Processes for the production of sulphur-containing esters of phosphoric acid and phosphorous acid

An improved process for the production of trithiophosphites, trithiotriphosphates or tetrathiophosphates of the general formula III

• (X).sub.m P(SR').sub.3 (III)
• wherein m is 0 or 1, X represents an oxygen or sulphur atom and R' contains 1 to 24 carbon atoms and represents linear or branched alkyl, alkoxyalkyl, alkylthioalkyl, alkyloxycarbonylalkyl, alkyloxycarbonylcycloalkyl or alkyloxycarbonylaryl;
• or a cycloalkyl, cycloalkylalkyl, aryl or aralkyl group;
• or said group substituted by alkyl, by reacting in a molar ratio of essentially 1 to 3 of (a) a phosphorus trihalide with (b) a mercaptan or thiophenol R'SH to give a trithiophosphite where m is 0, and further reacting the resultant trithiophosphite with an oxygen donor to form the trithiotriphosphate or with sulfur to form the tetrathiophosphate where m is 1, wherein the improvement comprises reacting the phosphorus trihalide (a) with the mercaptan or thiophenol R'SH (b) at a temperature of up to about 150.degree. C. in the presence of 0.005 to 5 mol %, based on component (b), of a catalyst selected from the group consisting of the amines, ammonium salts, aromatic and non-aromatic nitrogen-containing heterocyclic compounds and the salts thereof, the amides of carboxylic and thiocarboxylic acids and of the oxyacids of phosphorus, the guanidines, amidines and azomethines as well as the salts thereof, the sulphoxides, phosphines and phosphonium salts, the phosphine oxides and esters of phosphoric acid.