Energetic salts of cubane

Greetings,
As you may know I‘m currently doing quite a bit of work on cubanes, documented on this forum as well (https://www.sciencemadness.org/whisper/viewthread.php?tid=16...), and while my primary focus is on pharmaceuticals I couldn’t do but at least do some test in regards of energetic derivatives; in the future I‘m planning to make di- and tetranitfocubane too but that’s a different story for now.
Even simple seemingly non-energetic derivatives of cubane do at times actually have energetic properties, with detonation of dimethyl cubane-1,4-dicarboxylate having been reported on kugelrohr distillation (https://apps.dtic.mil/sti/tr/pdf/ADA210368.pdf), and the 1,4-dicarboxylic acid kind of deflagrating on rapid indirect heat, with a more impressive result potentially being achievable by confining the solid though I didn’t try.
The fact that the diacid does already exhibit some sings of energetic properties raises the question whether this could potentially be improved by preparing the corresponding carboxylate heavy metal salts, and from this further optimized by adding oxygen containing ligands may be imaginable though I don’t have any concrete plans in that regard yet.
It is worth noting that the following two compound to my knowledge have not been reported in literature before. For the silver salt there is the concern of rearrangement to the corresponding cuneane (https://pubs.acs.org/doi/10.1021/jacs.3c03207), but without heating and as a solid salt this process can be expected to be reasonably slow if not completely nonexistent.

Cubane-1,4-dicarboxylic acid copper(II) salt:
In a 20 ml glass vial 96,1 mg of cubane-1,4-dicarboxylic acid (0,5 mmol) where dissolved in exactly 1 ml of 1 molar sodium hydroxide solution, measured out with the help of an eppendorf pipette, and the yellowish solution further diluted with 0,5 ml of water. A random excess of a reasonably concentrated copper(II)-chloride dihydrate solution was added, instantly resulting in a teal precipitate, which was collected by gravity filtration and throughly washed with dest. water. After drying over silicagel under vacuum 136,1 mg of a teal amorphous solid were collected, corresponding to a 107,2% yield assuming the anhydrous salt, though as its likely present as a hydrate of unknown composition it‘s hard to state a proper yield.
This material is insensitive to shock and friction and on rapid indirect heating only combusts with an bluish red flame, surprisingly leaving little residue. On confining in aluminum foil, ~40 mg tested, a surprisingly strong detonation with a very sooty flame could be perceived, ripping multiple holes into the aluminum foil below though not resulting in much shrapnel.


Fig.1-2 Suspension of the product and the dried copper salt

Attachment: 20250622_215524.mp4 (3.6MB)
This file has been downloaded 103 times
Fig.3 Indirect flame test of the copper salt

Attachment: 20250622_220218.mp4 (4.2MB)
This file has been downloaded 92 times
Fig.4 Test of 40 mg of the confined copper salt

Cubane-1,4-dicarboxylic acid silver(I) salt:
Because of the general tendency of silver salts to be fairly light sensitive all of the following work was conducted under a source of red light and silver containing glassware wrapped in aluminum foil when possible.
In a 20 ml glass vial 96,1 mg of cubane-1,4-dicarboxylic acid (0,5 mmol) where dissolved in exactly 1 ml of 1 molar sodium hydroxide solution, measured out with the help of an eppendorf pipette, and the yellowish solution further diluted with 0,5 ml of water. A solution of around 250 mg silver nitrate (1,47 mmol) in a minimal amount of water was added, and the resulting grayish precipitate collected by vacuum filtration and throughly washed with dest. water. After drying over silicagel under vacuum 176,7 mg of a light grey solid were collected, corresponding to a percent yield of 87,1%.
This material can actually be detonated by strong shock from a hammer, though I still didn’t notice any friction sensitivity. On indirect heating the material deflagrates with a pop, may even call it at least a partial weak detonation, leaving behind a black residue likely consisting of carbon. On confining in aluminum foil, again ~40 mg wer tested, the material detonates with a sharp bang releasing a large amount of soot and ripping a large hole around 5 cm in diameter into the aluminum foil below, fragmenting most of the foil into some very fine shrapnel.


Fig.5 The dried silver salt

Attachment: 20250623_202419.mp4 (2.8MB)
This file has been downloaded 73 times
Fig.6 Indirect flame test of the silver salt

Attachment: 20250623_202950.mp4 (5.8MB)
This file has been downloaded 93 times
Fig.7 Test of 40 mg of the confined silver salt