The invention relates to a method for producing compounds of general formula XPR<2>(OR<1>) (Ia), wherein X represents chlorine, bromine or iodine and R<1> represents an organic radical, by reacting compounds of general formula X2PR<2> (II), wherein X has the above-mentioned meaning and R<2> represents an organic radical, with compounds of general formula R<1>OH (III), wherein R<1> has the above-mentioned meaning, to form a mixture IV, wherein a) the secondary reaction is carried out at a temperature of between 50 to 240 DEG C and at a pressure of 0,001 to 0,9 bar, b) from the mixture IV, the compounds (Ia) are separated from the compounds PR<2>(OR<1>)2 (Ib) and optionally from the compounds II and c) compounds (Ib) and optionally non-reacted compounds II are guided back to the synthesis step.