Dichlorotetrakis(dimethylsulfoxide)ruthenium(II)

Dichlorotetrakis(dimethyl sulfoxide) ruthenium(II) describes coordination compounds with the formula RuCl2(dmso)4, where DMSO is dimethylsulfoxide. Both cis and trans isomers are known, but the cis isomer is more common. The cis isomer is a yellow, air-stable solid that is soluble in some organic solvents. These sulfoxide complexes are used in the synthesis of various ruthenium(ii) complexes. They have also attracted attention as possible anti-cancer drugs.

Structure and synthesis
The cis isomer illustrates linkage isomerism for the DMSO ligand. One of the two dmso ligands that are cis to both chloride ligands is O-bonded while the other three dmso ligands are S-bonded. In the trans isomer, which is also yellow, all four dmso ligands are S-bonded. The cis isomer is formed thermally, and the trans isomer is obtained by UV-irradiation of the cis isomer.

The complexes were first prepared in 1971 by heating DMSO solutions of ruthenium trichloride under hydrogen atmosphere. Modern procedures has been developed which avoids hydrogen gas, either using ascorbic acid or refluxing DMSO to reduce the ruthenium.

Potential applications
RuCl2(dmso)4 was identified as a potential anticancer agent in the early 1980s. Continued research has led to the development of several related dmso-containing ruthenium compounds, some of which have undergone early-stage clinical trials.