Tetrahedral Silver Research Articles

Photochemistry and photophysics of the tetrahedral silver(i) complex with diphosphine ligands: [Ag(dppb)2]PF6 (dppb = 1, 2-bis[diphenylphosphino]benzene)

The photophysical and photochemical properties of [Ag(dppb)2]PF6 (1) having a tetrahedral coordination geometry have been described.

Structural Variations of Silver Ethylene Complexes Supported by Boron-Protected Fluorinated Scorpionates and the Isolation of a Ligand-Directed Silver Helix

Silver(I) ethylene adducts [PhB(3-(CF3)Pz)3]Ag(C2H4) and [MeB(3-(CF3)Pz)3]Ag(C2H4) have been synthesized using the corresponding lithium salts, AgOTf, and ethylene. X-ray data show that [PhB(3-(CF3)Pz)3]Ag(C2H4) has a planar three-coordinate silver center whereas [MeB(3-(CF3)Pz)3]Ag(C2H4) features a tetrahedral silver site. The ethylene-free {[PhB(3-(CF3)Pz)3]Ag}n adopts a helical structure with a hexagonal pore.

Anion- and Solvent-Directed Assembly in Silver Bis(thioimidazolyl)methane Chemistry and the Silver−Sulfur Interaction

The effect of metal complexation on the structure and properties of the electroactive bis(1-methylthioimidazolyl)methane linkage isomers CH2(N-tim)2 (L1) and CH2(S-tim)2 (L2) has been explored. Coordination polymers {[Ag(L1)2]X}n (X = BF4, PF6) are formed by bridging L1 between tetrahedral silver centers giving two-dimensional cationic sheets composed of AgS(4) linkages; the anions are sandwiched between sheets. Cyclic dimers {[Ag2(L2)2]X2} (X = BF4, PF6, OSO2CF3) are formed when L2:AgX ratios are lower than 1.5. When L2:AgPF6 was 1.5 or higher, the complex [Ag4(L2)5](PF5)4 could be isolated as a solvate. The NMR, IR, electrochemical, and ESI+ mass spectral data of this latter compound indicate that extensive dissociation to the cyclic dimer and free ligand occurs in solution. Finally, a Cambridge Structural Database search was performed to provide insight into reasonable silver-sulfur bond distances, since literature values appeared to vary widely between 2.3 and 3.2 A. It was found that these distances increase with increasing coordination number of silver. The average distances for 2-, 3-, 4-, 5-, and 6-coordinate silver were found to be 2.40, 2.52, 2.62, 2.70, and 2.75 A, respectively.

Antimicrobial properties of highly fluorinated silver(I) tris(pyrazolyl)borates

Highly fluorinated tris(pyrazolyl)borate ligand [HB(3,5-(CF 3) 2Pz) 3] − has been used in the isolation of air- and light-stable silver complex, [HB(3,5-(CF 3) 2Pz) 3]Ag(OSMe 2). It is a monomeric tetrahedral silver complex with an O-bonded dimethylsulfoxide ligand. The silver adduct [HB(3,5-(CF 3) 2Pz) 3]Ag(OSMe 2) and the related [HB(3,5-(CF 3) 2Pz) 3] Ag(THF) (where OSMe 2 = dimethyl sulfoxide; THF = tetrahydrofuran) show good antibacterial activity, and their antimicrobial efficacy against Staphylococcus aureus is greater than those of AgNO 3 and silver sulfadiazine.

Anion-Dependent Silver(I) Coordination Polymers of the Tridentate Pyridylphosphonite: PPh(3-OCH2C5H4N)2

Three new multidimensional coordination polymers have been constructed from the reaction of AgX, where X = OTf-, BF4-, or tfa-, with the novel phosphonite PhP(3-OCH2C5H4N)2, PCP-32, 1. It is seen that regardless of the ratio of reactants mixed, polymeric growth of the compounds always reveals a ligand-to-metal ratio of 1:2 for PCP-32AgOTf, 2, 1:1 for PCP-32AgBF4, 3, and 1:2 for PCP-32Ag(tfa), 4. The coordination number, metal environment, ligand conformation, and polymer dimensionality are found to vary greatly from 2 to 4 and are dependent upon the anion present. Coordination numbers from 2 to 4, representing linear, trigonal, and distorted tetrahedral environments are displayed. PCP-32AgOTf polymerizes as a linear chain containing both two- and four-coordinate silvers, PCP-32AgBF4 repeats a single trigonal motif throughout its structure, and PCP-32Ag(tfa) shows two unique distorted tetrahedral silver centers. Ligand flexibility allows for cross-ligand Ag-Ag distances to range from 3.1918(8) to 14.015(2) A. The coordination polymers have been characterized by elemental analysis, variable-temperature multinuclear NMR spectroscopy, single-crystal X-ray diffraction, and fluorometric studies.

