This is really two questions. I'm trying to convert P-S bonds into P-N bonds using Ag+ to pull off the sulfur, but when attempting the reaction in THF, either the silver sulfide was dissolved in the solvent, or it was suspended in particles so finely that they would not precipitate out.
Then meanwhile, I'm expecting P-N double bonds and P-N single bonds in my product, but there is a near-total lack of publications stating what 31-P NMR signals confirm the presence of those bonds. Or do I need to use IR to show those are present?
Also to further complicate things, the P-N bonds that form are water-sensitive - water will kick off the amine N, protonate that, and form phosphine oxide.
Dear Jason Wilt, first of all it would be interesting to know if you followed a literature preparation. Where does the nitrogen in your reaction come from?
Besides, I have two answers:
1. Silver sulfide is not soluble in any organic solvent.
2. 31P NMR is certainly well suited to characterize your products. If you check out RG for the term "phosphorus-nitrogen bond" you will find numerous references describing the synthesis and characterization of such compounds.
Frank T. Edelmann The preparation is partially based on literature and partly not. The nitrogen source was aniline, and the silver salt was AgBF4.
If they are not soluble in solution, then how would I go about removing them? I tried filter paper & celite plugs but had limited success.
The literature this is based on uses the above silver salt and various amines to convert C-S double bonds to C-N double bonds.
Dear Jason Wilt , I'm not sure if such a reaction can be transferred from C–S to P–S systems. Are there any precedents in the literature? Did you observe a dark (black) color indicating the formation of silver sulfide?
Yes, whole solution turned black & black color was not effectively filtered out by filter paper or celite. There was a little grey-black powder on the celite & on the filter paper, but the liquid that went through was still brownish-black (color of black coffee).
Also no, there aren't really any literature precedents.
Dear Jason Wilt, I'm afraid that it is perhaps a bit too courageous to assume that a reaction that works with C–S bonds can be done in the same way with P–S compounds. In the phosphorus system you have the possibility to form P-coordinated complexes with Ag+.
BTW If someone helps you by answering your questions on RG it is polite and generally accepted to recommend those answers....
Frank T. Edelmann I did see all the reactant compounds get consumed on 1H & 31P NMR, but due to Covid-induced workday restrictions & having no idea how to purify the crude, the crude sat in my fume hood for a while. When I checked it again on NMR, the signals from the aniline NH2 reappeared, suggesting that trace water vapor was decomposing P-N double bonds into phosphine oxide & the amine.
Also, my bad, this is my first-ever question asked on this website.
Dear Jason Wilt, thanks for the information. That sounds reasonable. P–N-bonded compounds are often very moisture-sensitive, and phosphine oxides are formed rather readily. Hope you can be back in the lab soon and try the reaction again. Good luck!
Frank T. Edelmann Would starting w/ a P-S compound that's already in its +5 oxidation state using excess amine help prevent formation of Ag+P- complexes, or are they inevitable to form?
The first attempt used stoichiometric amounts of all necessary reagents.
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