemental mercury (Hg0) emissions from industrial flue gas remains a formidable challenge. Herein, a rationally designed surfactant-assisted method was developed to construct copper selenide (CuSe) sensitized porous coordination polymers (CAU-10-H) as an efficient Hg remediator. The CuSe/CAU-10-H (0.8NC-CAU) exhibits superior near-100 % gaseous Hg0 removal efficiency over a wide temperature range (30–120 °C), implying its adaptability under different implementations. The equilibrium Hg0 adsorption capacity and initial Hg0 uptake rate of 0.8NC-CAU are 748.09 mg·g−1 and 63.21 μg·g−1·min−1, respectively, surpassing that of conventional sorbents and comparable to the benchmark materials. Furthermore, 0.8NC-CAU can adapt to harsh conditions with different flue gas impurities containing SO2, NO, and H2O to maintain high selectivity and stability, which is advantageous for real-world applications. Density functional theory (DFT) reveals that unsaturated selenium ligands as electron acceptors are critical affinity sites for facilitating Hg0 capture, resulting in stable HgSe species. More importantly, the facile preparation, prominent uptake capacity, and rapid capture rate of the 0.8NC-CAU material make it cost-effective. This work proposes a potential trap for Hg0 capture from industrial flue gas and facilitates the development of hybrid-functionalized materials for environmental remediation.

A palladium complex of a macrocyclic selenium ligand: catalyst for the dehydroxymethylation of dihydroxy compounds.

This report describes the synthesis of a seventeen-membered macrocyclic ring containing ligand (L1) by the reaction of 1,8-bis(2-(chloromethyl)phenoxy)octane with selenium powder. The trans-palladium dichloride complex (C1) of the macrocyclic selenium ligand was synthesized from its reaction with the Pd(CH3CN)2Cl2 precursor. The formation of the ligand and complex was authenticated with the help of various analytical techniques like 1H and 13C{1H} NMR, HRMS, FTIR, UV-visible spectroscopy, and elemental analysis. The structure of the ligand and its coordination mode with the palladium precursor were authenticated with the help of single crystal X-ray diffraction. The complex possesses a distorted square planar geometry around the palladium center. The new ligand and complex are air and moisture insensitive and stable at room temperature for over three months. The variable temperature NMR data and computational studies suggest selenium inversion in the palladium complex (C1) with an inversion barrier of ∼22.6 kcal mol-1. The palladium complex C1 was used as a catalyst for the dehydroxymethylation of long alkyl chain containing dihydroxy compounds. Generally, two separate catalysts are used for dehydroxymethylation (one for the oxidation of the alcohol and the other for the decarbonylation of the aldehyde). Here a single catalyst shows the dual action of dehydroxymethylation with up to 91% yield under only 5.0 mol% catalyst loading. A broad substrate scope can be achieved with good functional group tolerance. The PPh3 and Hg poisoning tests suggest the homogeneous nature of the reaction. Interestingly, the same long alkyl chain containing dihydroxy compounds were reported to undergo macrolactonization when reacted with a ruthenium catalyst.

Bulky Selenium Ligand Stabilized Trans-Palladium Dichloride Complexes as Catalyst for Silver-Free Decarboxylative Coupling of Coumarin-3-Carboxylic Acids.

This report describes the syntheses of three new trans-palladium dichloride complexes of bulky selenium ligands. These complexes possess a Cl-Pd-Cl rotor spoke attached to a Se-Pd-Se axle. The new ligands and palladium complexes (C1-C3) were characterized with the help of NMR, HRMS, UV-Vis., IR, and elemental analysis. The single-crystal structure of metal complex C2 confirmed a square planar geometry of complex with trans-orientation. The X-ray structure revealed intramolecular secondary interactions (SeCH-Cl) between chlorine of PdCl2 and CH2 proton of selenium ligand. Variable-temperature NMR data shows coalescence of diastereotopic protons, which indicates pyramidal inversion of selenium atom at elevated temperature. The relaxed potential energy scan of C2 suggests a rotational barrier of ∼12.5 kcal/mol for rotation of chlorine atom through Cl-Pd-Cl rotor. The complex C3 possesses dual intramolecular secondary interactions (OCH2 -Cl and SeCH2 -Cl) with stator ligand. Molecular rotor C2 was found to be a most efficient catalyst for the decarboxylative Heck-coupling under mild reaction conditions. The protocol is applicable to a broad range of substrates with large functional group tolerance and low catalyst loading (2.5 mol %). The mechanism of decarboxylative Heck-coupling reaction was investigated through experimental and computational studies. Importantly the reaction works under silver-free conditions which reduces the cost of overall protocol. Further, the catalyst also worked for decarboxylative arylation and decarboxylative Suzuki-Miyaura coupling reactions with good yields of the coupled products.

