Organoarsonate Functionalization of Heteropolyoxotungstates

Functionalization of the {P₈W₄₈} polyoxotungstate (POT) archetype with aromatic organoarsonates results in the first homometallic {P₈W₄₈} derivatives, with the general formula [(RAs^VO)₄P^V₈W^VI₄₈O₁₈₄]³²⁻ [R = C₆H₅ (<b>1</b>) or <i>p</i>-(H₂N)­C₆H₄ (<b>2</b>)]. Short As−O bonds here induce unusual bending of the otherwise rigid {P₈W₄₈} macrocycle, breaking its <i>D</i>_4<i>h</i> symmetry. The obtained species also represent the first lacunary POTs functionalized with organoarsonates and can potentially act as polyoxometalate precursors themselves. We elaborate solution stability in different aqueous media using ¹H and ³¹P NMR spectroscopy and possible pathways for subsequent transformations in aqueous solutions of the functionalized polyanions. Recrystallization of the K⁺/Li⁺/dimethylammonium salt of <b>2</b> from 4 M LiCl solution yielded a further functionalized POT, [(H₃NC₆H₄AsO)₃P₈W₄₈O₁₈₄H_<i>x</i>{WO₂(H₂O)₂}_0.4]^{(30.2−<i>x</i>)−} (<b>3</b>), revealing dissociation of the organoarsonate fragments in slightly acidic aqueous solutions followed by their rearrangement within the inner POT cavity

Expansion of Antimonato Polyoxovanadates with Transition Metal Complexes: (Co(N₃C₅H₁₅)₂)₂[{Co(N₃C₅H₁₅)₂}V₁₅Sb₆O₄₂(H₂O)]·5H₂O and (Ni(N₃C₅H₁₅)₂)₂[{Ni(N₃C₅H₁₅)₂}V₁₅Sb₆O₄₂(H₂O)]·8H₂O

Two new polyoxovanadates (Co­(N₃C₅H₁₅)₂)₂[{Co­(N₃C₅H₁₅)₂}­V₁₅Sb₆O₄₂(H₂O)]·5H₂O (<b>1</b>) and (Ni­(N₃C₅H₁₅)₂)₂[{Ni­(N₃C₅H₁₅)₂}­V₁₅Sb₆O₄₂(H₂O)]·8H₂O (<b>2</b>) (N₃C₅H₁₅ = <i>N</i>-(2-aminoethyl)-1,3-propanediamine) were synthesized under solvothermal conditions and structurally characterized. In both structures the [V₁₅Sb₆O₄₂(H₂O)]^6– shell displays the main structural motif, which is strongly related to the {V₁₈O₄₂} archetype cluster. Both compounds crystallize in the triclinic space group <i>P</i>1̅ with <i>a</i> = 14.3438(4), <i>b</i> = 16.6471(6), <i>c</i> = 18.9186(6) Å, α = 87.291(3)°, β = 83.340(3)°, γ = 78.890(3)°, and <i>V</i> = 4401.4(2) ų (<b>1</b>) and <i>a</i> = 14.5697(13), <i>b</i> = 15.8523(16), <i>c</i> = 20.2411(18) Å, α = 86.702(11)°, β = 84.957(11)°, γ = 76.941(11)°, and <i>V</i> = 4533.0(7) ų (<b>2</b>). In the structure of <b>1</b> the [V₁₅Sb₆O₄₂(H₂O)]^6– cluster anion is bound to a [Co­(N₃C₅H₁₅)₂]²⁺ complex via a terminal oxygen atom. In the Co²⁺-centered complex, one of the amine ligands coordinates in tridentate mode and the second one in bidentate mode to form a strongly distorted CoN₅O octahedron. Similarly, in compound <b>2</b> an analogous NiN₅O complex is joined to the [V₁₅Sb₆O₄₂(H₂O)]^6– anion via the same attachment mode. A remarkable difference between the two compounds is the orientation of the noncoordinated propylamine group leading to intermolecular Sb···O contacts in <b>1</b> and to Sb···N interactions in <b>2</b>. In the solid-state lattices of <b>1</b> and <b>2</b>, two additional [M­(N₃C₅H₁₅)₂]²⁺ complexes act as countercations and are located between the [{M­(N₃C₅H₁₅)₂}­V₁₅Sb₆O₄₂(H₂O)]^4– anions. Between the anions and cations strong N–H···O hydrogen bonds are observed. In both compounds the clusters are stacked along the <i>b</i> axis in an ABAB fashion with cations and water molecules occupying the space between the clusters. Magnetic characterization demonstrates that the Ni²⁺ and Co²⁺ cations do not significantly couple with the <i>S</i> = 1/2 vanadyl groups. The susceptibility data can be successfully reproduced assuming a distorted ligand field for the Co²⁺ ions (<b>1</b>) and an <i>O</i>_<i>h</i>-symmetric Ni²⁺ ligand field (<b>2</b>)

