Facile Reduction of Tungsten Halides with Nonconventional, Mild Reductants. 2. Four Convenient, High-Yield Solid-State Syntheses of the Hexatungsten Dodecachloride Cluster W6Cl12 and Cluster Acid (H3O)2[W6(μ3-Cl) 8Cl6](OH2)x, Including New Cation-Assisted Ternary Routes

Abstract

Tungsten hexachloride was reduced by Hg or Bi at moderately low temperatures (∼350 °C) to afford good yields (Hg, 73%; Bi, 85%) of W6Cl12 after conversion of the reduction product to the chloro acid (H3O)2[W6(μ3-Cl) 8-Cl6](OH2)x, recrystallization, and thermolysis in vacuo. Antimony was a less effective reductant because of the lower yield of chloro acid (31%) and the substantial quantities of insoluble byproducts found after HCl workup. The yield of (H3O)2[W6(μ3-Cl) 8Cl6](OH2)x from WCl6 reduction by Sb improved dramatically to 79% with added KCl, while LiCl reduced the yield to only traces. In Bi reduction of WCl6, the yield of (H3O)2[W6(μ3-Cl) 8Cl6]-(OH2)X decreased from 86 to 49% upon addition of NaCl, whereas added KCl had no effect on the yield. The Hg-, Bi-, Sb/KCl-, and Bi/KCl-based routes offer substantial experimental advantages over published methods for preparation of (H3O)2[W6(μ3-Cl) 8Cl6](OH2)x and W6Cl12.