Abstract: This invention provides a process for the preparation of a complex of the formula L·B·M wherein (a) L is of the formula (R1)(R2)N—(CH2)n—N(R3)(R4), wherein each of (R1)(R2)N and N(R3)(R4) is an optically active amino acid, which may be the same or different; and wherein n is an integer from 1 to 10, (b) B is a base and (c) M is a metal, the process comprising the steps of (i) providing a reaction mixture comprising L and B and having a pH of less than 7.5; (ii) contacting the reaction mixture with M to provide an first complex mixture; and (iii) contacting the first complex mixture with a further amount of B to provide a second complex mixture.