Formula: [NH3]4Cu[NO3]2
detonation velocity:
3500 m/sec

As you can see in the first link, moist crystals of tetraamine copper nitrate (TACN) in a glass tube under flame first seem to melt, then instantly decompose in an explosive exothermic reaction (not actually a detonation as the thin glass does not shatter)

The poster of this video claims that it can be detonated with only 0.5g HMTD, from the damage caused by the detonation of 100g TACN, it seems much more sensitive to high order detonation than ammonium nitrate mixtures.

Here are some pictures of TACN deflagrating. The salt easily ignites from the flame of a butane torch. TACN rapidly deflagrates with greenish-blue flare, but there does not seem to be the instant "poof" which is seen with the deflagration of most other primaries:


Edit: the poster appears to have removed the above two videos

There is also a video for tetraamine copper permanganate:

and tetraamine copper persulfate:

Both of these last two complex salts are much more sensitive, (and probably unstable for long-term storage) than the nitrate.

I think I read somewhere that tetraamine copper nitrate is actually fairly insensitive to mechanical impact, that reliable detonation of this salt requires another primary. TACN is supposedly also very hygroscopic, and if not free from moisture can be difficult or impossible to ignite. If preparing the salt for the purpose of deflagration/detonation, pure methanol should be used as the solvent, with dry ammonia gas bubbled in, so that the product will be free from traces of water.

"I can light it with difficulty. If I put a flame of a torch on it, then it first melts and then I get kind of 'poof' with a small cloud of black smoke. It does not really explode, it is more like nitrated cotton-wool, but with a less visible flame." (woelen)

"the problem (from an energetic aspect) is going to be hydration." (Axt)

"Yesterday i tried to make TACN by dissolving 2g pure copper and 5g ammonium nitrate in 10ml 10% ammonia sulution.
After 1 day the solution turned blue and bright blue crystals formed at the copper. I filtered the solution and ended up with 0.7g with crystals. I dried them well. Then i tried to detonate it. It got a very little "poof sound" and some smoke came. I also tried to use CuO insted of pure copper. I ended up with some very dark blue\purble crystals after i filtrated it. When i heated them up, nothing happend." (mikkello, who is from Norway)

"TACN is easily dehydrated in dry acetone, forming a stable dull-violett powder. Put the crystals in a beaker filled with dry acetone, crush them carefully, stirr and let it sit for a short time. The acetone will take up the water of crystalization. Pour off the acetone (which now contains water) and wash with another portion. Repeat until the color of the crystals no longer changes. Of course this works best with dry reagent grade acetone, but I tried it with the crappy comercial stuff (which contains a considerable amount of water) and even that worked fine. Then decant and press dry between filter paper. Let the crystals dry in warm air until all acetone has evaporated. Then do a final drying over CaCl2. During the acetone wash you will notice the chunky crystals change color from deep blue to a light violet and turn into a fine powder. This powder is stable in air and quite powerful. Its quite sensitive too - smack with a hammer and it goes boom. This is the only useful form of TACN. The hydrated form cannot be stored because it readily draws CO2 from air. It is also very insensitive and weak. I observed the same effect with TACP: The hydrated form is useless. It can hardly be ignited with a match and is very insensitive to impact. Remove the water of crystalization and you get a much more sensitive and powerfull substance. Of course these materials must be stored in a well stoppered bottle to exclude moisture. From the hydrated form of TACN you will hardly get anything more impressive than a pop sound and some smoke." (edited compilation of quotes from Taoisearch)

it should actually be considered a primary explosive, although it seems less sensitive than many other primaries, but it can be difficult to reliably initiate. If free from water, it will deflagrate if subjected to the intense flame of a butane torch. Like other primaries, the deflagration likely will lead to detonation if the mass of TACN is more than a few grams and there is a small degree of confinement, such as in a little rolled up paper tube.

The main problem seems to be hydration. Although the crystals of TACN may appear dry, it is quite likely that molecules of water become incorporated into the solid crystal structure. CuSO4 is known to form such a solid hydrate CuSO4*(5)H2O. For reliable use as an explosive, TACN needs to be prepared without water, and be kept away from long exposures to air.

Anhydrous Cu(NO3)2 is apparently very reactive;

"at temperatures below –5°, the reaction of diethyl ether with copper(II) nitrate yields exclusively gaseous ethyl nitrite and complexed acetaldehyde. At higher temperatures, the acetaldehyde is further oxidised to acetate, with liberation of gaseous NO and NO2"
Anhydrous copper(II) nitrate as an oxidising agent. L. C. Coard and R. E. Powell
J. Chem. Soc. A, 1967, 296-297