Patent ID: 8846921

Claim:
A process for preparing at least one metal complex of the formula (2) [M a L x X n ]Y m (2) where M is a metal selected from the group consisting of Mn(II), Mn(III), Mn(IV), Fe(II), Fe(III) and Fe(IV), X is a coordinating compound selected from the group consisting of singly, doubly and triply charged anions and uncharged molecules capable of mono-, bi- or tridentate coordination to a metal, Y is a noncoordinating counterion which ensures the charge balance of the complex, a is 1 or 2, x is 1 or 2, n is a number from 0 to 4, m is a number from 0 to 8, and L is a ligand of the formula (1) or the protonated or deprotonated form thereof where R is hydrogen, hydroxyl or C 1 -C 4 alkyl; R 1 is C 1 -C 4 alkyl, C 6 -C 10 aryl, pyridinyl-C 1 -C 4 -alkyl or (CH 2 ) k N(C 1 -C 4 -alkyl) 2 ; R 2 is C 1 -C 20 alkyl, C 6 -C 10 aryl or pyridinyl-C 1 -C 4 -alkyl; R 3 is C 1 -C 4 alkyl; z is C═O or C(OH) 2 and k is a number from 1 to 6, comprising the steps of (i) preparing a solution or suspension of at least one ligand of formula (1) in acetone; (ii) preparing an aqueous metal salt solution of an iron or manganese salt; (iii) contacting the solution or suspension of at least one ligand of formula (1) in acetone with the aqueous metal salt solution of the iron or manganese salt; and (iv) reacting the at least one ligand of the formula (1) with the iron or manganese salt in an acetone/water mixture wherein the temperature range is from 0 to 50° C.