Crystallization of Keggin-Type Polyaluminum Species by Supramolecular Interactions with Disulfonate Anions

The hydrolysis of aluminum and formation of polynuclear species, such as the Keggin-type polycations, impacts the chemical and physical properties of the resulting aluminum oxide and hydroxide materials. Despite years of study, only a handful of Keggin-type species have been identified, hampering efforts toward a molecular-level understanding of the mechanisms of condensation. To improve the crystallization of Keggin-type polyaluminum cations, a supramolecular approach using 2,6-napthalene disulfonate (2,6-NDS) was proposed herein for the isolation of novel compounds. The present study describes the successful synthesis and structural characterization of three Keggin-type polyaluminum compounds, including (Na­(Al­(μ₄-O₄)­Al₁₂(μ-OH)₂₄(H₂O))₁₂(2,6NDS)₄(H2O)_13.5 (δ-Al₁₃), (Al₂(μ₄-O₈)­(Al₂₈(μ₂-OH)₅₆(H₂O)₂₆)­(2,6NDS)₈Cl₂(H₂O)₄₀ (Al₃₀), and a new polycation, (Al₂(μ₄-O₈)­(Al₂₄(μ₂-OH)₅₀(H₂O)₂₀)­(2,6NDS)₆(H₂O)_12.4 (Al₂₆). Additional chemical characterization of the compounds, particularly ²⁷Al-NMR, suggests that identifying the Al₂₆ polycation in aqueous solutions may be difficult due to structural similarities to the δ-Al₁₃ moiety. The structural characterization of novel Keggin-type aluminum polycations is important for a complete understanding of aluminum hydrolysis in aqueous solutions, and organosulfonates represent a viable approach for the crystallization of new polynuclear species

Surface Modification of Al₃₀ Keggin-Type Polyaluminum Molecular Clusters

Keggin-type molecular clusters formed from the partial hydrolysis of aluminum in aqueous solutions have the capacity to adsorb a variety of inorganic and organic contaminants. The adsorptive capability of Keggin-type polyaluminum species, such as Al₁₃ and Al₃₀, lead to their wide usage as precursors for heterogeneous catalysts and clarifying agents for water purification applications, but a molecular-level understanding of adsorption process is lacking. Two model Al₃₀ clusters, whose surface has been modified with chelated metals (Al³⁺ and Zn²⁺) have been synthesized and structurally characterized by single-crystal X-ray diffraction. <b>Al</b>_<b>32</b><b>IDA</b> [(Al­(IDA)­H₂O)₂­(Al₃₀O₈(OH)₆₀­(H₂O)₂₂)]­(2,6-NDS)₄­(SO₄)_2­Cl₄­(H₂O)₄₀, IDA = iminodiacetic acid, 2,6-NDS = 2,6 napthalene disulfonate) crystallize in the triclinic space group, <i>P</i>1̅ with <i>a</i> = 13.952(2) Å, <i>b</i> = 16.319(3) Å, <i>c</i> = 23.056(4) Å, α = 93.31(1)°, β = 105.27(1)°, and γ = 105.52(1)°. <b>Zn</b>_<b>2</b><b>Al</b>_<b>32</b> [(Zn­(NTA)­H₂O)₂­(Al­(NTA)­(OH)₂)₂­(Al₃₀(OH)₆₀(O)₈­(H₂O)₂₀]­(2,6-NDS)₅­(H₂O)₆₄, (NTA = nitrilotriacetic acid), also crystallizes in <i>P</i>1̅ with unit cell parameter refined as <i>a</i> = 16.733(7) Å, <i>b</i> = 18.034(10) Å, <i>c</i> = 21.925(11) Å, α = 82.82(2)°, β = 70.96(2)°, and γ = 65.36(2)°. The chelated metal centers adsorb to the surface of the Al₃₀ clusters through hydroxyl bridges located at the central belt region of the molecule. The observed binding sites for the metal centers mirror the reactivity predicted by previously reported molecular dynamic simulations and can be identified by the acidity and hydration factor of the water group that participates in the adsorption process

