Synthesis, Structure, and Reactivity of [Zr₆Cl₁₈H₅]^2-, the First Paramagnetic Species of Its Class

Reaction of [Zr6Cl18H5]3- (1) with 1 equiv of TiCl4 yields a new cluster anion, [Zr6Cl18H5]2- (2), which can be converted back into [Zr6Cl18H5]3- (1) upon addition of 1 equiv of Na/Hg. Cluster 2 is paramagnetic and unstable in the presence of donor molecules. It undergoes a disproportionation reaction to form 1, some Zr(IV) compounds, and H2. It also reacts with TiCl4 to form [Zr2Cl9]- (4) and a tetranuclear mixed-metal species, [Zr2Ti2Cl16]2- (3). The oxidation reaction of 1 with TiCl4 is unique. Oxidation of 1 with H+ in CH2Cl2 solution results in the formation of [ZrCl6]2- (5) and H2, while in py solution the oxidation product is [ZrCl5(py)]- (6). There is no reaction between 1 and TiI4, ZrCl4, [TiCl6]2-, [ZrCl6]2-, or CrCl3. Compounds [Ph4P]2[Zr6Cl18H5] (2a), [Ph4P]2[Zr2Ti2Cl16] (3a), [Ph4P]2[Zr2Cl9] (4a), [Ph4P]2[ZrCl6]·4MeCN (5a·4MeCN), and [Ph4P][ZrCl5(py)] (6a) were characterized by X-ray crystallography. Compound 2a crystallized in the trigonal space group R3̄ with cell dimensions (20 °C) of a = 28.546(3) Å, b = 28.546(3) Å, c = 27.679(2) Å, V = 19533(3) Å3, and Z = 12. Compound 3a crystallized in the triclinic space group P1̄ with cell dimensions (−60 °C) of a = 11.375(3) Å, b = 13.357(3) Å, c = 11.336(3) Å, α = 106.07(1)°, β = 114.77(1)°, γ = 88.50(1)°, V = 1494.8(7) Å3, and Z = 1. Compound 4a crystallized in the triclinic space group P1̄ with cell dimensions (−60 °C) of a = 12.380(5) Å, b = 12.883(5) Å, c = 11.000(4) Å, α = 110.39(7)°, β = 98.29(7)°, γ = 73.12(4)°, V = 1572(1) Å3, and Z = 2. Compound 5a·4MeCN crystallized in the monoclinic space group P21/c with cell dimensions (−60 °C) of a = 9.595(1) Å, b = 19.566(3) Å, c = 15.049(1) Å, β = 98.50(1)°, V = 2794.2(6) Å3, and Z = 2. Compound 6a crystallized in the monoclinic space group P21/c with cell dimensions (20 °C) of a = 10.3390(7) Å, b = 16.491(2) Å, c = 17.654(2) Å, β = 91.542(6)°, V = 3026.4(5) Å3, and Z = 4

Synthesis and Structural Characterization of Compounds Containing the [Zr₆Cl₁₈H₅]^3- Cluster Anion. Determination of the Number of Cluster Hydrogen Atoms