Nature and catalytic role of active silver species in the lean NO x reduction with C 3H 6 in the presence of water

A study of the lean NO x reduction activity with propene in the presence of water over Ag/Al 2O 3 catalysts with different silver loadings (1.5–6 wt%) has been done using X-ray diffraction, ultraviolet–visible spectroscopy, transmission electron microscopy, and in situ diffuse reflectance infrared and X-ray absorption spectroscopies under reaction conditions. The catalysts were prepared by an impregnation method employing EDTA complexes that allow highly dispersed silver phases to be obtained, which are stabilized under reaction conditions by strong interactions with the support. It is shown that the active species corresponds to silver aluminate-like phases with tetrahedral local symmetry. The role of silver in the reaction mechanism is shown to be mainly in the activation of NO x and propene species. In particular, the silver entities have been found to offer a new reaction path for propene activation which involves generation of acrylate species as a partially oxidized active intermediate. Differences between two active catalysts containing 1.5 and 4.5 wt% of Ag suggest that optimization of the SCR activity can be related to the oxygen lability of the tetrahedral silver aluminate-like phase present in the catalyst. As postulated previously, the high nonselective propene oxidation activity of the highest loaded sample (with 6 wt% Ag) appears to be related to formation of metallic silver surface states at low reaction temperatures which are active for NO dissociation.

Synthesis, structure, and thermal behavior of discrete Co(II), Ag(I), and Pd(II) complexes with 2,3-bis(2-pyridyl)quinoxaline. Insight into coordination modes

The reactions of 2,3-bis(2-pyridyl)quinoxaline (bpq) with CoCl 2·6H 2O, Ag(CH 3CN) 4BF 4, and PdCl 2(C 6H 5CN) 2 produce [CoCl 2(bpq)] 2·2CHCl 3, [Ag(bpq)CH 3CN] 2(BF 4) 2·2CH 3CN, and [PdCl 2(bpq)], respectively. All the products are discrete 1:1 (metal:bpq) adducts, where the chelation mode of the bpq is dependent upon the metal atoms. The structure of [CoCl 2(bpq)] 2·2CHCl 3 is a centrosymmetric Cl-bridged four-membered dimer, [Co 2Cl 2], in which the bpq is bonded to the cobalt(II) atom in an anisobidentate mode with the nitrogen donors of pyridine and pyrazine rings. For [Ag(bpq)CH 3CN] 2(BF 4) 2·2CH 3CN, each bpq ligand connects two tetrahedral silver(I) ions in a tridentate mode, resulting in a cationic cyclic dimer. The structure of [PdCl 2(bpq)] approximates to a molecular rocking chair with an isobidentate bpq through the nitrogen donors of 2-pyridyl rings. The compounds exhibit significant and characteristic relationships between the structures and their thermal properties. For [CoCl 2(bpq)] 2·2CHCl 3, the solvate chloroform molecules are safely contained up to 144°C, but drastically evaporate above this temperature. The striking feature of [Ag(bpq)CH 3CN] 2(BF 4) 2·2CH 3CN is that the skeletal cyclic dimer is basically retained after dissociation of the coordinated acetonitriles in the solid state.