Experimental and theoretical insights into thetransinfluence of organo-sulfur and -selenium ligands in 5,6-membered palladium(ii) cationic pincer complexes based on iminophosphoranes

Thetransinfluence of organochalcogen ancillary ligands was assessed by experimental and DFT studies in 5,6-membered SNS and SNSe Pd(ii) pincers.

Regioselective C-H arylation of imidazoles employing macrocyclic palladium(II) complex of organoselenium ligand

In this report we have presented synthesis of a new air stable bidentate selenium ligand (L1) by the reaction of 1,8-bis(2-(chloromethyl)phenoxy)octane with sodium salt of diphenyl diselenide. The reaction of bidentate selenium ligand (L1) with Pd(CH3CN)2Cl2 in acetonitrile under reflux conditions resulted nineteen membered ring macrocyclic palladium(II) complex. The structure of ligand precursors, ligand, and macrocyclic palladium(II) complex were authenticated by using 1H, 13C{1H} NMR spectroscopy and elemental analysis. The repeated attempts to obtain single crystals of macrocyclic palladium(II) complex were unsuccessful probably due to long flexible aliphatic chain in the molecule. The air and moisture stable, thermally robust macrocyclic palladium(II) complex was employed as catalyst to catalyze the regioselective arylation reaction of imidazole derivatives. The reaction works efficiently without any need of inert atmosphere. The current protocol works under mild reaction conditions with exclusive C-5 regioselectivity. Excellent yields (~73–95%) were obtained by using only 1.5 mol% of C1, with wide range of derivatives and large functional group tolerance. Homogeneous nature of catalysis process was confirmed with the help of mercury and triphenylphosphine poisoning tests. Further, the catalyst can be reused with significant loss (22%) in the efficiency.

Selenium ligands doped ZnS for highly efficient immobilization of elemental mercury from coal combustion flue gas

At the upstream of electrostatic precipitator (ESP) or bag house (BH), using sorbents with excellent adsorption capacity is a common method for capturing mercury (Hg) from coal-fired power plant flue gas. ZnS, an inexpensively and conveniently prepared metal sulfide, can even be collected from nature, and is a promising candidate for its sulfur resistance. In this work, selenium ligands (Se 2− and Se 0 ) were introduced into ZnS for enhancing Hg 0 capture capability. The experimental results showed that the Hg 0 removal efficiency can reach 100% in a wide temperature range from 40 ℃ to 300 ℃ when the Se ratio was 30 wt% (30SZ). Compared with pure ZnS and Se powder, Se/ZnS were all exhibited an excellent absorbent capability. A long term experiment was imposed on 30SZ, and the sample adsorption capacity remained unchanged. Moreover, O 2 and SO 2 had insignificant effects on Hg 0 adsorption, NO showed a slight competition for Hg 0 adsorption. It was found that Se ligands (Se 2− and Se 0 ) and surface active S (S 2- and S) sites immobilized Hg 0 over the Se/ZnS surface, and in turn the adsorbed Hg 0 was basically converted to HgSe and HgS, and the adsorption mechanism was also proposed. With these advantageous performances, 30SZ is expected to be an economically feasible and scientifically sound sorbent. This work also provides a promising way for Hg 0 capture from coal combustion flue gas. • Inactive synthesized ZnS were functionalized to be highly efficient mercury sorbents. • The removal efficiencies can reach 100% in a wide temperature range from 40 to 300 ℃. • Se/ZnS had higher binding energy of Hg-Se to improve the adsorption capability. • The captured mercury is mainly converted into HgSe by chemisorption. • The components in the SFG have no obvious poison effects to synthesized 30SZ.

