Diverse intermolecular interactions in silver(I)-organic frameworks constructed with flexible supramolecular synthons

Elusive Coordination of the Ag+ Ion in Aqueous Solution: Evidence for a Linear Structure

X-ray absorption spectroscopy (XAS) has been employed to study the coordination of the Ag⁺ ion in aqueous solution. The conjunction of extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) data analysis provided results suggesting the preference for a first shell linear coordination with a mean Ag-O bond distance of 2.34(2) Å, different from the first generally accepted tetrahedral model with a longer mean Ag-O bond distance. Ab initio molecular dynamics simulations with the Car-Parrinello approach (CPMD) were also performed and were able to describe the coordination of the hydrated Ag⁺ ion in aqueous solution in very good agreement with the experimental data. The high sensitivity for the closest environment of the photoabsorber of the EXAFS and XANES techniques, together with the long-range information provided by CPMD and large-angle X-ray scattering (LAXS), allowed us to reconstruct the three-dimensional model of the coordination geometry around the Ag⁺ ion in aqueous solution. The obtained results from experiments and theoretical simulations provided a complex picture with a certain amount of water molecules with high configurational disorder at distances comprised between the first and second hydration spheres. This evidence may have caused the proliferation of the coordination numbers that have been proposed so far for Ag⁺ in water. Altogether these data show how the description of the hydration of the Ag⁺ ion in aqueous solution can be complex, differently from other metal species where hydration structures can be described by clusters with well-defined geometries. This diffuse hydration shell causes the Ag-O bond distance in the linear [Ag(H₂O)₂]⁺ ion to be ca. 0.2 Å longer than in isolated ions in solid state.

Comprehensive Theoretical Study of Interactions between Ag+ and Polycyclic Aromatic Hydrocarbons

The first comprehensive and systematic theoretical exploration of the bonding nature and energetics of the interactions between Ag(I) cation and a wide set of π-ligands was accomplished. This set ranges from simple ethylene and aromatic benzene to planar and curved polyaromatic molecules and to closed-cage C₆₀ -fullerene. Simultaneous application of two energy decomposition schemes based on different ideas, namely, NBO-NEDA and EDA-NOCV, allowed shedding light on the nature of the bonding and its energetics. Importantly, our results unambiguously indicate that reliable results can be obtained only if using more than one theoretical approach. All methods clearly revealed the importance and even domination of the ionic contribution of the bonding in all adducts, except for those of C₆₀ -fullerene, in which the covalent component was found to be the largest. Subsequent decomposition of the orbital term onto components showed that it consists of two major parts: (i) ligand-to-metal (π(C=C)→s(Ag), L→M) and (ii) metal-to-ligand (M→L) terms, with significant domination of the former. Interestingly, while the L→M component is essentially the same for all systems considered, the nature of the M→L one depends on the coordination site of the polycyclic aromatic hydrocarbons (PAH). In most of adducts, the M→L can be described as d_xy (Ag)→π^* (C=C) donation, whereas for systems [Ag-spoke-C₁₂ H₈ ]⁺ and [Ag-spoke-C₂₀ H₁₀ ]⁺ it corresponds to the d_z ² (Ag)→π^* (C=C) type of interaction. As a result, the coordination mode in such complexes is switched from η² -type to η¹ . Thus, the nature of the bonding, its energetics and even coordination mode in adducts of unsaturated hydrocarbons with late transition metal cations should be considered as a function of many components, which primarily includes the topology and aromaticity of the (poly)aromatic molecules.

Copper-catalyzed, silver-mediated formal [3+2] cycloaddition of simple alkynes with β-ketoesters through propargylic C(sp3)–H functionalization

The propargylic C(sp³)–H functionalization strategy has been successfully employed in the copper-catalyzed [3+2] cycloaddition of simple alkynes with β-ketoesters. Under optimal conditions, the reaction proceeds smoothly to give a variety of highly functionalized furans in moderate to high yields.

Crystal structures of [SbF6]− salts of di- and tetrahydrated Ag +, tetrahydrated Pd2 + and hexahydrated Cd2 + cations

The [Ag(H2O)2]SbF6, is triclinic, P1̅ (No. 2), with a=6.6419(3) Å, b=7.6327(3) Å, c=11.1338(3) Å, α=95.492(3)°, β=96.994(3)°, γ=113.535(4)°, V=507.13(4) Å3 at 150 K, and Z=3. There are two crystallographically non-equivalent Ag+ cations. The Ag1 is coordinated by two water molecules with Ag–OH2 distances equal to 2.271(2) Å forming in that way a discrete linear [Ag(H2O)2]+ cation. Additionaly, it forms two short Ag···F contacts (2.630(2) Å), resulting in AgO2F2 plaquette, and four long ones (2×3.001(2) Å and 2×3.095(2) Å) with fluorine atoms located below and above the AgO2F2 plaquette. The H2O molecules bridge Ag2 atoms into {–[Ag(μ-OH2)2]–}n infinite chains, with Ag–O distances of 2.367(2)–2.466(2) Å. The [Pd(H2O)4](SbF6)2·4H2O is monoclinic, P2 1 /a (No.14), with a=8.172(2) Å, b=13.202(3) Å, c=8.188(3) Å, β=115.10(1)o, V=799.9(4) Å3 at 200 K, and Z=2. Its crystal structure can be described as an alternation of layers of [Pd(H2O)4]2+ cations (interconnected by H2O molecules) and [SbF6]− anions. It represents the first example where [Pd(H2O)4]2+ has been structurally determined in the solid state. Four oxygen atoms provided by H2O molecules are in almost ideal square-planar arrangement with Pd–O bond lengths 2×2.004(5) Å and 2×2.022(6) Å. The [Cd(H2O)6](SbF6)2, is orthorhombic, Pnnm (No.58), with a=5.5331(2) Å, b=14.5206(4) Å, c=8.9051(3) Å, V=715.47(4) Å3 at 200 K, and Z=2. It consists of [Cd(H2O)6]2+ cations and [SbF6]− anions.

Arenediazonium salts as electrophiles for the oxidative addition of gold(i)

Arenediazonium salts have been found to behave as efficient electrophiles for the oxidation of gold(i). Starting from anilines, a one pot cross-coupling reaction of anilines with silver acetylides mediated by gold has been developed.

Diverse silver(i) sulfobenzoate coordination polymers and their recycling property as homogeneous catalyst in oxygenation of sulfide

Four silver sulfobenzoate coordination polymers with bpmb ligands were prepared. The variable positions of sulfonate groups on benzene rings gave rise to different coordination polymers and variable chemical properties.

Synthesis, characterization, crystal structures and thermal and photoluminescence studies of dimethylpyrazine-carboxylate mixed ligand silver(i) coordination polymers with various multinuclear silver units

Seven new silver(i) coordination compounds based on dimethylpyrazine have been synthesized and characterized.