Host-Guest Chemistry in Discrete Polyoxo-12-Palladate(II) Cubes [MO8Pd12L8]n- (M = ScIII, CoII, CuII, L = AsO43 -; M = CdII, HgII, L = PhAsO32-): Structure, Magnetism, and Catalytic Hydrogenation.

A family of five host-guest assemblies comprising different metal ions inside a cuboid 12-palladium-oxo cage, [MO8Pd12L8]n- (MPd12L8, M = ScIII, CoII, CuII, L = AsO43-; M = CdII, HgII, L = PhAsO32-), was synthesized and structurally characterized in the solid state by single-crystal X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis, and their solution and gas-phase stability were validated by multinuclear NMR spectroscopy and electrospray-ionization mass spectrometry (ESI-MS). The polyoxopalladates (POPs) ScPd12As8, CoPd12As8, and CuPd12As8 represent the first three examples of the MPd12As8 archetype. The unique cubic ligand field of {MO8} allows for collecting the speciation profiles of the POPs in solution using 45Sc and 113Cd NMR techniques. Detailed magnetic and electron paramagnetic resonance (EPR) studies were performed on CuPd12As8. Catalytic studies on MPd12As8 (M = CuII and CoII) supported on SBA-15 unveiled a guest metal-dependent structure-function relationship, with CuPd12As8 being the more efficient precatalyst for the hydroconversion of o-xylene in a fixed-bed reactor.

Discrete Silver(I)-Palladium(II)-Oxo Nanoclusters, {Ag4 Pd13 } and {Ag5 Pd15 }, and the Role of Metal-Metal Bonding Induced by Cation Confinement.

We introduce the class of discrete silver(I)-palladium(II)-oxo nanoclusters with the preparation of {Ag4 Pd13 } and {Ag5 Pd15 }. Both polyanions represent the first examples of noble metal-capped polyoxo-noble-metalates in a fully inorganic assembly, featuring an unprecedented host-guest mode containing hetero- and homometallic Ag-Pd and Ag-Ag bonding interactions. Comprehensive theoretical calculations suggest that the Ag-Pd metallic bonds originate partially from surface confinement of AgI guest ions onto the anionic polyoxopalladate host that is induced by strong electrostatic forces. This work opens the field of fully inorganic silver-palladium-oxo nanoclusters, which can be considered as discrete mixed noble metal precursors for the formation of monodisperse core-shell nanoparticles, with high relevance for catalysis.

Tetradecanuclear Iron(III)-Oxo Nanoclusters Stabilized by Trilacunary Heteropolyanions.

The tetrameric, multi-Fe(III)-containing polyoxotungstates [Fe14O6(OH)13(P2W15O56)4](31-) (1) and [Na2Fe14(OH)12(PO4)4(A-α-XW9O34)4](20-) (X = Si(IV) (2), Ge(IV) (3)) have been successfully synthesized under conventional reaction conditions in aqueous, slightly acidic (1), or basic (2 and 3) media. Polyanions 1-3 were characterized in the solid state by single-crystal X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and magnetic studies, and in solution by electrochemistry.

Alkaline earth guests in polyoxopalladate chemistry: from nanocube to nanostar via an open-shell structure.

The three novel, discrete palladium(II)-oxo clusters [CaPd12O8(PhAsO3)8](6-) (CaPd12), [SrPd12O6(OH)3(PhAsO3)6(OAc)3](4-) (SrPd12), and [BaPd15O10(PhAsO3)10](8-) (BaPd15) encapsulating alkaline earth metal ions were prepared and fully characterized by a multitude of solution and solid-state physicochemical techniques. We have discovered a structure-directing template effect induced by the respective size of the alkaline earth guest ion, which determines the detailed condensation arrangement of the peripheral Pd(II)-oxo shell. The unprecedented SrPd12 with an open-shell type structure is of particular importance and reflects a successful strategy for deliberate design of new structural classes of polyoxo-noble-metalates. Furthermore, the unusual acetate-water ligand exchange phenomenon renders SrPd12 as a promising candidate for noble-metal-based catalysis.

Synthesis, magnetism, and electrochemistry of the Ni14- and Ni5-containing heteropolytungstates [Ni14(OH)6(H2O)10(HPO4)4(P2W15O56)4]34- and [Ni5(OH)4(H2O)4(ß-GeW9O34)(ß-GeW8O30(OH))]13-.

The two Ni(2+)-containing heteropolytungstates [Ni14(OH)6(H2O)10(HPO4)4(P2W15O56)4](34-) (Ni14) and [Ni5(OH)4(H2O)4(ß-GeW9O34)(ß-GeW8O30(OH))](13-) (Ni5) have been successfully synthesized in aqueous, basic media under conventional reaction conditions, and they were characterized by single-crystal X-ray diffraction, IR spectroscopy, thermogravimetric and elemental analyses, electrochemistry, and magnetic studies. The cyclic voltammetry (CV) patterns of Ni14 and Ni5 showed chemically reversible multielectronic waves for slow scan time scales. For Ni14, an important acidity inversion effect between its reduced forms was observed. Magnetic studies revealed dominant ferromagnetic interactions among the nickel(II) ions in both polyanions.

Heptanickel(ii) double-cubane core in wells-dawson heteropolytungstate, [Ni7(OH)6(H2O)6(P2W15O56)2](16-).

The hepta-Ni(2+)-containing 30-tungsto-4-phosphate(v) [Ni7(OH)6(H2O)6(P2W15O56)2](16-) (1) has been synthesized in aqueous, slightly basic medium under conventional reaction conditions, and charactarized via different physical methods. Single-crystal XRD showed that 1 consists of a corner-fused double-cubane {Ni7(OH)6(H2O)6}(8+) fragment sandwiched by two trilacunary [P2W15O56](12-) units. Polyanion 1 is solution-stable as shown by (31)P NMR. Ferromagnetic coupling interaction between the 7 paramagnetic centers of the double-cubane core in 1 with a S = 7 ground state was demonstrated. Electrochemical studies were also performed on 1.

The selenite-capped polyoxo-4-aurate(III), [Au(III)4O4(Se(IV)O3)4]4-.

The discrete heteropolyaurate [Au(III)(4)O(4)(Se(IV)O(3))(4)](4-) (Au(4)Se(4)) represents only the second member of this class ever reported, and was synthesized via one-pot room temperature condensation in aqueous medium. was structurally characterized in the solid state and in solution by single-crystal XRD, TGA, FT-IR, (77)Se NMR, mass spectrometry and electrochemistry.