Phosphinothioic and Phosphonothioic Acids

R2PH + 2S + NH4OH R2P(S)SNH4 + HjO Ph2PSCl + NaSH Ph2PSSH + NaCl P4S,o + 8QH — 4Ph2PSSH + 2H2S 

Some of the acids are crystalline, while others can only be obtained as uncrystallisable oils. They are generally not very stable and decompose gradually at room temperatures with the evolution of hydrogen sulphide. Their salts are relatively stable, however, particularly those of (CF3)2P(S) SH. The acids are strong and their pK, values (in 7% EtOH), are only slightly dependent on the nature of R (cf. phosphorothioic adds above)  

These acids, except (Cp3)2PSSH, have a strong tendency to form hydrogen-bonded dimers in concentrated solution, in the melt (9.437) and in solid state (Chapter 13.1). 

Oxidation is easily effected with hydrogen peroxide, nitric acid, alkali-bromine and so forth, to form the corresponding phosphinic acid R2P(0)0H (Chapter 6). Treatment of sodium salts with iodine and aqneous potassinm iodide yields phosphinothioic disulphides. 

The action of chlorine on diphenylphosphinodithoic acid is to produce a halophosphorane (9.439), and phosphinothioic chlorides can be obtained with hydrogen chloride or phosphorns pentachloride (9.429). 

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