Reduction of ZrCl4 with HSnBu3 followed by addition of [R4A]Cl resulted in the formation of [R4A]3[Zr6Cl18H5] (2a, R = Ph, A = P; 2b, R = n-Pr, A = N; 2c, R = Et, A = N). Six zirconium atoms are arranged as an octahedron with one Cl atom terminally coordinated to each Zr atom and the other 12 Cl atoms edge-bridging the octahedron. When [Ph4P]I was used, the compound [Ph4P]3[Zr6Cl18-xIxH5] (x = 0.81) (3) was isolated. In compound 3, I atoms occupy only the terminal positions. The number of cluster hydrogen atoms in compounds 2a−c and 3 was established by 1H NMR. The X-ray results are consistent with the five cluster hydrogen atoms being distributed at or slightly outside the centers of all eight triangular faces of the octahedron. Compounds 2a−c and 3 were characterized by X-ray single-crystal diffraction. Compound 2a·3CH2Cl2 crystallized in the triclinic space group P1̄ with cell dimensions (20 °C) of a = 15.993(3) Å, b = 22.237(3) Å, c = 14.670(4) Å, α = 95.31(1)°, β = 112.07(2)°, γ = 82.06(2)°, V = 4784(2) Å3, and Z = 2. Compound 2a crystallized in the tetragonal space group I41/a with cell dimensions (20 °C) of a = 33.196(2) Å, b = 33.196(2) Å, c = 15.236(2) Å, V = 16790(3) Å3, and Z = 8. Compound 2a·4C6H5CH3 crystallized in the triclinic space group P1̄ with cell dimensions (−60 °C) of a = 14.501(5) Å, b = 26.630(9) Å, c = 14.049(5) Å, α = 90.39(3)°, β = 94.19(3)°, γ = 82.59(1)°, V = 5365(3) Å3, and Z = 2. Compound 2b crystallized in the cubic space group Im3̄m with cell dimensions (−60 °C) of a = 15.039(3) Å, b = 15.039(3) Å, c = 15.039(3) Å, V = 3438(1) Å3, and Z = 2. Compound 2c·2.43MeCN crystallized in the orthorhombic space group Pnma with cell dimensions (−100 °C) of a = 21.156(1) Å, b = 24.584(3) Å, c = 11.713(2) Å, V = 6092(1) Å3, and Z = 4. Compound 3·3CH2Cl2·C6H5CH3 crystallized in the monoclinic space group P21/c with cell dimensions (20 °C) of a = 19.786(5) Å, b = 19.071(4) Å, c = 27.397(5) Å, β = 90.22(3)°, V = 10337(4) Å3, and Z = 4

Zirconium Clusters from the Reaction of ZrCl₄ with HSnBu₃ Followed by Addition of Phosphines: Zr₆Cl₁₄H₄(PR₃)₄ Compounds

The reduction of ZrCl4 with HSnBu3 followed by addition of phosphines yields pentanuclear cluster compounds Zr5Cl12(PR3)5H4 (2) and three types of hexanuclear cluster compounds, Zr6Cl14(PR3)4H4 (3), as well as [Zr6Cl18H5]3- (4) and a small amount of [Zr6Cl18H4]4- (5). Separation of these compounds has been achieved by using different solvents in which they have different solubilities and stabilities. The presence of hydrogen atoms and their numbers have been established by 1H NMR spectroscopy. The compounds Zr6Cl14(PR3)4H4 (3a, R = Me; 3b, R = Et; 3c, R = n-Pr) and [HP(t-Bu)2Ph]3[Zr6Cl18H5] (4d) have been characterized by X-ray crystallography. In compounds 3a and 3b, four hydrogen atoms distributed on the eight triangular faces of the Zr6 octahedron were located. Compound 3a·2CH2Cl2 crystallized in the monoclinic space group P21/n with cell dimensions (−75 °C) of a = 11.149(2) Å, b = 11.049(4) Å, c = 20.666(7) Å, β = 103.42(2)°, V = 2476(1) Å3, and Z = 2. Compound 3b·2CH2Cl2 crystallized in orthorhombic space group Pbca with cell dimensions (−60 °C) of a = 12.127(3) Å, b = 21.793(5) Å, c = 23.022(4) Å, V = 6084(2) Å3, and Z = 4. Compound 3c·2.31C6H6 crystallized in triclinic space group P1̄ with cell dimensions (−60 °C) of a = 12.585(1) Å, b = 13.679(2) Å, c = 23.319(4) Å, α = 97.08(2)°, β = 94.77(2)°, γ = 93.30(2)°, V = 3960.6(9) Å3, and Z = 2. Compound 4d·2CH2Cl2·2C6H6 crystallized in monoclinic space group C2/c with cell dimensions (−60 °C) of a = 29.432(4) Å, b = 13.503(1) Å, c = 23.892(3) Å, β = 110.96(1)°, V = 8867(2) Å3, and Z = 4. In compounds 3a−c, six zirconium atoms are arranged in a slightly elongated octahedron with four phosphine ligands at the equatorial positions. The distance of Zreq−Zrax (3.359(8) Å) is slightly longer that of Zreq−Zreq (3.308(6) Å), but both of them are shorter than that found in compound 4d (3.416(2) Å)

