Effect of the Composition of Ethanol–DMSO Solvents on the Stability of Silver(I) Complexes with 18-Crown-6

The effect of composition of ethanol–dimethyl sulfoxide (EtOH–DMSO) solvents (χ_DMSO = 0.0–1.0 mole fractions) on the stability of silver(I) complexes with 18-crown-6 ether (18C6) has been studied potentiometrically at 298.15 K. The increasing of DMSO concentrations in mixed solvents are shown to considerably reduce the stability of 18C6 complexes with silver(I) ion ([Ag18C6]⁺). A change in the solvation state of the central ion is suggested to be the key factor in shifting complexing equilibrium.     

Complex formation of silver(I) with glycinate ion in aqueous ethanol and dimethyl sulfoxide solutions

The complex formation reaction of silver(I) with glycinate ion in aqueous ethanol and dimethyl sulfoxide solutions of variable compositions was studied by potentiometric titration at 298 K. The stabilities of Ag(I) glycinate complexes were found to increase with the increasing content of the organic cosolvent. The contribution of ΔG° of the reagent resolvation to the change in the Gibbs energy of the complex formation reaction was estimated using the literature data. The change in the ligand solvate state was shown to give the main contribution to the stability of the title complexes in water-organic solvents.     

The influence of solvation on the stability constants of Ag<Superscript>+</Superscript>-18-crown-6 complexes in acetonitrile-dimethylsulfoxide mixtures at 298.15 K

The influence of the composition of acetonitrile-dimethylsulfoxide solvents on the stability of silver(I) complexes with 18-crown-6 ether was studied potentiometrically. An increase in the concentration of dimethylsulfoxide decreased the stability of the coordination compound. It was shown on the basis of the thermodynamic characteristics of solvation of the reagents that a determining factor of complex formation equilibrium shifts was the solvation effect of the Ag⁺ ion. An equation was suggested for predicting the stability of silver(I) coordination compounds with crown ethers and pyridine-type ligands in binary mixtures of aprotic solvents from changes in the solvation state of the central ion.     

Review: Multimetallic silver(I)–pyridinyl complexes: coordination of silver(I) and luminescence

This review highlights some structural features and luminescent properties of homo- and hetero-multinuclear silver(I)–pyridinyl complexes. It focuses on the coordination and geometry of the silver(I) ions to the pyridinyl-nitrogen. For this reason, we have considered only pyridinyl-N–Ag(I) complexes whose crystal data are available. In addition, this review does not consider mononuclear silver(I)–pyridinyl complexes as these have been reviewed elsewhere. This is motivated by the fact that multinuclear silver(I)–pyridinyl complexes have been shown to be more stable in solution, possess enhanced properties, and have fascinating structures compared to their mononuclear counterparts. The introduction highlights pyridinyl ligands used in complexation of silver(I) ions. The main body highlights complexation of silver(I) through pyridinyl nitrogen and the interactions found in the multinuclear silver(I)–pyridinyl complexes as well as the coordination number and geometry of silver(I) centers. Though silver(I) has been flaunted to prefer linear twofold coordination geometry, from this review, it is clear that higher coordination numbers in varied geometries are possible. These include distorted trigonal planar, T-shaped, distorted tetrahedral, trigonal bipyramidal, and octahedral geometries. Coordination of silver(I) to pyridinyl ligands and their metalloligands has been observed to impart or enhance luminescent properties in the ensuing complexes.     

Catalytic Activity of Cationic and Neutral Silver(I)–XPhos Complexes with Nitrogen Ligands or Tolylsulfonate for Mannich and Aza‐Diels–Alder Coupling Reactions

Cationic and neutral silver(I)–L complexes (L=Buchwald‐type biaryl phosphanes) with nitrogen co‐ligands or organosulfonate counter ions have been synthesised and characterised through their structural and spectroscopic properties. At room temperature, both cationic and neutral silver(I)–L complexes are extremely active catalysts in the promotion of the single and double A³ coupling of terminal (di)alkynes, pyrrolidine and formaldehyde. In addition, the aza‐Diels–Alder two‐ and three‐component coupling reactions of Danishefsky’s diene with an imine or amine and aldehyde are efficiently catalysed by these cationic or neutral silver(I)–L complexes. The solvent influences the catalytic performance due to limited complex solubility or solvent decomposition and reactivity. The isolation of new silver(I)–L complexes with reagents as ligands lends support to mechanistic proposals for such catalytic processes. The activity, stability and metal–distal arene interaction of these silver(I)–L catalysts have been compared with those of analogous cationic gold(I) and copper(I) complexes.     

