Recently, I have answered a question "Comparing explosive properties of mercury(II) cyanate and mercury(II) fulminate" where stability of cyanate vs fulminate was discussed. While I was answering that question, I found out that fulminate vs cyanate stability was previously discussed when chemical isomerism was discovered by Liebig and Wohler. They both reported independently that cyanic acid and fulminic acid that apparently had the same composition had very different characteristics and so they worked on the corresponding silver salts. These two compounds had the same chemical composition, yet are chemically different. Silver(I) fulminate is explosive, while silver(I) cyanate is a stable compound.

My thought process is that since silver(I) cyanate and silver(I) fulminate were extensively discussed to explain chemical isomerism, could that be applied for corresponding mercury compounds i.e mercury(II) cyanate and mercury(II) fulminate so that I could answer the previous question which was specifically asking for the stability/explosive properties of mercury(II) fulminate and mercury(II) cyanate. Mercury fulminate is well known in explosive industry and is used commercially. OTOH, mercury(II) cyanate is not very well known. I could hardly find any information of this compound, So, I assumed (incorrectly?) that mercury(II) cyanate is also unstable since it has not been isolated as a free compound and decompose explosively to a stable compound. Though mercury(II) cyanate is one of the decomposition intermediate of mercury(II) fulminate, I couldn't find any reaction of mercury(II) cyanate reacting or decomposing:

$$\ce{4 Hg(CNO)2 → 2 CO2 + N2 + HgO + 3 Hg(OCN)CN}$$ $$\ce{Hg(CNO)2 → 2 CO + N2 + Hg}$$ $$\ce{Hg(CNO)2 → :Hg(OCN)2}$$ $$\ce{2 Hg(CNO)2 → 2 CO2 + N2 + Hg + Hg(CN)2}$$

Also, I found in some e-books1,2 that $\ce{Hg(OCN)2}$ was apparently called mercury(II) fulminate which is clearly wrong and gave a notion that mercury(II) cyanate never existed/discovered. So, my questions are:

  1. Why is mercury(II) cyanate poorly studied? Has it ever been isolated? Why is it "non-existent"?
  2. Fulminates are even more unstable than cyanates and are considered sensitive compounds and thus difficult to isolate. So, in this case mercury(II) cyanate should be more stable and less sensitive than mercury(II) fulminate and yet the latter compound is studied extensively studied and the former one is yet to be isolated. Why?


  1. Mercury study report to Congress, DIANE Publishing
  2. Accounting for Resources, 2: The Life Cycle of Materials by Robert U. Ayres, Leslie Ayres, Leslie W. Ayres, Edward Elgar Publishing, 25-Nov-1999, Nature, 380 pages
  • $\begingroup$ Sadly no answer to your question but as you did some research on the topic, do you know if something like silver cyanate + mercury(II) chloride has been tested and studied so far? $\endgroup$ – Justanotherchemist Aug 13 '20 at 8:18
  • $\begingroup$ "mercury(II) cyanate should be more stable and less sensitive than mercury(II) fulminate" and therefore so useless that it's totally overshadowed by better known isomer. $\endgroup$ – Mithoron Aug 17 '20 at 0:04
  • $\begingroup$ "The Chemistry of Mercury" by Charles Andrew McAuliffe says only what @Justanotherchemist said + that reaction's in methanol. So, it exists, but people generally don't are about it. $\endgroup$ – Mithoron Aug 17 '20 at 0:19

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