Zirconium Clusters from the Reaction of ZrCl₄ with HSnBu₃ Followed by Addition of Phosphines: Zr₆Cl₁₄H₄(PR₃)₄ Compounds

The reduction of ZrCl4 with HSnBu3 followed by addition of phosphines yields pentanuclear cluster compounds Zr5Cl12(PR3)5H4 (2) and three types of hexanuclear cluster compounds, Zr6Cl14(PR3)4H4 (3), as well as [Zr6Cl18H5]3- (4) and a small amount of [Zr6Cl18H4]4- (5). Separation of these compounds has been achieved by using different solvents in which they have different solubilities and stabilities. The presence of hydrogen atoms and their numbers have been established by 1H NMR spectroscopy. The compounds Zr6Cl14(PR3)4H4 (3a, R = Me; 3b, R = Et; 3c, R = n-Pr) and [HP(t-Bu)2Ph]3[Zr6Cl18H5] (4d) have been characterized by X-ray crystallography. In compounds 3a and 3b, four hydrogen atoms distributed on the eight triangular faces of the Zr6 octahedron were located. Compound 3a·2CH2Cl2 crystallized in the monoclinic space group P21/n with cell dimensions (−75 °C) of a = 11.149(2) Å, b = 11.049(4) Å, c = 20.666(7) Å, β = 103.42(2)°, V = 2476(1) Å3, and Z = 2. Compound 3b·2CH2Cl2 crystallized in orthorhombic space group Pbca with cell dimensions (−60 °C) of a = 12.127(3) Å, b = 21.793(5) Å, c = 23.022(4) Å, V = 6084(2) Å3, and Z = 4. Compound 3c·2.31C6H6 crystallized in triclinic space group P1̄ with cell dimensions (−60 °C) of a = 12.585(1) Å, b = 13.679(2) Å, c = 23.319(4) Å, α = 97.08(2)°, β = 94.77(2)°, γ = 93.30(2)°, V = 3960.6(9) Å3, and Z = 2. Compound 4d·2CH2Cl2·2C6H6 crystallized in monoclinic space group C2/c with cell dimensions (−60 °C) of a = 29.432(4) Å, b = 13.503(1) Å, c = 23.892(3) Å, β = 110.96(1)°, V = 8867(2) Å3, and Z = 4. In compounds 3a−c, six zirconium atoms are arranged in a slightly elongated octahedron with four phosphine ligands at the equatorial positions. The distance of Zreq−Zrax (3.359(8) Å) is slightly longer that of Zreq−Zreq (3.308(6) Å), but both of them are shorter than that found in compound 4d (3.416(2) Å)

Co²⁺-Linked [NaP₅W₃₀O₁₁₀]¹⁴⁻: A Redox-Active Metal Oxide Framework with High Electron Density

A new metal oxide framework based on the redox-active Preyssler anion linked with Co­(H2O)42+ bridging units is presented. The framework can be photochemically reduced, allowing the storage of multiple electrons under mild conditions. Titrations with molecular redox species show that this reduction is reversible and can accommodate up to 10 electrons per Preyssler cluster (corresponding to an electron density on the order of 1021 cm–3) without changing the crystal structure. This addition of delocalized electrons is accompanied by a 1000-fold increase in the conductivity. These results demonstrate that the ability to add delocalized electrons to polyoxometalate clusters can be incorporated into self-assembled extended solids, enabling the development and tuning of metal oxide materials with emergent or complementary properties

Host–Guest Chemistry Triggered Differential HeLa Cell Behavior Based on Pillar[5]arene-Modified Graphene Oxide Surfaces

The regulation of surface wettability and cell adhesion behavior in a mild and unperturbed state at the interface remains a challenging task. To address this task, we adopt a strategy, based on bridging the host–guest recognition capacities of pillar[5]­arene and good attachment for cell adhesion abilities of graphene oxide, to construct a smart pillar[5]­arene triazole-linked naphthalene-modified graphene oxide interface. The hybrid surface exhibited a good stimuli-responsive selectivity toward arginine, as demonstrated by the wettability and cell adhesion behavior. Further studies at molecular levels indicated that the recognition mechanism of arginine was probably due to the formation of a host–guest complex driven by π–π stacking interactions between the cavity of pillar[5]­arenes and arginine, which eventually resulted in the change in surface wettability and cellular adhesion behavior. It not only signifies a host–guest interaction strategy for the design of smart devices via the host–guest effect but also inspires the design of high-performance biointerface for affinity-adherent cells without exposing cells to harsh physical and chemical conditions