Coordination polymers from kinetically labile copper(I) and silver(I) complexes: true macromolecules or solution aggregates?

Copper(I) and silver(I) coordination polymers have been prepared via conversion of equimolar amounts of o‐phenanthroline‐based bis‐bidentate ligand monomers, and [Cu(CH₃CN)₄]PF₆ or AgBF₄ as the respective metal comonomers. Using NMR spectroscopy, the homogeneous constitution of the diamagnetic products has been proved, and their average chain length has been estimated to be P_n ≥ 20. Moreover, NMR studies showed the multinuclear complexes to be open (dynamic) solution aggregates when dissolved in solvents that contain coordinating species like acetonitrile or pyridine. When strictly non‐coordinating solvents are used, on the other hand, the multinuclear complexes were found to be “true” polymers, i.e. macromolecules with a constant number of repeating units per individual chain in time. At very high dilution, finally, transformation of the originally formed chain molecules into cyclic oligomers was observed when coordinating solvents are used, but not in the case of non‐coordinating solvents.     

Phosphate ligands in the gold(I)-catalysed activation of enynes

Gold(I) forms neutral complexes with binol phosphates that are unreactive in the catalytic cyclisation of enynes. Reaction in protic solvents or activation by silver(I) restores the catalytic activity.     

Potentiometric determination of successive stability constants of ethylenediamine complexes of several metals in dimethylsulphoxide

The stability constants of the complexes of silver(I), zinc(II), cadmium(II) and manganese(II) with ethylenediamine in dimethylsulphoxide at 25 degrees and ionic strength 0.1Mhave been determined potentiometrically. The stability constants are consistently larger in DMSO than in water as expected from the difference in dielectric constant for the two solvents.     

Silver(I) and gold(I) complexes of rhodanine

Summary Some rhodanine (HL) complexes of silver(I) and gold(1) have been prepared and studied by conductivity measurements and by i.r. spectroscopy. Structures for the complexes are proposed.     

Lyotropic mesomorphism in some thermotropic,polycatenar complexes of silver(I)

A wide range of mesophases are induced on treating polycatenar complexes of silver(I) with a wide range of organic solvents.     

Complexing properties of N-2-sulfoethyl chitosans

For a new sulfoethylated chitosan derivative with the degree of substitution of amino group hydrogen atoms of 0.5, the dissociation constant of functional groups has been determined by potentiometric titration. Complexing properties of sulfoethylated chitosan toward copper(II), cobalt(II), nickel(II), zinc(II), manganese(II), cadmium(II), silver(I), lead(II), magnesium(II), calcium(II), strontium(II), and barium(II) ions have been studied potentiometrically. Alkaline earth and magnesium ions do not form complexes with sulfoethylated chitosan. For the other ions, stability constants of the resulting complexes have been determined. The most stable N-2-sulfoethyl chitosan complexes are those with copper(II) and silver(I) ions.     

Is the silver–alkene interaction a useful new supramolecular synthon?

The use of the silver–alkene interaction in coordination and supramolecular chemistry is surveyed in this review. Although organometallic complexes of ethene date back almost 200 years to the historic example of Zeise's platinum salt, the use of alkenes as donor ligands for silver(I) has a much more recent history. A diverse range of interesting silver–ethene complexes have been reported in recent years, whilst numerous discrete silver(I) complexes of structurally diverse olefinic ligands have been the subject of much study over the last fifty years. More recently, ligands containing multiple alkene subunits have been used for the synthesis of 0-, 1-, 2- and 3D supramolecular assemblies, which is the major focus of this review.     

Silver(I) complexes with oxazoline-containing tripodal ligands: structure variation via counter anions and reaction conditions

