About ten years ago I had an undergraduate student make up a batch of S3N3Cl3 (trithiazyl trichloride, about 10 grams in three separate sealed glass tubes). My intention at the time was that I would use the compound in a simple synthetic sequence that I helped discover.
S3N3Cl3 + 3 AgAsF6 --> 3 AgCl (s) + SNAsF6
8 SNAsF6 + S8 --> 8 SNSAsF6
S3N3Cl3 + 3 AgAsF6 --> 3 AgCl (s) + SNAsF6
8 SNAsF6 + S8 --> 8 SNSAsF6
This was the summer that I was going to bring the plan to fruition and I started the process by getting the sample tubes out of the old storage lockers. In my research group air sensitive compounds such as S3N3Cl3 were stored in sealed glass tubes, wrapped in paper towel and then packed in sturdy cardboard tubes.
Now, these glass tubes were placed in a blue plastic case and moved from ABU to UNB in my car and then kept in my office while I considered when and how I should do some chemistry with them. Late last week I got a call from a graduate student (in the research group that I am now working with) and he said that there had been an explosion in my office. I arrived about 10 minutes later and the top two floors of the chemistry building smelled strongly of sulphur-chlorides (a distinctive smell somewhere between skunk (thiols: LINK) and chlorine. The office itself was filled with a choking fume to the point where I could not enter the office while still winded from running up the stairs. Once we got the windows open and the ventilation fans working this is what I found:
It would appear that over the years a significant amount of the S3N3Cl3 had decomposed.
8 S3N3Cl3 (s) --> 3 S8 (s) + 12 Cl2 (g) + 12 N2 (g)
That kind of decomposition lead to a build-up of pressure in the glass tubes and it is possible that in moving the tubes microcracks in the tubes started to propagate to the point where the glass tubes failed in a spectacular manner. It is true that it is unfortunate that the explosion occurred at all but my oh my, I might have been stunned if I had have been in the office when the tubes exploded and I might have been in worse shape if they had have exploded in my car during transport. There is also the point that I had a tube of S4N4 in the same case (see below). I think that all in all I was lucky.
It all reminded me of 25 years ago when the senior graduate student in the research group that I had joined had a disagreement with me over the nature of my glass tube seal off. I favoured a secure heavy glass seal-off while he favoured a more fragile "elf's cap" seal-off. His comment was that if for any reason the pressure was to build up in the glass tube it would fail at a low pressure. I guess he was right.
I am unaware of any published account of an explosion resulting from S3N3Cl3 decomposition in sealed tubes with time (or for that matter even heat). Makes me wonder about all the other Main group chemists out there that might have similar tubes of similar vintage.