Palladium complexes of chalcogenoethanamine (S/Se) bidentate ligands: Applications in catalytic arylation of C[sbnd]H and O[sbnd]H bonds

This report describes the syntheses of N,E (E = S, Se) coordinated bidentate palladium complexes, by the reaction of N-(2-bromobenzyl)-2-(phenylthio/selanyl)ethanamine (3, 4) with [PdCl2(CH3CN)2]. The new ligands and palladium complexes were characterized by techniques like 1H, 13C{1H} NMR, IR, and elemental analysis. The coordination modes of ligand with palladium precursor in complexes 5 and 6 were authenticated by single crystal X-ray diffraction. The complexes possess distorted square planar geometry around palladium center. Thermally robust and air stable complexes 5 and 6 were used as catalyst for regioselective arylation of imidazole and O-arylation of phenol. In case of regioselective arylation of imidazole, the reaction proceeds smoothly under mild reaction conditions, only 2.0 mol% of catalyst loading is required to achieve high yield (76–92%). This protocol is applicable to a broad substrate scope showing excellent tolerance towards different functional groups. Whereas for O-arylation of phenol also only 2.0 mol% catalyst loading is sufficient to give good yield (71–92%) with excellent tolerance towards a broad range of functional groups. Among sulfur and selenium coordinated ligands, selenium ligand coordinated complex, was found to outperform the catalytic reactions in both cases as compare to sulfur ligand. The mercury and triphenylphosphine poisoning tests suggest homogeneous nature of catalysis.

Cu(ii) complexes with tridentate sulfur and selenium ligands: catecholase and hydrolysis activity

Two new copper(ii) mononuclear complexes (CSe and CS) were synthesized and characterized by the following techniques: X-ray crystallography, elemental analysis, IR, EPR and UV-vis spectroscopies, conductimetric analysis and mass spectrometry.

Synthesis, characterization and biological evaluation of new manganese metal carbonyl compounds that contain sulfur and selenium ligands as a promising new class of CORMs.

Three new manganese carbonyl compounds with heavy atom donors were synthesized and their potential use as photoCORMS was evaluated. Interestingly, all compounds had an elusive binding mode, in which the ligands adopted a κ2-X coordination (where X = S or Se), confirmed both by X-ray crystallography and IR spectroscopy. The stability of the title compounds in the dark was determined by monitoring the changes in the UV spectra of the compounds in both dichloromethane and acetonitrile. These studies show that in coordinating solvents there is an exchange of the bromide bonded to the metal centre by a solvent molecule, which is evidenced by the changes in the UV and IR spectra and by DFT analysis. EDA and natural bond order analyses were conducted to evaluate the influence of the heavy atom donors in the first coordination sphere of the compounds. Photoexcitation at 380 nm demonstrated that all compounds showed release of all three COs, as seen in the photoproducts detected by IR spectroscopy. Furthermore, CO release was observed when the photoCORMs were incubated with living cells, and we observed a CO-dependent inhibition of cell viability.

Mixed‐Valent Selenium Ligands in the Uncharged Iridium Complexes [Ir4Se10Br16] and [Ir6Se8Cl30

AbstractThe reaction of Ir with Se and SeBr4 at 200 °C yields shiny vermillion slate‐like crystals of the new compound Ir4Se10Br16. Single‐crystal X‐ray diffraction revealed an orthorhombic unit cell, space group Pccn, with lattice parameters a = 1515.0(1) pm, b = 1534.4(1) pm, and c = 1514.5(1) pm at 296(1) K. The crystal structure consists of uncharged tetranuclear iridium complexes [Ir4Se10Br16] with C2 symmetry. In the [(Ir3+)4(μ4‐η2‐Se22–)2(μ‐ηSe‐[SeBr]–)2(ηSe‐SeBr2)4(μ‐Br–)2(Br–)4] complex, each of the iridium atoms is coordinated octahedrally by four selenium and two bromine atoms. Selenium adopts three different oxidation states: –I in the fourfold‐bonded diselenide dumbbell, ±0 in the bridging [SeBr]– unit, and +II in the terminal SeBr2 ligand. An analogous reaction with SeCl4 at 300 °C yields orange air‐stable crystals of Ir6Se8Cl30. The triclinic crystal structure [space group P$\bar {1}$, a = 891.2(1) pm, b = 1064.6(1) pm, c = 1263.0(1) pm, α = 94.458(3)°, β = 106.900(3)°, and γ = 101.410(3)° at 296(1) K] consists of uncharged hexanuclear iridium complexes with the structured formula [(Ir3+)6(μ‐ηSe‐[SeCl]–)2(ηSe‐SeCl2)6(μ‐Cl–)10(Cl–)6] and shows structural motifs similar to Ir4Se10Br16 and IrSeCl5. The triclinic structure of IrSeCl5 [P$\bar {1}$, a = 1223.4(1) pm, b = 1408.7(1) pm, c = 1499.5(1) pm, α = 115.72(1)°, β = 106.05(1)°, and γ = 96.38(1)° at 296(1) K] is homeotypic to monoclinic RhSCl5.