Design, Synthesis, and Structural Characterization of a Bisantimony(III) Compound for Anion Binding and the Density Functional Theory Evaluation of Halide Binding through Antimony Secondary Bonding Interactions

Density functional theory calculations were used to design an anion receptor that utilizes antimony­(III) secondary bonding interactions. Calculations were performed on promising motifs found in the chemical literature where two antimony sites were found in close proximity to a halide anion. The study was extended to a structurally related class of 1,3,2-benzodioxastibole derivatives to elucidate their potential for binding halide ions. Multiple geometric conformations were evaluated and various ratios of halide anions were considered. According to the computation results, this class of anion receptors shows strong affinities toward charge-dense halides. These 1,3,2-benzodioxastibole derivatives were prepared to evaluate their synthetic accessibility. Structural characterization of one species revealed the ability to bind up to three electron donors through secondary bonding interactions. This gates the future experimental study of these antimony systems for anion binding and recognition

Crystallization of Keggin-Type Polyaluminum Species by Supramolecular Interactions with Disulfonate Anions

The hydrolysis of aluminum and formation of polynuclear species, such as the Keggin-type polycations, impacts the chemical and physical properties of the resulting aluminum oxide and hydroxide materials. Despite years of study, only a handful of Keggin-type species have been identified, hampering efforts toward a molecular-level understanding of the mechanisms of condensation. To improve the crystallization of Keggin-type polyaluminum cations, a supramolecular approach using 2,6-napthalene disulfonate (2,6-NDS) was proposed herein for the isolation of novel compounds. The present study describes the successful synthesis and structural characterization of three Keggin-type polyaluminum compounds, including (Na­(Al­(μ₄-O₄)­Al₁₂(μ-OH)₂₄(H₂O))₁₂(2,6NDS)₄(H2O)_13.5 (δ-Al₁₃), (Al₂(μ₄-O₈)­(Al₂₈(μ₂-OH)₅₆(H₂O)₂₆)­(2,6NDS)₈Cl₂(H₂O)₄₀ (Al₃₀), and a new polycation, (Al₂(μ₄-O₈)­(Al₂₄(μ₂-OH)₅₀(H₂O)₂₀)­(2,6NDS)₆(H₂O)_12.4 (Al₂₆). Additional chemical characterization of the compounds, particularly ²⁷Al-NMR, suggests that identifying the Al₂₆ polycation in aqueous solutions may be difficult due to structural similarities to the δ-Al₁₃ moiety. The structural characterization of novel Keggin-type aluminum polycations is important for a complete understanding of aluminum hydrolysis in aqueous solutions, and organosulfonates represent a viable approach for the crystallization of new polynuclear species

Crystallization of Keggin-Type Polyaluminum Species by Supramolecular Interactions with Disulfonate Anions

The hydrolysis of aluminum and formation of polynuclear species, such as the Keggin-type polycations, impacts the chemical and physical properties of the resulting aluminum oxide and hydroxide materials. Despite years of study, only a handful of Keggin-type species have been identified, hampering efforts toward a molecular-level understanding of the mechanisms of condensation. To improve the crystallization of Keggin-type polyaluminum cations, a supramolecular approach using 2,6-napthalene disulfonate (2,6-NDS) was proposed herein for the isolation of novel compounds. The present study describes the successful synthesis and structural characterization of three Keggin-type polyaluminum compounds, including (Na­(Al­(μ₄-O₄)­Al₁₂(μ-OH)₂₄(H₂O))₁₂(2,6NDS)₄(H2O)_13.5 (δ-Al₁₃), (Al₂(μ₄-O₈)­(Al₂₈(μ₂-OH)₅₆(H₂O)₂₆)­(2,6NDS)₈Cl₂(H₂O)₄₀ (Al₃₀), and a new polycation, (Al₂(μ₄-O₈)­(Al₂₄(μ₂-OH)₅₀(H₂O)₂₀)­(2,6NDS)₆(H₂O)_12.4 (Al₂₆). Additional chemical characterization of the compounds, particularly ²⁷Al-NMR, suggests that identifying the Al₂₆ polycation in aqueous solutions may be difficult due to structural similarities to the δ-Al₁₃ moiety. The structural characterization of novel Keggin-type aluminum polycations is important for a complete understanding of aluminum hydrolysis in aqueous solutions, and organosulfonates represent a viable approach for the crystallization of new polynuclear species