Chiral Hexanuclear Ferric Wheels

The homochiral iron­(III) wheels [Fe₆{(<i>S</i>)-pedea}₆Cl₆] and [Fe₆{(<i>R</i>)-pedea)}₆Cl₆] [(<i>R</i>)- and (<i>S</i>)-<b>2</b>; pedea = phenylethylaminodiethoxide] exhibit high optical activities and antiferromagnetic exchange. These homochiral products react with each other, producing the centrosymmetric, crystallographically characterized [Fe₆{(<i>S</i>)-pedea}₃{(<i>R</i>)-pedea}₃Cl₆] diastereomer [(<i>RSRSRS</i>)-<b>2</b>]. ¹H NMR and UV–vis studies indicate that exchange processes are slow in both homo- and heterochiral systems but that, upon combination, the reaction between (<i>R</i>)- and (<i>S</i>)-<b>2</b> occurs quickly

Expansion of Antimonato Polyoxovanadates with Transition Metal Complexes: (Co(N₃C₅H₁₅)₂)₂[{Co(N₃C₅H₁₅)₂}V₁₅Sb₆O₄₂(H₂O)]·5H₂O and (Ni(N₃C₅H₁₅)₂)₂[{Ni(N₃C₅H₁₅)₂}V₁₅Sb₆O₄₂(H₂O)]·8H₂O

Two new polyoxovanadates (Co­(N₃C₅H₁₅)₂)₂[{Co­(N₃C₅H₁₅)₂}­V₁₅Sb₆O₄₂(H₂O)]·5H₂O (<b>1</b>) and (Ni­(N₃C₅H₁₅)₂)₂[{Ni­(N₃C₅H₁₅)₂}­V₁₅Sb₆O₄₂(H₂O)]·8H₂O (<b>2</b>) (N₃C₅H₁₅ = <i>N</i>-(2-aminoethyl)-1,3-propanediamine) were synthesized under solvothermal conditions and structurally characterized. In both structures the [V₁₅Sb₆O₄₂(H₂O)]^6– shell displays the main structural motif, which is strongly related to the {V₁₈O₄₂} archetype cluster. Both compounds crystallize in the triclinic space group <i>P</i>1̅ with <i>a</i> = 14.3438(4), <i>b</i> = 16.6471(6), <i>c</i> = 18.9186(6) Å, α = 87.291(3)°, β = 83.340(3)°, γ = 78.890(3)°, and <i>V</i> = 4401.4(2) ų (<b>1</b>) and <i>a</i> = 14.5697(13), <i>b</i> = 15.8523(16), <i>c</i> = 20.2411(18) Å, α = 86.702(11)°, β = 84.957(11)°, γ = 76.941(11)°, and <i>V</i> = 4533.0(7) ų (<b>2</b>). In the structure of <b>1</b> the [V₁₅Sb₆O₄₂(H₂O)]^6– cluster anion is bound to a [Co­(N₃C₅H₁₅)₂]²⁺ complex via a terminal oxygen atom. In the Co²⁺-centered complex, one of the amine ligands coordinates in tridentate mode and the second one in bidentate mode to form a strongly distorted CoN₅O octahedron. Similarly, in compound <b>2</b> an analogous NiN₅O complex is joined to the [V₁₅Sb₆O₄₂(H₂O)]^6– anion via the same attachment mode. A remarkable difference between the two compounds is the orientation of the noncoordinated propylamine group leading to intermolecular Sb···O contacts in <b>1</b> and to Sb···N interactions in <b>2</b>. In the solid-state lattices of <b>1</b> and <b>2</b>, two additional [M­(N₃C₅H₁₅)₂]²⁺ complexes act as countercations and are located between the [{M­(N₃C₅H₁₅)₂}­V₁₅Sb₆O₄₂(H₂O)]^4– anions. Between the anions and cations strong N–H···O hydrogen bonds are observed. In both compounds the clusters are stacked along the <i>b</i> axis in an ABAB fashion with cations and water molecules occupying the space between the clusters. Magnetic characterization demonstrates that the Ni²⁺ and Co²⁺ cations do not significantly couple with the <i>S</i> = 1/2 vanadyl groups. The susceptibility data can be successfully reproduced assuming a distorted ligand field for the Co²⁺ ions (<b>1</b>) and an <i>O</i>_<i>h</i>-symmetric Ni²⁺ ligand field (<b>2</b>)

