10.1021/ja3010539.s002
Bo Zheng
Bo
Zheng
Xu-Dong Chen
Xu-Dong
Chen
Shao-Liang Zheng
Shao-Liang
Zheng
R. H. Holm
R. H.
Holm
Selenium as a Structural
Surrogate of Sulfur: Template-Assisted
Assembly of Five Types of Tungsten–Iron–Sulfur/Selenium
Clusters and the Structural Fate of Chalcogenide Reactants
American Chemical Society
2016
W 2Fe
EBDC
W 2Fe core
assembly
WFe 3S cubane cores
Tp
cluster
terminal iron ligation
Na 2Se yields
2016-02-21 14:53:43
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Selenium_as_a_Structural_Surrogate_of_Sulfur_Template_Assisted_Assembly_of_Five_Types_of_Tungsten_Iron_Sulfur_Selenium_Clusters_and_the_Structural_Fate_of_Chalcogenide_Reactants/2531920
Syntheses of five types of tungsten–iron–sulfur/selenium
clusters, namely, incomplete cubanes, single cubanes, edge-bridged
double cubanes (EBDCs), P<sup>N</sup>-type clusters, and double-cuboidal
clusters, have been devised using the concept of template-assisted
assembly. The template reactant is six-coordinate [(Tp*)W<sup>VI</sup>S<sub>3</sub>]<sup>1–</sup> [Tp* = tris(3,5-dimethylpyrazolyl)hydroborate(1−)],
which in the assembly systems organizes Fe<sup>2+/3+</sup> and sulfide/selenide
into cuboidal [(Tp*)WFe<sub>2</sub>S<sub>3</sub>] or cubane [(Tp*)WFe<sub>3</sub>S<sub>3</sub>Q] (Q = S, Se) units. With appropriate terminal
iron ligation, these units are capable of independent existence or
may be transformed into higher-nuclearity species. Selenide is used
as a surrogate for sulfide in cluster assembly in order to determine
by X-ray structures the position occupied by an external chalcogenide
nucleophile or an internal chalcogenide atom in the product clusters.
Specific incorporation of selenide is demonstrated by the formation
of [WFe<sub>3</sub>S<sub>3</sub>Se]<sup>2+/3+</sup> cubane cores.
Reductive dimerization of the cubane leads to the EBDC core [W<sub>2</sub>Fe<sub>6</sub>S<sub>6</sub>Se<sub>2</sub>]<sup>2+</sup> containing
μ<sub>4</sub>-Se sites. Reaction of these species with HSe<sup>–</sup> affords the P<sup>N</sup>-type cores [W<sub>2</sub>Fe<sub>6</sub>S<sub>6</sub>Se<sub>3</sub>]<sup>1+</sup>, in which
selenide occupies μ<sub>6</sub>-Se and μ<sub>2</sub>-Se
sites. The reaction of [(Tp*)WS<sub>3</sub>]<sup>1–</sup>,
FeCl<sub>2</sub>, and Na<sub>2</sub>Se yields the double-cuboidal
[W<sub>2</sub>Fe<sub>4</sub>S<sub>6</sub>Se<sub>3</sub>]<sup>2+/0</sup> core with μ<sub>2</sub>-Se and μ<sub>4</sub>-Se bridges.
It is highly probable that in analogous sulfide-only assembly systems,
external and internal sulfide reactants occupy corresponding positions
in the cluster products. The results further demonstrate the viability
of template-assisted cluster synthesis inasmuch as the reduced (Tp*)WS<sub>3</sub> unit is present in all of the clusters. Structures, zero-field
Mössbauer data, and redox potentials are presented for each
cluster type.