ferrocene2

I raised the question again a few weeks ago.

If it wasn't iron (VIII) in the accounts above (see post of Monday at 6.35) then what was it? In the original post, I quote Mellor who describes how (what he says was) barium perferrate and the other iron (VIII) compounds were obtained. I've said numerous times in these exchanges that there are many mistakes in Mellor's work (but Wikipedia isn't error free either).

I was not in a position to analyse the product - I was a schoolboy trying out on the kitchen table something I'd read which intrigued me - and still does. I am reporting what was written in Mellor's book and what I found. Of course I'm aware that chemistry has moved on and that there are countless compounds that have been produced that people hadn't even dreamed of. And, yes, he made mistakes - some of which I mentioned previously e.g. OsF8 doesn't exist and PbF4 does - and so do many other transitional metal fluorides which didn't receive a mention. Who'd have predicted in the 1930s the existence of xenon compounds including some of Xe(VIII)?) What I am asking - and have yet to receive an answer to - is what was going on in Mellor's report and what was the bright green melt in the possible (and I emphasise the word possible) equation - and I cannot think of any iron compound which could behave in this way: 5KNO3 + Fe203 + 4KOH = 5KNO2 + 2K2FeO5 + 2H20 If you don't know - as appears to be the case - and/or aren't in the position to try the experiments described, just say so. I well remember Cotton and Wilkinson although I no longer have a copy. Were they aware, I wonder, of Fe (-II) and Fe (0)?

Studiot: I joined many years ago using the name "ferrocene". I re-joined yesterday using the name "ferrocene2" as I couldn't log-on using my previous name. And, yes, I realise that Mellor died many years ago but I first came across his work in the late sixties at Manchester Public Library (the round building) where all volumes were freely available for reference. If he was completely wrong about iron (VIII) and the perferrates - which he may well have been - can anyone explain what may have been going on or account for my own observations which were not quite the same as he described? I am no longer in a position to repeat the experiments outlined but other people must be. (As for the compound ferrocene itself, I studied it at (BSc) degree level in 1971-72)

Some years ago, I created a topic about the existence or otherwise of iron (VIII). What follows is an update after I was able to download as a pdf all but one volume of J. W. Mellor's "A Comprehensive Treatise on Inorganic and Theoretical Chemistry". In Volume XIII Fe (Part II) on page 936 it says: O. Baudisch and P. Mayer 2 assumed that perferric acid, FeO3(OH)2, or H2FeO4 [it means H2FeO5], is produced when freshly precipitated ferrous hydroxide is oxidized by oxygen. D. K. Goralevich said that iron tetroxide, or perferric anhydride, FeO4, or perferric acid, H2FeO5, is probably formed as a volatile, unstable compound when barium perferrate, BaFeO5, is treated with an excess of dil. sulphuric acid, at a low temp. Perferric anhydride is insoluble in water, but soluble in dil. acids. He prepared bright green potassium perferrate, K2Fe05.nH20, by fusing ferric oxide with potassium hydroxide and an excess of potassium nitrate, or, better, chlorate. The salt can be purified by sublimation; it decomposes very slowly "when kept in air; explosively, when warmed, on treatment with conc. sulphuric acid, or on impact if mixed with sulphur, phosphorus, or charcoal. It is quite stable in alkaline soln., but acids readily decompose it with evolution of oxygen and, in the case of hydrochloric acid, chlorine. Oxidizing agents like chlorine and hydrogen peroxide give a deep red soln. of potassium ferrate, with evolution of oxygen. Neutral soln. of the perferrate give no reaction for ferric ions until, on the addition of acid, decomposition has commenced. Similarly with sodium perferrate, the alkaline earth perferrates were obtained as white precipitates on adding a soln. of a salt of an alkaline earth to a soln. of potassium perferrate ; with barium salt, barium perferrate, BaFeO5.7H2O, is produced; and with a strontium salt, strontium perferrate, SrFe05.7H20. These salts are white and insoluble in water, alcohol, and ether. This is all it says on Fe (VIII) despite devoting six pages to Fe (VI). Questions: 1 Does Fe (VIII) exist? If it did, one might it to be less stable than Ru (VIII) and RuO4 isn't very stable. Going across the period from Sc - Ni, Ti (IV) and V(V) are stable, Cr (VI) less stable than Cr (III), Mn (VII) less stable than Cr (VI), and Fe (VI) pretty unstable unless dry and stored in the absence of moisture and CO2. 2 Were all these observations wrong? As I wrote previously "I remember clearly that a dark green melt was produced, that it turned white when it cooled and solidified. [I also noted that water had no obvious effect] all contrary to what Mellor said. I cannot think of any iron compound which would behave in such a way under those conditions. There are a number of iron compounds which are white, but I can't think of any which would fit this particular bill". 3 Mellor has numerous errors. For example, it describes the properties of OsF8 which we know doesn't exists; the perbromates and PbF4 didn't exist according to Mellor although we know they do. 4 Is anyone in a position to try these experiments? I performed them as a teenager in 1968 when I could easily get hold of the chemicals in question.