Surface Modification of Al₃₀ Keggin-Type Polyaluminum Molecular Clusters

Keggin-type molecular clusters formed from the partial hydrolysis of aluminum in aqueous solutions have the capacity to adsorb a variety of inorganic and organic contaminants. The adsorptive capability of Keggin-type polyaluminum species, such as Al₁₃ and Al₃₀, lead to their wide usage as precursors for heterogeneous catalysts and clarifying agents for water purification applications, but a molecular-level understanding of adsorption process is lacking. Two model Al₃₀ clusters, whose surface has been modified with chelated metals (Al³⁺ and Zn²⁺) have been synthesized and structurally characterized by single-crystal X-ray diffraction. <b>Al</b>_<b>32</b><b>IDA</b> [(Al­(IDA)­H₂O)₂­(Al₃₀O₈(OH)₆₀­(H₂O)₂₂)]­(2,6-NDS)₄­(SO₄)_2­Cl₄­(H₂O)₄₀, IDA = iminodiacetic acid, 2,6-NDS = 2,6 napthalene disulfonate) crystallize in the triclinic space group, <i>P</i>1̅ with <i>a</i> = 13.952(2) Å, <i>b</i> = 16.319(3) Å, <i>c</i> = 23.056(4) Å, α = 93.31(1)°, β = 105.27(1)°, and γ = 105.52(1)°. <b>Zn</b>_<b>2</b><b>Al</b>_<b>32</b> [(Zn­(NTA)­H₂O)₂­(Al­(NTA)­(OH)₂)₂­(Al₃₀(OH)₆₀(O)₈­(H₂O)₂₀]­(2,6-NDS)₅­(H₂O)₆₄, (NTA = nitrilotriacetic acid), also crystallizes in <i>P</i>1̅ with unit cell parameter refined as <i>a</i> = 16.733(7) Å, <i>b</i> = 18.034(10) Å, <i>c</i> = 21.925(11) Å, α = 82.82(2)°, β = 70.96(2)°, and γ = 65.36(2)°. The chelated metal centers adsorb to the surface of the Al₃₀ clusters through hydroxyl bridges located at the central belt region of the molecule. The observed binding sites for the metal centers mirror the reactivity predicted by previously reported molecular dynamic simulations and can be identified by the acidity and hydration factor of the water group that participates in the adsorption process

Surface Modification of Al₃₀ Keggin-Type Polyaluminum Molecular Clusters

Keggin-type molecular clusters formed from the partial hydrolysis of aluminum in aqueous solutions have the capacity to adsorb a variety of inorganic and organic contaminants. The adsorptive capability of Keggin-type polyaluminum species, such as Al₁₃ and Al₃₀, lead to their wide usage as precursors for heterogeneous catalysts and clarifying agents for water purification applications, but a molecular-level understanding of adsorption process is lacking. Two model Al₃₀ clusters, whose surface has been modified with chelated metals (Al³⁺ and Zn²⁺) have been synthesized and structurally characterized by single-crystal X-ray diffraction. <b>Al</b>_<b>32</b><b>IDA</b> [(Al­(IDA)­H₂O)₂­(Al₃₀O₈(OH)₆₀­(H₂O)₂₂)]­(2,6-NDS)₄­(SO₄)_2­Cl₄­(H₂O)₄₀, IDA = iminodiacetic acid, 2,6-NDS = 2,6 napthalene disulfonate) crystallize in the triclinic space group, <i>P</i>1̅ with <i>a</i> = 13.952(2) Å, <i>b</i> = 16.319(3) Å, <i>c</i> = 23.056(4) Å, α = 93.31(1)°, β = 105.27(1)°, and γ = 105.52(1)°. <b>Zn</b>_<b>2</b><b>Al</b>_<b>32</b> [(Zn­(NTA)­H₂O)₂­(Al­(NTA)­(OH)₂)₂­(Al₃₀(OH)₆₀(O)₈­(H₂O)₂₀]­(2,6-NDS)₅­(H₂O)₆₄, (NTA = nitrilotriacetic acid), also crystallizes in <i>P</i>1̅ with unit cell parameter refined as <i>a</i> = 16.733(7) Å, <i>b</i> = 18.034(10) Å, <i>c</i> = 21.925(11) Å, α = 82.82(2)°, β = 70.96(2)°, and γ = 65.36(2)°. The chelated metal centers adsorb to the surface of the Al₃₀ clusters through hydroxyl bridges located at the central belt region of the molecule. The observed binding sites for the metal centers mirror the reactivity predicted by previously reported molecular dynamic simulations and can be identified by the acidity and hydration factor of the water group that participates in the adsorption process

