Vanadium Chemistry (4): (NH4)2[VO(C2O4)2(H2O)].H2O

Well, as you know, due to some incidents, during the past months my technology has grown very much, so we can try again.

In this compound, the O and H2O are cis, unlike the DMAP salt.

ref ref2

The data in the reference(the Manual also copied it) is completely a mess, but I can guess a little.

(NH4)2C2O4 + 2NH4VO3 + 4H2C2O4 = 2(NH4)2[VO(C2O4)2(H2O)].H2O + 2CO2

Attempt 1

4.68g(0.04mol) NH4VO3, 2.48g(0.02mol) (NH4)2C2O4 and 10g(0.11mol) H2C2O4 was dissolved in minimal(~30mL) water and boiled until evolution of gas ceased. Solution became blue as demonstrated long long ago. Excess of H2C2O4 can maintain acidity and ensure full reduction, and it can be washed away with EtOH.

After cooling to RT ~200mL EtOH was added and shaken. Solution immediately became opaque and black oil separated.

The upper layer was poured away and the oil was shaken with EtOH to solidify(a chopstick or something can help you a lot).

Then recrystallized with H2O/EtOH multiple times. However we found that while the upper layer was always opaque, the oil always appear and became smaller and smaller, that is to say, we are in fact purifying impurity, not product, and if we purify product as this we will simply lose everything. Damn it!

Attempt 2

As always, we need to optimize the ways ourselves.

Obviously the product is somewhat soluble in the mixed solvent while impurity is much less so.

(NH4)2C2O4 was increased to 2.8g as we now know how to remove the excess.

The same procedure was followed to get and solidify the oil. The first upper layer must be discarded as it contains oxalic acid which is very soluble in EtOH.

Oil was dissolved in 20mL water and 100mL EtOH was added, shaken violently, then the upper layer was filtered with G6 funnel. The oil was again dissolved in 20mL water and 100mL EtOH was added. No oil was released again and this liquid was also filtered. A slightly blue clear extract was obtained.

Filtration was very slow and during filtration the unfiltered liquid also released some oil, some even escaped into the solution, so maybe next time we should wait longer for it to settle. Also the solution already became clear itself during settling, which means...

We still collected the purified solution and let it evaporate naturally though.

It attracted much fruit flies and the dried solution on the wall is not crystal but amorphous sticky cake. Maybe crystallization is simply impossible. Let it go...