Seven new silver(I) complexes of the formula [Ag2(L)2(CF3SO3)2] (1), [Ag2(L)2(CH3SO3)2] (2) [Ag2(L)2](BF4)2 (3), [Ag3(L)2(NO3)2]NO3.5H2O (4), [Ag2(L)(NO3)2].CH3OH (5), [Ag2(L)2](ClO4)2 (6) and [Ag3(L)2(CH3CN)3](ClO4)3 (7) have been synthesized by reactions of 1,3,5-tris(2-oxazolinyl)benzene (L) with varied silver(I) salts under different conditions. The influences of counter anions and reaction conditions on the structure of the complexes are discussed. Three complexes , 1, 2 and 3 with two kinds of different 1D chain structures were obtained under the same synthetic conditions by using different silver(I) salts, and the ligand L was found to adopt bis-monodentate (1 and 2) and tris-monodentate (3) coordination modes respectively. On the other hand, by using the same silver(I) nitrate or silver(I) perchlorate but different reaction solvents, 4 and 5 or 6 and 7 were isolated respectively. Complexes 4and 5 have different 1D chain structures, and 6 is isostructural with . However, 7 is a tri-nuclear, propeller-shaped M3L2 supramolecular capsule in which L adopts a cis,cis,cis-conformation, while the ligand L in 3-6 has cis,trans,trans-conformation. The results revealed that the nature of the counter anions, such as their size, coordination ability and coordination mode, and the reaction conditions all have great impact on the structure of the complexes. The complexes were also characterized by electrospray mass spectrometry. Furthermore, complex 7 exhibited modest second-harmonic-generation (SHG) efficiency.     

Competitive transport of seven metal cations through bulk liquid membrane using 5,12-di(phenoxymethyl)-1,4-dioxa-7, 10-dithiacyclododecane-2,3-dione as carrier

The competitive metal ion transport of copper(II), cobalt(II), zinc(II), cadmium(II), silver(I), chromium(III) and lead(II) with a S-O donor compound was examined. Competitive transport experiments involving the metal cations from an aqueous source phase through an organic membrane into an aqueous receiving phase have been carried out using 5,12-di(phenoxymethyl)-1,4-dioxa-7,10-dithiacyclododecane-2,3-dione as the ionophore present in the organic phase. Fluxes and selectivities for competitive metal cations transport across bulk liquid membranes have been determined in a variety of chlorinated hydrocarbon and aromatic hydrocarbon solvents. The membrane solvents include: dichloromethane (DCM), chloroform (CHCl₃), 1,2-dichloroethane (1,2-DCE), and nitrobenzene (NB) and also in chloroform-dichloromethane (CHCl₃-DCM) and chloroform-nitrobenzene (CHCl₃-NB) binary mixtures. Although the selectivity for silver(I) cation in all of these organic solvents is fundamentally similar, but the most transport rate for Ag(I) was obtained in dichloromethane. The sequence of transport rate for silver ion in organic solvents was: DCM > CHCl₃ > 1,2-DCE > NB. A linear relationship was observed between the transport rate of silver ion and the composition of CHCl₃-DCM, but a non-linear behavior was observed in the case of CHCl₃-NB binary solution. The influence of the stearic, palmetic and oleic acids as surfactant in the membrane phase on the transport of the metal cations was also investigated.     

Synthesis and biological activity of ester- and amide-functionalized imidazolium salts and related water-soluble coinage metal N-heterocyclic carbene complexes

N-Heterocyclic carbene (NHC) ligand precursors, namely, HIm(A)Cl [1,3-bis(2-ethoxy-2-oxoethyl)-1H-imidazol-3-ium chloride] and HIm(B)Cl {1,3-bis[2-(diethylamino)-2-oxoethyl]-1H-imidazol-3-ium chloride}, functionalized with hydrophilic groups on the imidazole rings have been synthesized and were used in the synthesis of corresponding carbene complexes of silver(I) and copper(I), {[Im(A)]AgCl}, {[Im(A)]CuCl}, and {[Im(B)](2)Ag}Cl. Related Au(I)NHC complexes {[Im(A)]AuCl} and {[Im(B)]AuCl} have been obtained by transmetalation using the silver carbene precursor. These compounds were characterized by several spectroscopic techniques including NMR and mass spectroscopy. HIm(B)Cl and the gold(I) complexes {[Im(A)]AuCl} and {[Im(B)]AuCl} were also characterized by X-ray crystallography. The cytotoxic properties of the NHC complexes have been assessed in various human cancer cell lines, including cisplatin-sensitive and -resistant cells. The silver(I) complex {[Im(B)](2)Ag}Cl was found to be the most active, with IC(50) values about 2-fold lower than those achieved with cisplatin in C13*-resistant cells. Growth-inhibitory effects evaluated in human nontransformed cells revealed a preferential cytotoxicity of {[Im(B)](2)Ag}Cl versus neoplastic cells. Gold(I) and silver(I) carbene complexes were also evaluated for their ability to in vitro inhibit the enzyme thioredoxin reductase (TrxR). The results of this investigation showing that TrxR appeared markedly inhibited by both gold(I) and silver(I) derivatives at nanomolar concentrations clearly point out this selenoenzyme as a protein target for silver(I) in addition to gold(I) complexes.     