Tetrapalladium-Containing Polyoxotungstate [Pd^II₄(α‑P₂W₁₅O₅₆)₂]^16–: A Comparative Study

The novel tetrapalladium­(II)-containing polyoxometalate [Pd^II₄(<i>α-</i>P₂W₁₅O₅₆)₂]^16– has been prepared in aqueous medium and characterized as its hydrated sodium salt Na₁₆[Pd₄(α-P₂W₁₅O₅₆)₂]·71H₂O by single-crystal XRD, elemental analysis, IR, Raman, multinuclear NMR, and UV–vis spectroscopy. The complex exists in anti and syn conformations, which form in a 2:1 ratio, and possesses unique structural characteristics in comparison with known {M₄(P₂W₁₅)₂} species. ³¹P and ¹⁸³W NMR spectroscopy are consistent with the long-term stability of the both isomers in aqueous solutions

Tuning the Condensation Degree of {Fe^III_<i>n</i>} Oxo Clusters via Ligand Metathesis, Temperature, and Solvents

Trinuclear μ₃-oxo-centered iron­(III) isobutyrate clusters readily react with polyalcohol organic ligands under one-pot synthesis conditions. Depending on the ligand, solvent, and temperature, a range of hexa-, dodeca-, and doicosanuclear iron­(III) oxo-hydroxo condensation products, isolated as (mdeaH₃)₂[Fe₆O­(thme)₄Cl₆]·0.5­(MeCN)·0.5­(H₂O) (<b>1</b>), [Fe₁₂O₄(OH)₂(teda)₄(N₃)₄(MeO)₄]­N₃(NO₃)_0.5(MeO)_0.5·2.5­(H₂O) (<b>2</b>), [Fe₁₂O₆(teda)₄Cl₈]·6­(CHCl₃) (<b>3</b>), [Fe₂₂O₁₆(OH)₂(O₂CCHMe₂)₁₈(bdea)₆(EtO)₂(H₂O)₂]·2­(EtOH)·5­(MeCN)·6­(H₂O) (<b>4</b>), and [Fe₂₂O₁₄(OH)₄(O₂CCHMe₂)₁₈(mdea)₆(EtO)₂(H₂O)₂]­(NO₃)₂·EtOH·H₂O (<b>5</b>), where tedaH₄ = <i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>′-tetrakis­(2-hydroxyethyl)­ethylenediamine; thmeH₃ = 1,1,1-tris­(hydroxymethyl)­ethane; mdeaH₂ = <i>N</i>-methyldiethanolamine; and bdeaH₂ = <i>N</i>-butyldiethanolamine. Complete carboxylate metathesis in the {Fe₃} precursor complexes by thme^3– or teda^4– and the agglomeration of the formed species under solvothermal conditions afforded carboxylate-free {Fe₆} product (<b>1</b>) in MeCN/CH₂Cl₂ or {Fe₁₂} complexes (<b>2</b> and <b>3</b>) in MeOH/EtOH and CHCl₃/thf, respectively (thf = tetrahydrofuran). Single-crystal X-ray diffraction analyses revealed that <b>1</b> contains a [Fe₆O­(thme)₄Cl₆]^2– cluster anion with a Lindqvist-type {Fe₆(μ₆-O)} core motif, charge-compensated by two protonated mdeaH₃⁺ cations. <b>2</b> comprises a [Fe₁₂O₄(OH)₂(teda)₄­(N₃)₄(MeO)₄]²⁺ cation with a {Fe₁₂O₄(OH)₂}²⁶⁺ core, whereas <b>3</b> contains a charge-neutral [Fe₁₂O₆(teda)₄(Cl)₈] complex with an {Fe₁₂O₆}²⁴⁺ core. Finally, employing flexible bdeaH₂ or mdeaH₂ ligands under soft reaction conditions afforded giant {Fe₂₂} oxo-hydroxo complexes (<b>4</b> and <b>5</b>) with a central {Fe₆} layer sandwiched between two outer {Fe₈} groups. Magnetic studies of <b>1</b>–<b>5</b> revealed strong antiferromagnetic coupling between the Fe^III spin centers in all clusters

