Phosphonothioic dihalides

Also of potential value in synthesis is the halogenolysis process when, depending on reagent (CI2, S02,Cl2, PCI5, SCI2 or S2CI2) and conditions, either phosphonothioic dihalides, RP(S)Cl2. or, tetrahalophosphoranes RPX4 are formed. The action of sulphur... 

Thiohalides of the type RP(S)X2 and R2P(S)X can be made by heating sulphur with the corresponding phosphonous or phosphinous halides. Phosphonothioic (thiophosphonic) halides can be obtained by the action of hydrogen sulphide on tetrachlorophosphoranes (9.425), or phosphonous halide-aluminium trichloride complex (Chapter 6), or P4SJ0 on the corresponding phosphonic dihalide (9.426), or by reaction (9.427) in which PSCI3 acts as a sulphur donor. Monophenyl phosphine and thionyl chloride produce phenyl phosphonothionic dichloride, which can also be obtained by thermal isomerisation (9.428). 

Condensed phosphonothioates can be obtained by direct condensation of phosphonothioic esters with carbodiimide (9.526), or by the action of H2S on phosphonic ester halides (9.527). With phos-phonic dihalides, H2S produces cyclophosphonothioates (9.528). 

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