Bisacylphosphine oxide or bisacylphosphine sulfide compounds of formula (I) or (II) wherein R1, R2, R3, R1a, R2a and R3a independently of each other are C1-C4alkyl, C1-C4alkoxy or halogen; X is O, NR5 or S; or, if R4 is Cl, F or Br, X is a direct bond; Y is O or S; n is 1 or 2; R4, if n is 1, for example is hydrogen, (CO)R6, (CO)OR6, (CO)NR5R6, (SO2)—R6, C1-C28alkyl, R4, if n=2, is for example C1-C18alkylene; R5 is for example hydrogen, or C1-C12alkyl; R6 is for example C1-C12alkyl; R7, R8 and R9 independently of each other for example are C1-C4alkyl; R10 is for example C2-C18alkylene; X1, is O or S; m is 1, 2 or 3; Q represents one or two inorganic or organic cations with a charge of m+; are suitable photoinitiators, available by a claimed process.