Uploaded April 2017 | Updated September 2026, 1 week ago
In this video we will try to make RuO4, one of the few compounds with an oxidation state of +8. For this RuCl3 is boiled with an excess of Potassium bromate. As the Ru is oxidized the dark colour of the Ru(III) turns into a bright yellow. RuO4 dissolves in water but can be brought into the gas phase by heating it (bp ~40°C). At the end you can see a yellow gas on the top of the test tube (we covered it with a cooling finger to condense it there.
For Ruthenium and Osmium this can be done using common oxidizers for Iron it's a bit more complicated. People sometimes ask why can Os achieve a +8 state...the question is why doesn't Iron do it? Because we base a lot of our chemical understanding on the more common elements like iron we expect anything not reacting like iron would do to be abnormal. In this case however it’s the iron which is behaving rather strange...being one of the only elements in the d-block to not achieve the groups highest (I won't say 'possible' here) oxidation state.
And the answer is a Fe(VIII) although still not really discovered till today is not impossible but the redox potential of Fe(VIII) would be so high that it would oxidize the Oxide-ligands around it to elemental oxygen. So an even stronger oxidizing ligand would be required like Fluorine for example. But Fe(VIII) would also be incredibly small, way smaller than any other highly oxidized element around it and CN=8 coordination is not that common for 3d elements usually. So there is less space and of course the Fluorides would probably repel as well making this probably quite instable, too.
For comparison, the oxidation potential of Bromate to for example Bromide is around 1.4 and Ru(III) to Ru(VIII) is around 1.28 so easiy to do for Bromate. For Iron(III) to Iron(VI) it is around 2.2 already and the highest, Fluorine as oxidat is at around 2.8 so even for fluorine it might become difficult to oxidize Fe(III) to F(VIII) which is why this is quite unlikely to be formed.
In this video we will try to make RuO4, one of the few compounds with an oxidation state of +8. For this RuCl3 is boiled with an excess of Potassium bromate. As the Ru is oxidized the dark colour of the Ru(III) turns into a bright yellow. RuO4 dissolves in water but can be brought into the gas phase by heating it (bp ~40°C). At the end you can see a yellow gas on the top of the test tube (we covered it with a cooling finger to condense it there.
For Ruthenium and Osmium this can be done using common oxidizers for Iron it's a bit more complicated. People sometimes ask why can Os achieve a +8 state...the question is why doesn't Iron do it? Because we base a lot of our chemical understanding on the more common elements like iron we expect anything not reacting like iron would do to be abnormal. In this case however it’s the iron which is behaving rather strange...being one of the only elements in the d-block to not achieve the groups highest (I won't say 'possible' here) oxidation state.
And the answer is a Fe(VIII) although still not really discovered till today is not impossible but the redox potential of Fe(VIII) would be so high that it would oxidize the Oxide-ligands around it to elemental oxygen. So an even stronger oxidizing ligand would be required like Fluorine for example. But Fe(VIII) would also be incredibly small, way smaller than any other highly oxidized element around it and CN=8 coordination is not that common for 3d elements usually. So there is less space and of course the Fluorides would probably repel as well making this probably quite instable, too.
For comparison, the oxidation potential of Bromate to for example Bromide is around 1.4 and Ru(III) to Ru(VIII) is around 1.28 so easiy to do for Bromate. For Iron(III) to Iron(VI) it is around 2.2 already and the highest, Fluorine as oxidat is at around 2.8 so even for fluorine it might become difficult to oxidize Fe(III) to F(VIII) which is why this is quite unlikely to be formed.
![Copper Chemistry: K3[Cu(NO2)5]](https://i.ytimg.com/vi/zz23zENTWXk/mqdefault.jpg "Copper Chemistry: K3[Cu(NO2)5]
Explanation will follow soon")
