No abstract

The previously unknown heteropolyoxometalates [gamma-SiO(4)W(10)O(32)(OH)Cr(2)(OOCR)(2)(OH(2))(2)](5-) (R = H, CH(3)) have been prepared by the reaction of [gamma-SiO(4)W(10)O(32)](8-) with [Cr(OH(2))(6)](3+) in formate or acetate buffer solution. Isolation of these new Cr(III)-substituted polyoxometalates was accomplished both as Cs(+) salts and as the Bu(4)N(+) salt for the acetate-containing anion. The compounds were characterized by elemental analysis, UV/vis, IR, and ESR spectroscopy, and cyclic voltammetry. The single-crystal X-ray structural analysis of (Bu(4)N)(3)H(2)[gamma-SiO(4)W(10)O(32)(OH)Cr(2)(OOCCH(3))(2)(OH(2))(2)].3H(2)O [P2(1)2(1)2(1); a = 17.608(12), b = 20.992(13), c = 24.464(11) Å; Z = 4; R = 0.057 for 6549 observed independent reflections] reveals that the two corner-linked CrO(6) octahedra are additionally bridged by two acetate groups, demonstrating the relationship to the well-studied oxo-centered trinuclear carboxylato complexes of Cr(III).

Abstract Dodecatungstosilicates free of crystal water were prepared for the first time by using tetraalkylammonium as cation. The crystal structure of the tetramethylammonium a-dodeeatungstosilicate [N(CH3)4]4SiW12O40 (1) and tetrabutylammonium) β-dodecatungstosilicate, [N(C4H9)4]4SiWi2040 (2) were solved by X-ray diffraction. (1) crystallizes tetragonal in the space group 14̅ with lattice parameters a = 14.642 Å; c= 12.706 Å; (2) orthorhombic, space group P212121 with a = 29.277 Å, b = 22.181 Å and c = 15.381 Å. The differences between the two isomeric heteropolyanions are discussed, especially the distances and angles between the tungsten atoms. Comparison of characteristic differences in the vibrational spectra permits the identification of the isomeric anions.

It was clear that activation was taking place, but the initial products, which are more reactive than the starting alkane and still volatile, were reacting further. To avoid this, we devised a simple reactor (Fig. 1) in which the gas mixture is cycled by a peristaltic pump through a photolysis chamber and then into a cold trap (-20 "C) to remove the initial photoproducts. We find that this leads to efficient amination 1494 ' <: .

AbstractThe title compound crystallizes monoclinicly in the space group P21/c with lattice parameters a = 13.522 Å, b = 22.379 Å, c = 15.071 Å und β = 95.95°. In the polyanion two α-PW9O34 moieties are bridged by two octahedral WO6 units. A potassium ion in the central cavity is surrounded by eight oxygen atoms of the polyanion in hexagonal bipyramidal coordination. - The vibration spectrum of the solid and its aqueous solution are discussed.