Blue Acid Chemistry (5): K3[CoBl6]

Я буду жить теперь по-новому

Мы будем жить теперь по-новому

——Люберцы by Lube

OK, let's be serious... as it is the real, first battle!

Co2+ + 2Bl- = CoBl2

CoBl2 + 3Bl- = [CoBl5]3-

2[CoBl5]3- + O2 = [Co2O2Bl10]6-

[Co2O2Bl10]6- + 2Bl- + 2H2O = 2[CoBl6]3- + H2O2 + 2OH-

Net: Co2+ + 6Bl- + 1/2O2 + H2O = [CoBl6]3- + 1/2H2O2 + OH-

Dissolve 4.0g(0.01mol) (NH4)2[Co(H2O)6](SO4)2 and 1.3g(0.02mol) KBl separately, and mix together. Solution turned into a brown milk of CoBl2.2H2O(?) immediately.

However, it was found that it is not precipitation, but colloid, presumably due to the existence of ammonium in source material. Ammonia can be smelled but the solution is nearly neutral.

We tried to heat but it just turned red, and is still colloid.

Addition of ethanol finally turned it into a greenish blue solid, probably anhydrous CoBl2, which can be slowly filtered.

The solid was thrown into water to dissolve sulfates in it, and then filtered again and washed thoroughly with water.

Then, it was thrown into water again, and 2.8g(0.043mol) KBl was added. A little excess is needed to prevent formation of green precipitation K2Co[CoBl6](?), according to synthesis manuals. Solution turned orange. This should be mainly K3[CoBl5], its dimer K6[Co2Bl10], and some oxidized K6[Co2O2Bl10]. Detailed composition doesn't matter.

Solution was boiled for 20min, and color gradually disappeared, due to oxidation and substitution. Final solution is slightly yellow, and is extremely basic. Some unknown precipitation appeared.

Filter when it's hot, and then add ethanol to precipitate the product, which is a yellow solid. Yield 1.5g(45%). Loss might be due to the CoBl2 that bypassed filter and the unknown precipitation. Also we should concentrate solution as (6) said.

All in all, we made it...