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Isopolymolybdates Heteropolytungstates

Isopolymolybdates Heteropolytungstates. Formation and Structure. Examples. V 10 O 28 2- Mo 7 O 24 6- Mo 8 O 26 4- Ta 6 O 19 8- Al 13 O 4 (OH) 24 (H 2 O) 12 7+ or AlO 4 Al 12 (OH) 24 (H 2 O) 12 7+ PW 12 O 40 3- P 2 W 18 O 62 6- Co 4 P 4 W 30 O 112 (H 2 O) 2 16-

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Isopolymolybdates Heteropolytungstates

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  1. IsopolymolybdatesHeteropolytungstates Formation and Structure

  2. Examples V10O282- Mo7O246- Mo8O264- Ta6O198- Al13O4(OH)24(H2O)127+ or AlO4Al12(OH)24(H2O)127+ PW12O403- P2W18O626- Co4P4W30O112(H2O)216- or Co4(H2O)2(P2W15O56)216- As12Ln16(H2O)36W148O52476-

  3. ? ? ? How do we make sense of these?

  4. Chromate - Dichromate CrO42- + 2 H+ → Cr2O72- + H2O yellow orange Think of CrO42- as being composed of 4 O2- with a central Cr6+ One O2- is neutralized by the acid. O2- + 2 H+ → H2O

  5. Chromate - Dichromate The Cr2O72- ion has each Cr at the center of a tetrahedron with the two tetrahedrons sharing a corner.

  6. Chromate ionDichromate ion

  7. Molybdates Molybdates form polyions by edge sharing rather than corner sharing. The Mo6+ ions are at the center of an octahedron.

  8. Polymolybdates Unlike chromates. MoO42- → Mo7O246- → Mo8O264- → Mo36O1128-

  9. Molybdates and Tungstates What three structures can be built from three octahedrons by edge sharing? No corner sharing. No face sharing.

  10. 1 1

  11. 2 2

  12. 3 3

  13. 3 From Opposite Side 3

  14. What’s in the Literature? Lots of errors in the older literature. Systems not at equilibrium when measured, especially tungsten systems. Bad theory. Assumed that diffusion in solution was only related to molecular weight (like gases).

  15. Isopolymolybdates Maximize 60°; minimize others

  16. Keggin Structure When structures get large, must have some corner sharing.

  17. A Heteropolytungstate: W12O408-

  18. Another View

  19. Synthesis Product depends on: stoichiometry of reactants pH temperature A variety of ions can be put into the cavity. P(V), Si(IV), Co(II), Co(III), C(IV), . . .

  20. Synthesis Can also have a heteroion replace one of the tungstens. A P(V) in the center and a Co(II) replacing a W. A Co(II) in the center and a Co(II) replacing a W.

  21. Synthesis Co2+ + WO42- → CoW11Co(H2O)O398- precipitate potassium salt CoW11Co(H2O)O398- + H+ → CoW12O406- (aq) this contains Co2+ in the center Oxidize to Co3+ → CoW12O405- precipitate as potassium salt Result: tetrahedral Co(III) in the center

  22. Lacunary Structures Can have structures with a piece of the regular structure missing. Remove a W3 unit from the Keggin structure and have a W9 structure remaining. Put two of those W9 structures together and get the Dawson structure.

  23. Dawson Structure P2W18O626-

  24. The Compound with Four Cobalts Co4(H2O)2(P2W15O56)216-

  25. M(H2O)P5W30O11014-The Lemon Green: metal ion Blue: water Red: phosphorus

  26. As12Ln16(H2O)36W148O52476-

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