The invention relates to the acyl- and bisacylphosphine derivatives according to formula (I), wherein Y represents O, S, NR.sup.3, N--OR.sup.3 or N--NR.sup.3R.sup.4, Z represents O, S, NR.sup.3, N--OR.sup.3, N--NR.sup.3R.sup.4 or a free pair of electrons, and FG represents a leaving group and the remaining groups are defined as in the description. The invention further relates to a method for the production of the inventive derivatives and to their use. ##STR00001##