DraconicAcid - 6-12-2022 at 13:54
Way back in my youth, we prepared IBr, then reacted that with pyridine to get [I(py)2]Br (I distinctly remember the smell of pyridine, the colour of
the compound, and the TA telling our dumb asses that we had to heat the solution to dissolve the stuff if we wanted to recrystallize it, instead of
just swirling it and staring at it).
I know one of the other courses (that I later TA'd for) also made the acetate, which was more stable than the bromide, but I can't remember how we
changed the counterion. I suspect it was with silver acetate, but I'm hoping to find a less expensive way to change the anion. (The only thing I
remember from that lab was a guy name Wilson, ten minutes after I had stressed that the bromine was to stay in its own fume hood, obliviously carrying
a cylinder full of the stuff to his bench. I wish I had had the courage to throw him out.)
Anyone else have more explicit memories of that reaction? Or a prep that doesn't involve silver?
clearly_not_atara - 6-12-2022 at 21:24
You could possibly use hexammine cobalt (III) acetate. (NH3)6CoBr3 has a very low solubility in water. I don't know many other insoluble bromides --
lead, obviously, but usually people don't want to work with lead.
DraconicAcid - 6-12-2022 at 22:36
I wouldn't be doing this in water- I don't think the stuff is stable in water. I've found preps for the nitrate, perchlorate and fluoborate, all
involving the use of silver salts. Apart from one prep that uses mercurous perchlorate- even worse.
Lots of bromides are insoluble in chloroform or dichloromethane. The trick is finding something soluble enough to do metathesis.
Bedlasky - 7-12-2022 at 07:27
Look at Brauer, page 327-333:
http://library.sciencemadness.org/library/books/brauer_ocr.p...
I2(SO4)3, I(IO3)3 and (IO)2SO4.H2O looks doable, nitrate requires cooling at -78°C in freon as a solvent, perchlorate requires anhydrous HClO4.
Btw. salts containing [ICl4]-, [ICl2]- and [IBr2]- ions also contain iodine in positive oxidation state (III and I) and these can be easily
synthetized.
[Edited on 7-12-2022 by Bedlasky]
DraconicAcid - 7-12-2022 at 10:08
Thanks for the link. I see it's got the silver-based synthesis of the [I(py)2]ClO4.
I've made NEt4[ICl4] (based on Woelen's synthesis of the Cs salt).