Synthesis, characterization, structures and cytotoxicity of platinum(II) complexes containing dimethylpyrazole based selenium ligands

A series of water soluble platinum(II) complexes of general formulae [Pt(en)(L)][NO3]2, [Pt(NH3)2(L)][NO3]2 [en=ethylenediamine; L=dmpzC6H4Se(CH2)nCOOH or dmpzCH2CH2Se(CH2)nCOOH (n=1 and 2)], [Pt(en)(L)][NO3][OH]·H2O [L=dmpzCH2CH2Se(CH2)nCOOH (n=1 and 2)] and [Pt(dmpzCH2CH2SeCH2CH2COOH)2][Cl]2·2H2O have been synthesized. They were characterized by microanalyses, IR, NMR (1H, 13C{1H}, 77Se{1H} and 195Pt{1H}) spectroscopy. Molecular structures of [Pt(en)(dmpzCH2CH2SeCH2COOH)][NO3][OH]·H2O and [Pt(dmpzCH2CH2SeCH2CH2COOH)2][Cl]2·2H2O were determined unambiguously by single crystal X-ray diffraction analyses. The cytotoxicity of these complexes has been evaluated against human colon (HT29, Colo205), ovarian (A2780) and bladder (T24) cancer cell lines and compared with the activity of cisplatin and adriamycin.

Palladium(ii) complexes bearing the 1,2,3-triazole based organosulfur/ selenium ligand: synthesis, structure and applications in Heck and Suzuki–Miyaura coupling as a catalyst via palladium nanoparticles

Air and moisture insensitive palladium complexes, [Pd(L)Cl2] (1/2), in which L = 1-benzyl-4-phenylthiomethyl or 1-benzyl-4-phenylselenomethyl-1H-1,2,3-triazole (L1 or L2) catalyze Heck (HC) and Suzuki–Miyaura coupling (SMC) reactions between a series of aryl bromides including deactivated bromides and n-butyl acrylate and phenylboronic acid, respectively. The optimal catalytic loading was found to be in the order of 0.01 mol%. HRTEM, TGA and EDX data indicated that 3–11 nm nanoparticles (NPs) composed of palladium and sulfur or selenium and protected with L or its fragment, were formed during the catalyzed reaction. The isolated NPs displayed catalytic activity and appeared to have a role in the catalysis. A two-phase test indicated that both homogeneous and heterogeneous catalysis took place. The complexes 1 and 2 were synthesized by the reactions of L1 and L2 respectively with [(MeCN)2PdCl2]. Their single crystal X-ray diffraction indicated that the geometry adopted by ligands around Pd in both complexes is distorted square planar with Pd–S and Pd–Se bond lengths of 2.2727(14) and 2.3693(8) Å, respectively. DFT calculation gave bond lengths and angles in keeping with the experimental values. The DFT calculated HOMO–LUMO energy difference is lower for 1 than for 2 in accordance with the observed higher catalytic activity of 1.

Anticancer Activity for Targeting Telomeric G-Quadruplex and Antiangiogenesis of a Novel Ru(II)–Se Complex

A new Ru(II)-Se complex, Ru(bpy)2L2Cl2 (bpy = 2,2'-bipyridine, L = 1,10-phenanthrolineselenazole) (Ru-Se) has been synthesized and characterized. The G-quadruplex DNA-binding properties of the complex and its selenium ligand (Phen-Se) were evaluated by thermal denaturation study, polymerase chain reaction (PCR) stop assay, and telomerase repeat amplification protocol (TRAP). The results showed that the obtained complex could induce and stabilize G-quadruplex structure as well as exhibit potent inhibitory activity against telomerase. In vitro cytotoxicity studies showed that complex Ru-Se inhibited the cancer cell growth through apoptosis. However, the presence of the ligand Phen-Se did not appear to have a significant effect either on G-quadruplex binding or on biological activity. Furthermore, the cell migration assay and the tube formation assay also demonstrated that the complex Ru-Se significantly inhibited human umbilical vascular endothelial cell (HUVEC) proliferation, migration, and tube formation. These findings indicate that the Ru-Se complex may be a potential telomerase inhibitor and a viable drug candidate in antiangiogenesis for anticancer therapies.