Synthesis, Structure, and Magnetic Properties of a New Family of Tetra-nuclear {Mn₂^IIILn₂}(Ln = Dy, Gd, Tb, Ho) Clusters With an Arch-Type Topology: Single-Molecule Magnetism Behavior in the Dysprosium and Terbium Analogues

Sequential reaction of Mn­(II) and lanthanide­(III) salts with a new multidentate ligand, 2,2′-(2-hydroxy-3-methoxy-5-methylbenzylazanediyl)­diethanol (<b>LH</b>_<b>3</b>), containing two flexible ethanolic arms, one phenolic oxygen, and a methoxy group afforded heterometallic tetranuclear complexes [Mn₂Dy₂(LH)₄(μ-OAc)₂]­(NO₃)₂·2CH₃OH·3H₂O (<b>1</b>), [Mn₂Gd₂(LH)₄(μ-OAc)₂]­(NO₃)₂·2CH₃OH·3H₂O (<b>2</b>), [Mn₂Tb₂(LH)₄(μ-OAc)₂]­(NO₃)₂·2H₂O·2CH₃OH·Et₂O (<b>3</b>), and [Mn₂Ho₂(LH)₄(μ-OAc)₂]­Cl₂·5CH₃OH (<b>4</b>). All of these dicationic complexes possess an arch-like structural topology containing a central Mn^III–Ln–Ln–Mn^III core. The two central lanthanide ions are connected via two phenolate oxygen atoms. The remaining ligand manifold assists in linking the central lanthanide ions with the peripheral Mn­(III) ions. Four doubly deprotonated LH^2– chelating ligands are involved in stabilizing the tetranuclear assembly. A magnetochemical analysis reveals that single-ion effects dominate the observed susceptibility data for all compounds, with comparably weak Ln···Ln and very weak Ln···Mn­(III) couplings. The axial, approximately square-antiprismatic coordination environment of the Ln³⁺ ions in <b>1</b>–<b>4</b> causes pronounced zero-field splitting for Tb³⁺, Dy³⁺, and Ho³⁺. For <b>1</b> and <b>3</b>, the onset of a slowing down of the magnetic relaxation was observed at temperatures below approximately 5 K (<b>1</b>) and 13 K (<b>3</b>) in frequency-dependent alternating current (AC) susceptibility measurements, yielding effective relaxation energy barriers of Δ<i>E</i> = 16.8 cm^–1 (<b>1</b>) and 33.8 cm^–1 (<b>3</b>)

Synthesis, Structure, and Magnetic Properties of a New Family of Tetra-nuclear {Mn₂^IIILn₂}(Ln = Dy, Gd, Tb, Ho) Clusters With an Arch-Type Topology: Single-Molecule Magnetism Behavior in the Dysprosium and Terbium Analogues

Sequential reaction of Mn­(II) and lanthanide­(III) salts with a new multidentate ligand, 2,2′-(2-hydroxy-3-methoxy-5-methylbenzylazanediyl)­diethanol (<b>LH</b>_<b>3</b>), containing two flexible ethanolic arms, one phenolic oxygen, and a methoxy group afforded heterometallic tetranuclear complexes [Mn₂Dy₂(LH)₄(μ-OAc)₂]­(NO₃)₂·2CH₃OH·3H₂O (<b>1</b>), [Mn₂Gd₂(LH)₄(μ-OAc)₂]­(NO₃)₂·2CH₃OH·3H₂O (<b>2</b>), [Mn₂Tb₂(LH)₄(μ-OAc)₂]­(NO₃)₂·2H₂O·2CH₃OH·Et₂O (<b>3</b>), and [Mn₂Ho₂(LH)₄(μ-OAc)₂]­Cl₂·5CH₃OH (<b>4</b>). All of these dicationic complexes possess an arch-like structural topology containing a central Mn^III–Ln–Ln–Mn^III core. The two central lanthanide ions are connected via two phenolate oxygen atoms. The remaining ligand manifold assists in linking the central lanthanide ions with the peripheral Mn­(III) ions. Four doubly deprotonated LH^2– chelating ligands are involved in stabilizing the tetranuclear assembly. A magnetochemical analysis reveals that single-ion effects dominate the observed susceptibility data for all compounds, with comparably weak Ln···Ln and very weak Ln···Mn­(III) couplings. The axial, approximately square-antiprismatic coordination environment of the Ln³⁺ ions in <b>1</b>–<b>4</b> causes pronounced zero-field splitting for Tb³⁺, Dy³⁺, and Ho³⁺. For <b>1</b> and <b>3</b>, the onset of a slowing down of the magnetic relaxation was observed at temperatures below approximately 5 K (<b>1</b>) and 13 K (<b>3</b>) in frequency-dependent alternating current (AC) susceptibility measurements, yielding effective relaxation energy barriers of Δ<i>E</i> = 16.8 cm^–1 (<b>1</b>) and 33.8 cm^–1 (<b>3</b>)

