The title complex can be obtained from hydrated RuCl3 in three steps. Commercially available ruthenium trichloride is first reacted with a warm mixture of DMSO and HCl to give (DMSO)2H[trans-RuCl4(DMSO)2], which is then transformed into the corresponding sodium salt. The latter is reacted with imidazole in DMSO/acetone to give Na[trans-RuCl4(DMSO)(Im)]2DMSO. Acetone and, sometimes, water molecules can partially replace the DMSO molecules of crystallization.