Silver(I)–3,6-bis(pyridin-3-yl)-1,2,4,5-tetrazine coordination polymers: a diversity of chain motifs

The influence of solvent and anion on the formation of coordination polymers between silver(I) and 3,6-bis(pyridin-3-yl)-1,2,4,5-tetrazine (3,3′-pytz), a bridging ligand that can adopt both cisoid and transoidconformations, is reported. Reaction of AgPF 6 in MeCN with 3,3′-pytz in CH 2Cl 2 gives ([{Ag(NCMe) 2}(μ-3,3′-pytz)][PF 6]·MeCN) ∞, 1, of AgPF 6 in MeNO 2 and 3,3′-pytz in CH 2Cl 2 gives ([{Ag 2(μ-3,3′-pytz) 2}(μ-3,3′-pytz)][PF 6] 2·4MeNO 2) ∞, 2, and of AgCF 3SO 3 in MeCN and 3,3′-pytz in CH 2Cl 2 gives {[Ag(μ-3,3′-pytz)]CF 3SO 3} ∞, 3. These cationic coordination polymers exclusively form chain structural motifs. That in 1, ([{Ag(NCMe) 2}(μ-3,3′-pytz)] +) ∞, has a castellated construction with each tetrahedral silver(I) center coordinated by two solvent molecules as well as two linking transoid-oriented 3,3′-pytz bridges (Ag⋯Ag 13.210 Å) in a 1:1 polymeric chain. That in 2, ([{Ag 2(μ-3,3′-pytz) 2}(μ-3,3′-pytz)] 2+) ∞, is novel. It is the first coordination polymer to exhibit both cisoid and transoid conformations of a bridging ligand coordinated to the same metal center. Pairs of silver(I) centers are linked by pairs of cisoid-oriented 3,3′-pytz molecules (Ag⋯Ag = 11.695 Å) to form [Ag 2(μ-3,3′-pytz) 2] motifs, which are bridged, in turn, by transoid-oriented 3,3′-pytz molecules (Ag⋯Ag = 13.318 Å) to form a 3:2 ligand:metal infinite polymeric zigzag chain. That in 3, {[Ag(μ-3,3′-pytz)] +} ∞, has a zigzag architecture despite being based on linear silver(I) centers. Transoid-oriented 3,3′-pytz molecules link silver(I) centers (Ag⋯Ag 13.225 Å) to give a 1:1 ligand:metal infinite polymeric zigzag chain. The chains aggregate in parallel pairs linked by weak Ag⋯Ag contacts (Ag⋯Ag = 3.220 Å), which are supported by (μ 2-κO,κO′) bridging CF 3SO 3 − anions.

Superlattices of Self-Assembled Tetrahedral Ag Nanocrystals

The packing in self-assembled nanocrystal superlattices is determined to a large extent by the geometry of the nanocrystals, as is demonstrated here by the preparation and analysis of wellordered arrays of predominantly tetrahedral silver nanocrystals. The Figure shows the model proposed to explain the monolayer self-assembly of tetrahedral silver nanocrystals passivated by bundled thiolate molecules.

Nitrogen Base Adducts with Silver(I) p-Toluenesulfonate: Syntheses and Single Crystal X-ray Characterizations of the Adducts with Pyridine (1:1), 2-Aminopyridine (1:2), 2-Aminopyrimidine (1:1), 4,6-Dimethyl-2-aminopyrimidine (2:3), and 3-Aminobenzoic Acid (1:2) and the Crystal Structure of the Parent Silver(I) p-Toluenesulfonate