Ultralarge 3d/4f Coordination Wheels: From Carboxylate/Amino Alcohol-Supported {Fe₄Ln₂} to {Fe₁₈Ln₆} Rings

A family of wheel-shaped charge-neutral heterometallic {Fe^III₄Ln^III₂}- and {Fe^III₁₈M^III₆}-type coordination clusters demonstrates the intricate interplay of solvent effects and structure-directing roles of semiflexible bridging ligands. The {Fe₄Ln₂}-type compounds [Fe₄Ln₂(O₂CCMe₃)₆­(N₃)₄(Htea)₄]·2­(EtOH), Ln = Dy (<b>1a</b>), Er (<b>1b</b>), Ho (<b>1c</b>); [Fe₄Tb₂(O₂CCMe₃)₆­(N₃)₄(Htea)₄] (<b>1d</b>); [Fe₄Ln₂(O₂CCMe₃)₆­(N₃)₄(Htea)₄]·2­(CH₂Cl₂), Ln = Dy (<b>2a</b>), Er (<b>2b</b>); [Fe₄Ln₂(O₂CCMe₃)₄­(N₃)₆(Htea)₄]·2­(EtOH)·2­(CH₂Cl₂), Ln = Dy (<b>3a</b>), Er (<b>3b</b>) and the {Fe₁₈M₆}-type compounds [Fe₁₈M₆(O₂CCHMe₂)₁₂­(Htea)₁₈(tea)₆(N₃)₆]·<i>n</i>(solvent), M = Dy (<b>4</b>, <b>4a</b>), Gd (<b>5</b>), Tb (<b>6</b>), Ho (<b>7</b>), Sm (<b>8</b>), Eu (<b>9</b>), and Y (<b>10</b>) form in ca. 20–40% yields in direct reaction of trinuclear Fe^III pivalate or isobutyrate clusters, lanthanide/yttrium nitrates, and bridging triethanolamine (H₃tea) and azide ligands in different solvents: EtOH for the smaller {Fe₄Ln₂} wheels and MeOH/MeCN or MeOH/EtOH for the larger {Fe₁₈M₆} wheels. Single-crystal X-ray diffraction analyses revealed that <b>1</b>–<b>3</b> consist of planar centrosymmetric hexanuclear clusters built from Fe^III and Ln^III ions linked by an array of bridging carboxylate, azide, and aminopolyalcoholato-based ligands into a cyclic structure with a cavity, and with distinct sets of crystal solvents (2 EtOH per formula unit in <b>1a</b>–<b>c</b>, 2 CH₂Cl₂ in <b>2</b>, and 2 EtOH and 2 CH₂Cl₂ in <b>3</b>). In <b>4</b>–<b>10</b>, the largest 3d/4f wheels currently known, nearly linear Fe₃ fragments are joined via mononuclear Ln/Y units by a set of isobutyrates and amino alcohol ligands into virtually planar rings. The magnetic properties of <b>1</b>–<b>10</b> reveal slow magnetization relaxation for {Fe₄Tb₂} (<b>1d</b>) and slow relaxation for {Fe₄Ho₂} (<b>1c</b>), {Fe₁₈Dy₆} (<b>4</b>), and {Fe₁₈Tb₆} (<b>6</b>)

Assembly of Cerium(III) 2,2′-Bipyridine-5,5′-dicarboxylate-based Metal–Organic Frameworks by Solvent Tuning

Small changes to the reaction conditions differentiate between two metal–organic frameworks (MOFs), {[Ce₂(H₂O)­(bpdc)₃(dmf)₂]·2­(dmf)}_<i>n</i> (<b>1</b>) and {[Ce₄(H₂O)₅(bpdc)₆(dmf)]·<i>x</i>(dmf)}_<i>n</i> (<b>2</b>), that were solvothermally synthesized from cerium­(III) nitrate hexahydrate and 2,2′-bipyridine-5,5′-dicarboxylic acid (H₂bpdc) in dimethylformamide (dmf). The two compounds illustrate how the flexibility of the coordination geometry of Ce^III translates into MOFs, the formation of which readily adapts to different solvent environments