10.1021/ic049517s.s001
Travis M. Anderson
Travis M.
Anderson
Wade A. Neiwert
Wade A.
Neiwert
Kenneth I. Hardcastle
Kenneth I.
Hardcastle
Craig L. Hill
Craig L.
Hill
Multi-Iron Silicotungstates: Synthesis, Characterization, and Stability
Studies of Polyoxometalate Dimers
American Chemical Society
2004
WO
μ 2 oxo ligand
3 O 34
OH
3 equiv
trisubstituted Keggin unit
UV
pH
0.5 M sodium acetate solution
2 FeW 9
Differential scanning calorimetry data show
SiW
2004-11-15 00:00:00
Dataset
https://acs.figshare.com/articles/dataset/Multi_Iron_Silicotungstates_Synthesis_Characterization_and_Stability_Studies_of_Polyoxometalate_Dimers/3315904
The reaction of Fe(III) with Na<sup>+</sup> and K<sup>+</sup> salts of the trivacant [α-SiW<sub>9</sub>O<sub>34</sub>]<sup>10-</sup> ligand have been investigated at pH
6 and pH 1. A new dimer, [(α-SiFe<sub>3</sub>W<sub>9</sub>(OH)<sub>3</sub>O<sub>34</sub>)<sub>2</sub>(OH)<sub>3</sub>]<sup>11-</sup> (<b>1</b>), is synthesized by reacting Na<sub>7</sub>H<sub>3</sub>[α-SiW<sub>9</sub>O<sub>34</sub>] or
K<sub>10</sub>[α-SiW<sub>9</sub>O<sub>34</sub>] with exactly 3 equiv of Fe(III) in a 0.5 M sodium acetate solution (pH 6). The structure of <b>1</b>,
determined by single-crystal X-ray diffraction (<i>a</i> = 22.454(2) Å, <i>b</i> = 12.387(2) Å, <i>c</i> = 37.421(2), β = 100.107(8)°,
monoclinic, <i>C</i>2/<i>c</i>, <i>Z</i> = 4, R<sub>1</sub> = 5.11% based on 12739 independent reflections), consists of two [α-SiFe<sub>3</sub>W<sub>9</sub>(OH)<sub>3</sub>O<sub>34</sub>]<sup>4-</sup> units linked by three Fe−μ-OH−Fe bonds. Reaction of K<sub>10</sub>[α-SiW<sub>9</sub>O<sub>34</sub>] with 3 equiv of Fe(III) in water
(pH 1) yields [(α-Si(FeOH<sub>2</sub>)<sub>2</sub>FeW<sub>9</sub>(OH)<sub>3</sub>O<sub>34</sub>)<sub>2</sub>]<sup>8-</sup> (<b>2</b>). The structure of <b>2</b> was also determined by single-crystal X-ray
diffraction (<i>a</i> = 36.903(2) Å, <i>b</i> = 13.9868(9) Å, <i>c</i> = 21.7839(13) Å, β = 122.709(1)°, monoclinic, <i>C</i>2/<i>c</i>, <i>Z</i> = 4,
R<sub>1</sub> = 4.57% based on 11787 independent reflections). It consists of two [α-Si(FeOH<sub>2</sub>)<sub>2</sub>FeW<sub>9</sub>(OH)<sub>3</sub>O<sub>34</sub>]<sup>4-</sup> Keggin
units linked by a single edge. The terminal ligand on Fe1 in each trisubstituted Keggin unit becomes a μ<sub>2</sub> oxo
ligand bridging to a [WO<sub>6</sub>]<sup>2-</sup> moiety. The UV−vis spectra of both complexes show the characteristic oxygen-to-metal-charge-transfer bands of polyoxometalates as well as an Fe(III)-centered band at 436 nm (ε = 146 M<sup>-1</sup>
cm<sup>-1</sup>) and 456 nm (ε = 104 M<sup>-1</sup> cm<sup>-1</sup>) for complexes <b>1</b> and <b>2</b>, respectively. Differential scanning calorimetry data
show that complex <b>1</b> decomposes between 575 and 600 °C whereas no decomposition is observed for complex
<b>2</b> up to temperatures of 600 °C.