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The two dimeric, Hf-containing tungstosilicates [Hf4(OH)6(CH3COO)2(α-SiW10O37)2]12−(1) and [Hf4(OH)6(CH3COO)2(β-SiW10O37)2]12−(2) have been synthesized by reacting HfCl4with [γ-SiW10O36]8−in potassium acetate solutions at pH = 3.6 and 4.8, respectively. Polyanions 1and 2comprise a tetrahafnium(iv) assembly {Hf4(OH)6(CH3COO)2} sandwiched between two dilacunary [α-SiW10O36]8−(in 1) or {β-SiW10} (in 2) Keggin type decatungstosilicates. This implies that the starting precursor {γ-SiW10} isomerizes in situto [β-SiW10O37]10−and then to [α-SiW10O37]10−by controlled variation of pH and temperature. The hydrated potassium salts of 1and 2were investigated in the solid state by single-crystal XRD, FT-IR, thermogravimetric and elemental analyses, and in solution by UV-Vis and 183W NMR spectroscopy, and electrochemistry. [ABSTRACT FROM AUTHOR]

The carbonyl–ruthenium substituted undecatungstosilicate [α-SiW11O39RuII(CO)]6−(1) was isolated as a caesium salt and successfully characterized by using 183W and 13C NMR, elemental analysis, IR, UV-vis and cyclic voltammetry (CV). Polyanion 1represents the first example of a metal–carbonyl moiety being fully incorporated into the polyoxometalate (POM). As a result, the Ru(CO) moiety became redox active and was reversibly oxidized to the one-electron ruthenium(iii) derivative, [α-SiW11O39RuIII(CO)]5−. This RuIII(CO) moiety was unexpectedly stable in aqueous solution compared to the organo–ruthenium carbonyl derivatives and could be detected by using UV-vis and in situIR coupled with electrolysis. The oxidized ruthenium(iii) derivative slowly released CO in aqueous solution, resulting in the aqua species [α-SiW11O39RuIII(H2O)]5−and then the dimeric POM species by condensation. Furthermore, 1could be converted to the corresponding aqua polyanion by photo-irradiation. [ABSTRACT FROM AUTHOR]

We report the dimerization of a mono-ruthenium(iii) substituted α-Keggin-type tungstosilicate [α-SiW11O39RuIII(H2O)]5− to a µ-oxo-bridged dimer [{α-SiW11O39Rum}2O]n− (m = iii, n = 12; m = iv/iii, n = 11; m = iv, n = 10). Single crystal X-ray structure analysis of Rb10[{α-SiW11O39RuIV}2O]·9.5H2O (triclinic, P1̄, with a = 12.7650(6) Å, b = 18.9399(10) Å, c = 20.2290(10) Å, α = 72.876(3)°, β = 88.447(3)°, γ = 80.926(3)°, V = 4614.5(4) Å3, Z = 2) reveals that two mono-ruthenium substituted tungstosilicate α-Keggin units are connected through µ-oxo-bridging Ru–O–Ru bonds. Solution 183W-NMR of [{SiW11O39RuIV}2O]10− resulted in six peaks (−63, −92, −110, −128, −132, and −143 ppm, intensities 2 : 2 : 1 : 2 : 2 : 2) confirming that the µ-oxo bridged dimer structure is maintained in aqueous solution. The dimerization mechanism is presumably initiated by deprotonation of the aqua-ruthenium complex [α-SiW11O39RuIII(H2O)]5− leading to a hydroxy-ruthenium complex [α-SiW11O39RuIII(OH)]6−. Dimerization of two hydroxy-ruthenium complexes produces the µ-oxo bridged dimer [{α-SiW11O39RuIII}2O]12− and a water molecule. The Ru(iii) containing dimer is oxidized by molecular oxygen to produce a mixed valence species [{α-SiW11O39RuIV-III}2O]11−, and further oxidation results in the Ru(iv) containing [{α-SiW11O39RuIV}2O]10−. [ABSTRACT FROM AUTHOR]

Reaction of [Ru(p-cymene)Cl2]2 with [H7P8W48O184]33− (P8W48) in aqueous acidic medium results in the organometallic derivative [{K(H2O)}3{Ru(p-cymene)(H2O)}4P8W49O186(H2O)2]27− (1); in addition to the four {Ru(p-cymene)(H2O)} units, an unusual WO6 group with four equatorial, terminal ligands is also grafted to the crown-shaped P8W48 precursor. [ABSTRACT FROM AUTHOR]

A novel heteropolyoxopalladate structural type has been discovered: the polyoxo-15-palladate(II) [Pd0.4Na0.6⊂Pd15P10O50H6.6]12−(Pd15) has been prepared in a one-pot self-assembly reaction and characterized by single-crystal XRD, elemental analysis, IR, TGA, 31P NMR and electrochemistry; preliminary catalytic studies showed that Pd15is active as a catalyst in alcohol oxidation by dioxygen. [ABSTRACT FROM AUTHOR]