Abstract: A process for the preparation of a complex of formula (I): the process comprising the step of reacting a complex of formula (II) or a complex of formula RuX3.H2O (IV) with a bidentate ligand of formula (III) wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, A, B, and X are described in the specification; the molar ratio of the complex of formula (II): the bidentate ligand of formula (III) is about 1:6 to about 1:8 or the molar ratio of the complex of formula (IV): the bidentate ligand of formula (III) is about 1:3 to about 1:4; and the process is carried out in water or a water-based solvent, wherein the water-based solvent comprises at least 60% water (by volume) and an organic solvent, at one or more temperatures in the range of about 80° C. to 110° C.