abstract |
A mixture M includes at least one compound A, selected from (a1) a compound of the general formula (I) and/or (a2) a compound of the general formula (I′), at least one compound B, selected from (b1) a compound of the general formula (II) and/or (b2) a compound of the general formula (II′) and/or (b3) a compound of the general formula (II″), and at least one compound C, selected from cationic germanium(II) compounds of the general formula (III). |