The complex adducts of silver(I) p-toluenesulfonate, [Ag(pts)], with the nitrogen bases pyridine (1:1), [{Ag(pts)}(py)]n (2), 2-aminopyridine (2:4), [{Ag(pts)}2(2-apy)4] (3), 2-aminopyrimidine (1:1), [{Ag(pts)}(2-ap)]n (4), 4,6-dimethyl-2-aminopyrimidine (2:3), [{Ag(pts)}2(dmap)3]n (5), and 3-aminobenzoic acid (2:4), [{Ag(pts)}2(3-aba)4] (6), have been prepared and their structures, together with that of the parent compound, silver(I) p-toluenesulfonate (1), determined by X-ray diffraction. Crystals of 1 (C14H14Ag2O6S2) are monoclinic, space group P21/a, Z = 2, with a = 8.596(3) Å, b = 6.0330(4) Å, c = 15.363(4) Å, and β = 93.03(1)°. The polymeric structure is based on bis(sulfonato-(O,O‘) bridged dimers analogous to those found in some of the O,O‘-bridged silver(I) carboxylates, these also having pseudo trigonal bipyramidal AgO4 centers. All sulfonate oxygens are utilized in coordination. The structures of the monoheteroaromatic nitrogen donor group adducts (2, 3, and 6) are either polymeric [2 (C12H12AgNO3S): AgN2O2 centers] or discretely dimeric [3 (C34H38Ag2N8O6S2) and 6 (C42H42Ag2N4O14S2): both AgN2O2] and can be considered the result of replacement of either one or two oxygen sites about the silver in [Ag(pts)] by nitrogen donors, with subsequent rearrangement about very distorted tetrahedral silver centers. For 2, crystals are monoclinic, space group P21, Z = 2, with a = 9.1237(8) Å, b = 5.553(1) Å, c = 12.439(1) Å, and β = 91.182(8)°. For 3, crystals are triclinic, space group P1̄, Z = 1, with a = 8.635(3) Å, b = 10.434(3) Å, c = 11.138(3) Å, α = 104.89(2), and β = 90.20(2)°, γ = 99.94(2)°. For 6, crystals are monoclinic, space group P21/a, Z = 4, with a = 8.006(2) Å, b = 31.675(8) Å, c = 8.803(2) Å, and β = 104.413(9)°. Hydrogen-bonding interactions via the second functional group in both 3 and 6 give additional lattice stability. However, with the bifunctional heteroaromatic pyrimidines, extension of the polymer structures occurs through both ring nitrogens to give either a simple ribbon polymer (4, C11H12AgN3O3S) (trigonal planar AgON2 repeat) or a pyrimidine-linked, sulfonate-bridged eight-membered cyclic dimer unit, in which the tetrahedral Ag2O2N2 centers incorporate an additional unidentate pyrimidine (5, C32H41Ag2N9O6S2). For 4, crystals are monoclinic, space group P21/n, Z = 4, with a = 6.535(2) Å, b = 7.3440(8) Å, c = 26.13(1) Å, and β = 90.44(1)°: For 5, crystals are monoclinic, space group C2/c, Z = 4, with a = 21.312(6) Å, b = 10.650(1) Å, c = 17.565(5) Å, and β = 110.58(1)°. Hydrogen bonding is also significant in lattice stabilization in both of these structures. The preparation of an unstable adduct of Ag(pts) with aniline, [{Ag(pts)}(an)3] 7, is also reported, and infrared spectroscopy indicates that it is has both amine-bonded aniline as well as uncoordinated aniline.

Coordination Networks of 3,3'-Dicyanodiphenylacetylene and Silver(I) Salts: Structural Diversity through Changes in Ligand Conformation and Counterion.

Coordination networks of 3,3'-dicyanodiphenylacetylene (3,3'-DCPA, 1) with silver(I) salts characterized by single-crystal X-ray analysis are described. Network topology is found to depend on both the counterion and solvent employed during crystallization. The conformation adopted by the ligand varies between planar cisoid and planar transoid. With silver(I) triflate (AgCF(3)SO(3)) in benzene, a sheet structure of composition [Ag(1)CF(3)SO(3)]C(6)H(6) (2) forms in which silver(I) is five-coordinate and bonds to two nitrogen atoms of distinct 3,3'-DCPA molecules, another silver(I) ion, and two oxygen atoms of the triflate ions. Changing the solvent to toluene produces an undulating sheet structure of composition [Ag(2)(1)(CF(3)SO(3))(2)] (3) in which silver(I) is six-coordinate, bonding to a ligand nitrogen atom, to four oxygen atoms of bridging triflate ions, and to a neighboring silver(I) ion. In both triflate structures, 3,3'-DCPA adopts a transoid conformation with respect to the positioning of the nitrile groups. With silver(I) hexafluorophosphate (AgPF(6)), silver(I) hexafluoroarsenate (AgAsF(6)), or silver(I) hexafluoroantimonate (AgSbF(6)), 2-fold interpenetrated sheet structures [Ag(1)(2)]XF(6) (X = P (4), As (5), or Sb (6)) are obtained in which 3,3'-DCPA coordinates to tetrahedral silver(I) ions in a cisoid conformation. In spite of the large difference in counterion size, minimal network deformation is observed among these systems. Interestingly, with silver(I) perchlorate hydrate (AgClO(4).xH(2)O, x approximately 1), 3,3'-DCPA coordinates in a transoid conformation to tetrahedral silver(I) ions to form the 8-fold interpenetrated diamondoid network [Ag(1)(2)]ClO(4).H(2)O (7). An analysis of the packing of these networks is provided, and the results are compared to complementary systems previously reported from our study of coordination networks of dinitriles and silver(I) salts.

