You may not have felt the need for a better synthesis of metal azides. Personally, my metal azide requirements are minimal, and very easily satisfied. I can get all I need by looking at a structure drawn on a whiteboard from about twenty feet away, thanks, and have no desire to actually prepare any of these things. I do not see this as an irrational reluctance. For example, last year I wrote about mercury azides, a most alarming class of compounds whose synthesis would be much easier if the two solvent layers didn’t keep getting disturbed by explosions. I’ve also covered selenium tetraazide, a cheerful lemon-yellow solid with the annoying habit of blowing up when it gets warmer than about -64C, which would explain why you don’t run into it very often.
Ah, but perhaps that’s about the change. Thanks to this paper, a collaboration between two groups in Munich (at the TU-München and the Ludwigs-Maximilien-Universität), we now have far easier entry to a wide range of metallic polyazides, oh joy. It turns out that silver azide in liquid ammonia slowly does redox reactions with a variety of other elements, giving a wide variety of otherwise hard-to-obtain compounds. The careful reader will have noted a defect in this scheme: you first have to make a supply of silver azide, which is enough of a show-stopper for me. That Wikipedia article drolly notes that “In its most characteristic reaction, the solid decomposes explosively”, and because it’s a silver salt, that decomposition can be set off by foolhardy behavior like shining a strong light on it.
So there’s your starting material – now let’s use it to make something lively. Shown is a corundum crucible before and after heating up a sample of the manganese azide product (as an ammonia complex). Again, the careful reader will note a crucial detail about the post-analysis state of this labware: it has been blown to hell and gone. This will surely happen to everything in which you heat up samples of metal azides, and believe me, many of these items will be less sturdy than a corundum crucible. Before performing this operation, be sure to ask yourself: “Do I want this apparatus to be blown to pieces?”
And before making the metal azide in the first place, naturally, you need to ask “Do I want to blow myself to pieces?” That’s because this isn’t one of those set-it-and-forget-it Crock-Pot azide reactions. No, you’re going to have to hand-craft these things:
“. . .The reaction mixtures were intensively stirred using a magnetic stirrer when all AgN3 is dissolved (after approximately one day). As long as there is a residue of AgN3, the vessel only should be shaken very gently to prevent silver azide grains to be ground at the glass wall of the vessel.”
Yes, “grinding” is one of those verbs that you don’t want to hear about when azide preps are being discussed, along with “stomping”, “whacking”, “flinging” and several others to which is only response should be “fleeing”. Ah, but once you’ve dissolved that pesky silver azide, the fun is only just coming over the horizon:
“Crust formation occurring at the fluid level and consisting of silver azide at the beginning of the reaction and the respective metal azide at the end of the reaction have to be carefully scraped off the glass every day with a Teflon spatula. The scraping has to be performed with extreme care. . .”
See, I told you that you didn’t want to do this. “Scraping” is yet another one of those verbs that you don’t want to hear brought up in this context. If your touch isn’t quite delicate enough, someone’s going to have to use a larger spatula to scrape you off the ceiling. I note that the experimental section of this paper not only recommends the leather coats that earlier workers in the field have used, but gives suppliers in Berlin and Cologne. And earplugs. And face shields. And helmets. And Kevlar gloves. If scientific meetings were more like fantasy cons, people would be dressing up like this to win prizes.