Nickel-Catalyzed Regioselective 1,4-Hydroboration of N‑Heteroarenes

Combinations of Ni­(acac)₂ with phosphine ligands were found to catalyze the regioselective hydroboration of N-heteroarenes with pinacolborane, affording <i>N</i>-borylated 1,4-reduction products. Preliminary mechanistic studies have focused on the isolation and study of potential intermediates in the catalytic cycle

Competitive Pseudopericyclic [3,3]- and [3,5]-Sigmatropic Rearrangements of Trichloroacetimidates

The Woodward–Hoffmann rules predict whether concerted pericyclic reactions are allowed or forbidden based on the number of electrons involved and whether the cyclic orbital overlap involves suprafacial or antarafacial orbital overlap. Pseudopericyclic reactions constitute a third class of reactions in which orthogonal orbitals make them orbital symmetry allowed, regardless of the number of electrons involved in the reaction. Based on the recent report of eight-centered ester rearrangements, it is predicted that the isoelectronic eight-centered rearrangements of imidates would also be allowed. We now report that these rearrangements occur, and indeed, an eight-centered rearrangement is slightly favored in at least one case over the well-known six-centered Overman rearrangements, in a trichloroacetimidoylcyclohexadienone, a molecular system where both rearrangements are possible

Synthesis and Structural Characterization of Heterometallic Thorium Aluminum Polynuclear Molecular Clusters

Aluminum can undergo hydrolysis in aqueous solutions leading to the formation of soluble molecular clusters, including polynuclear species that range from 1 to 2 nm in diameter. While the behavior of aluminum has been extensively investigated, much less is known about the hydrolysis of more complex mixed-metal systems. This study focuses on the structural characteristics of heterometallic thorium–aluminum molecular species that may have important implications for the speciation of tetravalent actinides in radioactive waste streams and environmental systems. Two mixed metal (Th⁴⁺/Al³⁺) polynuclear species have been synthesized under ambient conditions and structurally characterized by single-crystal X-ray diffraction. [Th₂Al₆(OH)₁₄(H₂O)₁₂(hedta)₂]­(NO₃)₆(H₂O)₁₂ (<b>ThAl1</b>) crystallizes in space group <i>P</i>2₁/<i>c</i> with unit cell parameters of <i>a</i> = 11.198(1) Å, <i>b</i> = 14.210(2) Å, <i>c</i> = 23.115(3) Å, and β = 96.375° and [Th₂Al₈(OH)₁₂(H₂O)₁₀(hdpta)₄]­(H₂O)₂₁ (<b>ThAl2</b>) was modeled in <i>P</i>1̅ with <i>a</i> = 13.136(4) Å, <i>b</i> = 14.481(4) Å, <i>c</i> = 15.819(4) Å, α = 78.480(9)°, β = 65.666(8)°, γ = 78.272(8)°. Infrared spectra were collected on both compounds, confirming complexation of the ligand to the metal center, and thermogravimetric analysis indicated that the thermal degradation of these compounds resulted in the formation of an amorphous product at high temperatures. These mixed metal species have topological relationships to previously characterized aluminum-based polynuclear species and may provide insights into the adsorption of tetravalent actinides on colloidal or mineral surfaces