Molecular structure of {[Ag 13(μ-SC 5H 9NHMe) 16] 13+} n, a novel one-dimensional non-molecular silver-thiolate

The polymeric structure of the {[Ag 13(μ-SC 5H 9NHMe) 16] 13+} n cation contains Ag 10S 16 units linked by three silver atoms. Each unit consists of a central Ag 6(μ-SR) 6 core and two Ag 4(μ-SR) 4 rings, and comprises digonal, trigonal and tetrahedral silver and doubly- and triply-bridging sulphur atoms.

ChemInform Abstract: Stable, Chelated, Tetrahedral Silver(I) Complexes with Bidentate Phosphine Ligands.

ChemInform Abstract: Stable, Chelated, Tetrahedral Silver(I) Complexes with Bidentate Phosphine Ligands.

Correlation between metal NMR physical quantities and structures of metal complexes. I. 109Ag NMR spectroscopy of aqueous silver ions coordinated with nitroxide radical

Experimental 109Ag NMR and theoretical MO methods have been used to investigate the electronic structure of silver complexes in aqueous solution. 109Ag spectra of ionic silver solutions (⩽1.0 M) can be obtained with a short repetition time (2–3 s) when 0.020 M 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl is added as a doping agent. By consideration of multiple equilibria, 109Ag chemical shifts of silver complexes in aqueous solution were found to cover a range of 0 to 1300 ppm, relative to 1.0 M AgNO 3. Tetrahedral silver complexes were at lowest field with linear silver complexes more shielded and hydrated silver ion at highest field. Our study suggests a correlation between 109Ag chemical shielding and the structure of silver complexes in aqueous solution. An ab initio SCF MO method using a STO-3G basis set is used to clarify the nature of the ligand-silver interaction and to interprete the observed 109Ag chemical shifts. The results indicate that electron density transfers from the lone pair of the ligand to vacant 5s and 5p orbitals on silver. Also back donation to ligand produces a hole in the 4d orbitals coincident with the bonding axes of silver complexes. The 109Ag chemical shieldings are found to be explained by the paramagnetic term, which depends upon p electrons and d holes on the Ag atom according to qualitative perturbation theory.

Copper(I) and silver(I) ions in unusual poly donor-atom environments; X-ray crystal and molecular structures of [M{( R)( S)-1,2-(5-Me-thiophene-2-CHz.dbnd;N) 2-cyclohexane} 2](O 3SCF 3), M = Cu I or Ag I

Coordination properties of 0.t’ and Cu’ with ligand systems containing N and S donor atoms as potential coordinating sites continue to be of interest as models for the redox active sites in the ‘blue’ proteins [ 1] . The conformation and rigidity of the carbon skeleton connecting the hetero-atoms, as well as the types and number of hetero-atoms in the model ligand systems, are important with respect to both the number of metal atoms which can be bonded and the ultimate configuration at the metal centres. Recently we have shown that the quadridentate N-donor ligands (R)(S)-1 ,2-(6-R-py-2-CH=N)Z-cyclohexane (R = H or Me), in which the inner two N-donor sites are connected by the (R)(S)-1,2cyclohexanediyl ring, act as di-bidentate ligands binding two Cur or Ag’ atoms (see Fig. 1) [2]. The application of INEPT “N and ro9Ag NMR spectroscopy revealed that the structural features found for the silver(I) complex [Ag,{(R@)-1,2(py-2-CH=N)z-cyclohexane),l(03SCF3)2 in the solid, with characteristic alternating two short and two long Ag-N distances around the distorted tetrahedral silver centres [2], are retained in solution [3] . Attempts to form mononuclear Cu’ or Ag’ complexes with these N4donor ligands, using ‘A Curor Agr-to-ligand ratios were unsuccessful. Interpretation of these results requires more information concerning the influence of the donor sites on the coordination properties of these types of potentially quadridentate ligands. For this purpose we have now investigated the bonding features of the N2S, ligand system (R)(S)-1,2-(5-R-thiophene-