Half-Sandwich Ruthenium(II) Complexes of Click Generated 1,2,3-Triazole Based Organosulfur/-selenium Ligands: Structural and Donor Site Dependent Catalytic Oxidation and Transfer Hydrogenation Aspects

1-Benzyl-4-((phenylthio)-/(phenylseleno)methyl)-1H-1,2,3-triazole (L1/L2) and 4-phenyl-1-((phenylthio)-/(phenylseleno)methyl)-1H-1,2,3-triazole (L3/L4) synthesized using the click reaction have been reacted for the first time with [{(η6-C6H6)RuCl(μ-Cl)}2] and NH4PF6 to design the half-sandwich complexes [(η6-benzene)RuLCl]PF6 (1–4 for L = L1–L4), which have been characterized by single-crystal X-ray diffraction and explored for the catalytic oxidation of alcohols with N-methylmorpholine N-oxide (NMO) and transfer hydrogenation of ketones with 2-propanol. There is a pseudo-octahedral “piano-stool” disposition of donor atoms around Ru in 1–4. In 1 and 2, N(3) of the triazole skeleton coordinates with Ru, whereas in other complexes the nitrogen involved is N(2). The Ru–S and Ru–Se bond distances are 2.3847(11)/2.3893(10) and 2.497(5)/2.4859(9) A, respectively. The catalytic processes are more efficient with 3 and 4 (compared to 1 and 2), in which N(2) of the triazole is involved in coordination with Ru. The ...

Didocosyl selenide stabilized recyclable Pd(0) nanoparticles and coordinated palladium(ii) as efficient catalysts for Suzuki–Miyaura coupling

First selenium ligand stabilized Pd(0) nanoparticles (∼3-5 nm) catalyze Suzuki-Miyaura C-C coupling in short time and are recyclable (up to 94% yield after 5 reuses). The air stable compound [PdCl(2)(L1)(2)] shows high catalytic efficiency for this coupling as its 3 × 10(-5) mol% is sufficient for activated ArBr.

Tetradentate selenium ligand as a building block for homodinuclear complexes of Pd(ii) and Ru(ii) having seven membered rings or bis-pincer coordination mode: high catalytic activity of Pd-complexes for Heck reaction

1,2,4,5-Tetrakis(phenyselenomethyl)benzene (L) has been synthesized by reaction of in situ generated PhSe(-) with 1,2,4,5-tetrakis(bromomethyl)benzene in N(2) atmosphere. Its first bimetallic complexes and a bis-pincer complex having compositions [(η(3)-C(3)H(5))(2)Pd(2)(L)][ClO(4)](2) (1) [Pd(2)(C(5)H(5)N)(2)(L)][BF(4)](2) (2) and [(η(6)-C(6)H(6))(2)Ru(2)(L)Cl(2)][PF(6)](2) (3) have been synthesized by reacting L with [Pd(η(3)-C(3)H(5))Cl](2), [Pd(CH(3)CN)(4)][BF(4)](2) and [(η(6)-C(6)H(6))(2)RuCl(2)](2) respectively. The structures of ligand L and its all three complexes have been determined by X-ray crystallography. In 1 and 3, ligand L forms with two organometallic species seven membered chelate rings whereas in 2 it ligates in a bis-pincer coordination mode. The geometry around Pd in 1 or 2 is close to square planar whereas in 3, Ru has pseudo-octahedral half sandwich "Piano-Stool" geometry. The Pd-Se bond distances are in the ranges 2.4004(9)-2.4627(14) Å and follow the order 1 > 2, whereas Ru-Se bond lengths are between 2.4945(16) and 2.5157(17) Å. The 1 and 2 have been found efficient catalysts for Heck reaction of aryl halides with styrene and methyl acrylate. The 2 is superior to 1. The TON and TOF values (per Pd) are up to ~47500 and ~2639 h(-1) respectively.

Catalyst Leaching as an Efficient Tool for Constructing New Catalytic Reactions: Application to the Synthesis of Cyclic Vinyl Sulfides and Vinyl Selenides

AbstractCatalyst leaching from Pd and Ni particles stabilized by organic sulfur and selenium ligands occurs in solution in the presence of phosphanes. This process has been monitored in real time by 1D and 2D NMR spectroscopy and the nature of the metal species established. This catalyst leaching is shown to be a powerful tool for generating new catalytic activity from species formed in situ where the parent bulk particles are inactive. The catalytic system developed has been successfully implemented in a novel synthetic procedure that provides new types of cyclic sulfur and selenium compounds in high yields through the reaction between alkynes and dichalcogenides. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Syntheses and Structures of Solvated Tetrasodiumtetrachalcogenostannates [Na4(en)4]]SnE4] (en = 1,2‐Diaminoethane; E: Te, Se), and Their Reactions Toward Further Ternary or Quaternary Chalcogenometallates [Mn(en)3]2 [Sn2Te6]×4H2O or [Na10(H2O)34] [Mn4(μ4‐Se)(SnSe4)4

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