Co²⁺-Linked [NaP₅W₃₀O₁₁₀]¹⁴⁻: A Redox-Active Metal Oxide Framework with High Electron Density

A new metal oxide framework based on the redox-active Preyssler anion linked with Co­(H2O)42+ bridging units is presented. The framework can be photochemically reduced, allowing the storage of multiple electrons under mild conditions. Titrations with molecular redox species show that this reduction is reversible and can accommodate up to 10 electrons per Preyssler cluster (corresponding to an electron density on the order of 1021 cm–3) without changing the crystal structure. This addition of delocalized electrons is accompanied by a 1000-fold increase in the conductivity. These results demonstrate that the ability to add delocalized electrons to polyoxometalate clusters can be incorporated into self-assembled extended solids, enabling the development and tuning of metal oxide materials with emergent or complementary properties

Characterization and Reactions of [PPh₄]₃[Zr₆Cl₁₈H₅] and Its Deprotonation Products

The octahedral hexazirconium cluster compound [PPh4]3[Zr6Cl18H5] has been structurally characterized by both neutron and X-ray single-crystal diffraction studies. The compound [PPh4]3[Zr6Cl18H5]·3CH2Cl2 crystallizes in the triclinic space group P1̄ with unit cell parameters of a = 15.993(3), b = 22.237(3), and c = 14.670(4) Å, α = 95.31(1), β = 112.07(2), and γ = 82.06(2)°, V = 4784(2) Å3, and Z = 2 at ambient temperature and a = 15.780(6), b = 21.96(3), and c = 14.521(7) Å, α = 94.96(8), β = 111.59(4), and γ = 81.72(5)°, V = 4627(11) Å3, and Z = 2 at T = 15 K. The hydrogen atoms in the cluster anion, [Zr6Cl18H5]3-, were found to be distributed at the centers of the eight triangular faces of the Zr6 octahedron from neutron diffraction data. The occupancy parameters of the sites range from 0.32 to 0.92 with a total of 5.3(1) hydrogen atoms per cluster, close to the value from 1H NMR measurement (5.0). The average Zr−H distance is 1.96(4) Å. A variable temperature 1H NMR study indicated that the cluster hydrogen atoms undergo rapid movement at room temperature. One of the five hydrogen atoms in the cluster [Zr6Cl18H5]3- was readily removed as a proton with primary linear amines with formation of the corresponding ammonium cations, while the cluster anion, [Zr6Cl18H5]3-, was thus converted into a new cluster anion, [Zr6Cl18H4]4-. The feasibility of such a deprotonation reactions is controlled by the size of both the Lewis base and the cavity available on the Zr3 triangular faces of the Zr6 clusters, and also by the basicity of the deprotonating reagents. Two products, [PPh4]4[Zr6Cl18H4]·4CH2Cl2 and [H3NEt]4[Zr6Cl18H4]·4MeCN from the deprotonation reactions were characterized by X-ray crystallography

Co²⁺-Linked [NaP₅W₃₀O₁₁₀]¹⁴⁻: A Redox-Active Metal Oxide Framework with High Electron Density

A new metal oxide framework based on the redox-active Preyssler anion linked with Co­(H2O)42+ bridging units is presented. The framework can be photochemically reduced, allowing the storage of multiple electrons under mild conditions. Titrations with molecular redox species show that this reduction is reversible and can accommodate up to 10 electrons per Preyssler cluster (corresponding to an electron density on the order of 1021 cm–3) without changing the crystal structure. This addition of delocalized electrons is accompanied by a 1000-fold increase in the conductivity. These results demonstrate that the ability to add delocalized electrons to polyoxometalate clusters can be incorporated into self-assembled extended solids, enabling the development and tuning of metal oxide materials with emergent or complementary properties

Rationalizing the Triboelectric Series of Polymers

Rationalizing the Triboelectric Series of Polymer