Provided herein is a process for preparing triaryl organoborates proceeding from alkyl or cycloalkyl boronates in the presence of an n-valent cation 1/n Kn+ to obtain organoborates of the formula 1/n Kn+R34B−—R1 (IV), where one equivalent of organoboronic ester of the formula B—R1(OR2)(OR3) (I) is initially charged together with 1/n equivalents of salt Kn+ nX− (II) and 3 equivalents of metal M in a solvent or a solvent mixture, 3 equivalents of a haloaromatic R4—Y (III) are added, and optionally a second organic solvent water is added and the compound 1/n Kn+ R24B−—R1 (IV) is separated off with the organic phase, and to the use of these substances as co-initiator in photopolymer formulations.