Does someone know where can I find instructions for the synthesis of complexes [Cr(H2O)6]3+, [Cr(NH3)6]3+, [Cr(H2O)6]3+ and [Co(NH3)6]3+? Anion in all complexes must be the same.
The first and the third are the same.
You could try to prepare it dissolving Cr(OH)
3 with dilute HCl or dilute H
2SO
4 or dilute HClO4. In the first and second case, some complexes also with Cl
- and with SO
42- can form, after a while; in the third case I assume it doesn't form complexes with ClO
4- but I'm not sure. Anyway, the pH must be ~ in the interval [2;4].
About [Cr(NH
3)
6]
3+ you can make it dissolving Cr(OH)
3 with NH
3 in excess, in presence of some NH
4+ as buffer.
About [Co(NH
3)
6]
3+ you can make it from a salt of Co
2+ with ammonia in excess, letting it oxidise with air: at the beginning it forms the pink [Co(NH
3)
6]
2+ and then the air oxygen oxidise it at the orange-yellow [Co(NH
3)
6]
3+.