Preparation
An aqueous solution of a Cr(III) compound is first reduced to the chromous state using zinc. The resulting blue solution is treated with sodium acetate, which results in the rapid precipitation of chromous acetate as a bright red powder.
- 2 Cr3+ + Zn → 2 Cr2+ + Zn2+
- 2 Cr2+ + 4 OAc- + 2 H2O → Cr2(OAc)4(H2O)2
The synthesis of Cr2(OAc)4(H2O)2 has been traditionally used to test the synthetic skills and patience of inorganic laboratory students in universities because the accidental introduction of a small amount of air into the apparatus is readily indicated by the discoloration of the otherwise bright red product. The anydrous form of chromium(II) acetate, and also related chromium(II) carboxylates, can be prepared from chromocene:
- 4 RCO2H + 2 Cr(C5H5)2 → Cr2(O2CR)4 + 4 C5H6
This method provides anhydrous derivatives in a straightforward manner.
Because it is so easily prepared, Cr2(OAc)4(H2O)2 is often used as a starting material for other, chromium(II) compounds. Also many analogues have been prepared using other carboxylic acids in place of acetate and using different bases in place of the water.
Read more about this topic: Chromium(II) Acetate
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