Tetrathiophosphoric acid

Phosphoranyl radicals can be involved [77] in RAFT processes [78] (reversible addition fragmentation transfer) used to control free radical polymerizations [79]. We have shown [77] that tetrathiophosphoric acid esters are able to afford controlled/living polymerizations when they are used as RAFT agents. This result can be explained by addition of polymer radicals to the P=S bond followed by the selective p-fragmentation of the ensuing phosphoranyl radicals to release the polymer chain and to regenerate the RAFT agent (Scheme 41). 

A problem that would arise with the general use of the prefix variant of functional replacement names is illustrated by the thio acids. The names trithiocarbonic acid, tetrathiophosphoric acid, etc., would lead to anion names trithiocarbonate, tetrathiophosphate, etc., which appear to be additive names but are incorrect as such because the ligand prefix is now sulfido or sulfanediido [thus giving trisulfidocarbonate(2—),tetrasulfidophosphate(3—), etc.]. Section P-65.2 of Ref. 1 prescribes the infix-based name carbonotrithioic acid, leading to the anion name carbonotrithioate, which will not be mistaken for an additive name. 

Simple salts of all the ortho ions (9.375) are known and in the absence of any restricting conditions, resonance of the double bond is assumed to occur with all four linkages. The successive introduction of the S atom leads to an increasing hydrolytic instability (9.376), and acids or salts with these anions are generally not easy to prepare. Phosphoromonothioic (monothiophosphoric) acid is the most stable, and phosphorotetrathioic (tetrathiophosphoric) acid is the least Solutions of the acids in Equation 9.376 can be prepared by acidification of heavy metal salts. The latter are prepared by precipitation from solutions of their sodium salts with the appropriate metal salt. 

Without additional reagents Tetrathiophosphoric acid esters from alcohols... 

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