[shelanachium]

This may be a bit abstruse for a forum like this - if it is can someone recommend a site I could visit? - I am not a professional chemist so cannot access professional sites and many professionals do not answer my emails. I think this is because I do not have an academic email address so my emails go in their spam boxes and are not read. I am however extremely knowledgable indeed and speculate endlessly - like this:

I have often wondered if the extreme compound tetrazomethane NNCNN could be synthesised - if it could it would be an excellent source of atomic carbon in the gas phase at low temperatures, unlike the involatile solid diazotetrazole NN=(CN4).
 
Having learnt of Karl Christe’s synthesis of the azidodiazonium ion [N5]+ I wondered if isoelectronic species could be synthesised such as [NNNCO]+, [OCNCO]+ , [HC(NN)2]+, [HC(CO)2]+ and [NNC(H)CO]+. I have found a paper on the possible stabilities of two of these, [HC(NN)2]+ and [HC(CO)2]+, in which the authors suggest that these should be isolable as solids with suitable counteranions:
 
Papakondylis and Mauridis J Phys Chem A 109 (29) 6549 -6554, 2005. 'Ab Initio Investigation of the Electronic Structure and Bonding of HC(N2)x + and HC(CO)x + cations'
 
[HC(CO)2]+ should be obtained on superacid protonation of carbon suboxide C(CO)2, but [HC(N2)2]+ might be obtained by a similar method to that Christe used for [N5]+ which is the reaction between azide ion, dinitrogen difluoride and arsenic pentafluoride:

[N3]- + N2F2 + 2AsF5 ---> [N5]+ + 2[AsF6]-

 but substituting diazomethide anion for azide:

[NNCH]- + N2F2 + 2AsF5 ---> [NNC(H)NN]+ + 2 [AsF6]-  (NNC(H)NN same as [HC(N2)2]+)

 A third ion they do not discuss is [NNC(H)CO]+ which is protonated diazoketene - might diazomethide/ COF2/AsF5 produce this?

[NNCH]- + COF2 + 2AsF5 ---> [NNC(H)CO]+ + 2[AsF6]-

Then [NNC(H)CO]+ + base ---> [baseH]+ + NNCCO (diazoketene)
 
[HC(N2)]+ if preparable as salts should likewise yield tetrazomethane with base; this should be a gas or highly volatile - if it does not at once decompose! It would presumably be prepared in a stream of argon or nitrogen gas to dilute it and reduce explosion risk, and could perhaps be used to grow further diamond on a diamond substrate, with no atoms other than C being incorporated. Whether these would prove cheaper than natural diamond might be disputable!

[hmx9123]

Tetraazidomethane was prepared recently by a German research group.  (Angew. Chem. Int. Ed., 2007, 46, 1168-1171).  Though it isn't the same thing, it is similar.  Christie did a lot of earlier work with the triazidocarbenium cation.  What you propose may be possible, but the route to get there is tricky.  It is the same problem with many unstable energetic compounds.  The conditions traditionally used to produce such materials are generally untenable as they have conditions that are deleterious to the product.  The product must also be kinetically stable, not decomposing at the drop of a hat into nitrogen and whatever other products, though in your case, that doesn't seem to be as large a problem (this is more a problem with the high-nitrogen materials that Christie works with).  I would not doubt it in the least if people have tried to make these materials before and failed.  Have a good hard search on SciFinder.

Also, would the compound name be tetraazomethane, or bis(diazo)methane?

[HEDM]

Its true these compounds have very high energy due to the azide groups. C(N3)4 Have 93% nitrogen while being extremely sensitive to stimulus such as impact (not even impact, feather is enough to set it off) Whats more, this compound have a very bad density due to its un-symmetrical shape and bad crystal packing. Therefore there is no point in making energetic materials such as this one.

However if you just go down a little bit, 91.5% Nitrogen content, we have beautiful compounds such as hydrazinium azide hydrazinate. N2H5+ N3- N2H4. While this compound burns to produce only water and nitrogen, and is also insensitive to impact and friction.

Furthermore, if you're talking high nitrogen materials, dihydrazinium bistetrazolylamine have a detvel of nearly 10kms, while being much less sensitive and easier to make. TKX50 even less sensitive than TNT posses detvel of 9700 and as much det pressure as CL-20.