Tris{2‐[N‐(diethylaminothiocarbonyl)benz(‐amidino;‐imidoxy;‐imidothio)‐N′‐yl]ethyl}amine – neue tripodale Liganden. Darstellung,Komplexstabilität und Extraktionsverhalten ihrer Silber(I)‐Komplexe

Tris{2‐[ N ‐(diethylaminothiocarbonyl)benz(‐amidino; imidoxy; ‐imidothio)‐ N ′‐yl]ethyl}amines – New Tripodal Ligands. Synthesis, Complex Stability, and Extraction Behaviour of their Silver(I) Complexes N‐(Thiocarbamoyl)‐benzimidoylchlorides react with trivalent nucleophiles to give four novel tripodal ligands. Two of them have been characterized by X‐ray methods. The ligands form with silver(I) cationic mononuclear complexes in which the three arms of the ligand are coordinated monodentately via sulfur. The results of FAB and ESI mass spectrometry as well as ESCA and NMR investigations verify this binding mode. The protonation constants of the ligands and the stability constants of silver(I) complexes have been determined potentiometrically. The novel tripodal compounds behave as powerful extractands for silver(I).     

Tetraphosphinitoresorcinarene complexes: cationic silver(I) and copper(I) halide complexes as mercurate(II) anion receptors

The reactions of mercury(II) halides with the tetraphosphinitoresorcinarene complexes [P4M5X5], where M=Cu or Ag, X=Cl, Br, or I, and P4=(PhCH2CH2CHC6H2)4(O2CR)4(OPPh2)4 with R=C6H11, 4-C6H4Me, C4H3S, OCH2CCH, or OCH2Ph, have been studied. The reactions of the complexes with HgX2 when M=Ag and X=Cl or Br occur with elimination of silver(I) halide and formation of [P4Ag2X(HgX3)], but when M=Ag and X=I, the complexes [P4Ag4I5(HgI)] are formed. When M=Cu and X=I, the products were the remarkable capsule complexes [(P4Cu2I)2(Hg2X6)]. When M=Ag and X=I, the reaction with both CuI and HgI2 gave the complexes [P4Cu2I(Hg2I5)]. Many of these complexes are structurally characterized as containing mercurate anions weakly bonded to cationic tetraphosphinitoresorcinarene complexes of copper(I) or silver(I) in an unusual form of host-guest interaction. In contrast, the complex [P4Ag4I5(HgI)] is considered to be derived from an anionic silver cluster with an iodomercury(II) cation. Fluxionality of the complexes in solution is interpreted in terms of easy, reversible making and breaking of secondary bonds between the copper(I) or silver(I) cations and the mercurate anions.     

The structure of the paramagnetic impurities in triglycine sulfate single crystals

ENDOR investigations of the bis(glycinato)-Cu(II) (NH₂CH₂COO)₂Cu and bis(glycinato)-oxo-V(IV) (NH₂CH₂COO)₂VO complexes in the ferroelectric triglycine sulfate (TGS) single crystals are reported. Magnetic hyperfine constants of the ligand nuclei are given. The ENDOR investigati confirm the conclusion derived from EPR studies that the copper and vanadyl ions occupy interstitial lattice sites forming bis(glycinato) complexes wit triclinic symmetry C₁. Molecular theoretical calculations of the EPR and ENDOR parameters of different paramagnetic impurities in TGS were performe using the self-consistent charge and configuration (SCCC) version of the extended Hückel theory (EHT). By using perturbation theory the parameters of the spin hamiltonian were determined.     

Effect of the composition of dimethyl sulfoxide–acetonitrile solvent on the stability of silver(I) complexes with 2,2'-bipyridyl

The effect of composition of the dimethyl sulfoxide–acetonitrile solvent on the shift in complexation equilibrium of silver(I) and 2,2'-bipyridyl was studied potentiometrically at 298.15 K. The stability of mono- and bis(bipyridyl) complexes of silver(I) was found to rise with increasing acetonitrile content in the mixed solvent. The difference in changes in the solvation state of the central and complex ions (the solvation effect of ions) was found to make a major contribution to the changes in stability of silver(I) complexes with 2,2'-bipyridyl in dimethyl sulfoxide–acetonitrile binary solvent.     

Preparation and X-ray crystal structure of a silver sandwich complex of an aza-thia macrocycle

During the course of studies directed towards the synthesis of kinetically stable silver(I) complexes, we have prepared a hexadentate bis-[9]-NS₂ ligand (1) which may be expected to form a series of stable octahedral complexes with many transition metal ions. The silver(I) complex has been characterized spectroscopically and crystallographically.