Dichlorotetrakis(dimethyl sulfoxide) ruthenium (II)

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Dichlorotetrakis(dimethyl sulfoxide) ruthenium (II)

Systematic name	Ruthenium, dichlorotetrakis(sulfinylbis(methane))- (9CI)
Other names	Tetrakis(dimethylsulfoxide)dichlororuthenium(II), Dichlorotetrakis(methylsulfoxide)ruthenium, Dichlorotetrakis(sulfinylbis(methane))ruthenium
Identifiers
CAS number	11070-19-2
Properties
Molecular formula	C₈H₂₄Cl₂O₄RuS₄
Molar mass	484.51 g/mol
Appearance	Various shades of yellow crystals
Solubility in water	water miscible
Solubility	nitromethane, chloroform, dichloromethane
Structure
Coordination geometry	octahedral coordinate
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Dichlorotetrakis(dimethyl sulfoxide) ruthenium (II) describes a variety of chemical isomers with the formula RuCl₂(dmso)₄. These chemical compounds are coordination complexes in which two chlorine atoms and four molecules of dimethyl sulfoxide (dmso) are coordinated to a central ruthenium (II) core. An isomer with this formula was first reported by James et al at the University of British Columbia in 1971, along with a variety of other ruthenium (II) halides.^[1]

These and related dmso-containing ruthenium compounds, such as the phase II trials drug NAMI-A, have attracted attention due to their cancer therapeutic properties.^[2]

1 Structure
2 Synthesis
3 Uses
4 References

[edit] Structure

RuCl₂(dmso)₄ is an octahedral coordination compound. The ruthenium core is in a +2 oxidation state, and the compound follows the 18 electron rule.

The two most relevant isomers are cis, fac-RuCl₂(dmso-S)₃(dmso-O) and trans, mer-RuCl₂(dmso-S)₄. In this notation cis/trans refers to the positioning of the chlorine ligands with respect to each other, whether they are bound adjacently or oppositely. The fac/mer describes the binding of the dmso ligands.

In the cis, fac-RuCl₂(dmso-S)₃(dmso-O) isomer there is an additional aspect to the structure. The notation dmso-S/O refers to the atom through which the dmso molecule is coordinated to the ruthenium center. Thus dmso-S means that the dmso ligand coordinates through the sulfur atom, while dmso-O coordinates through the oxygen atom (in the figure –OS means the same thing as dmso-O, while –SO means the same thing as dmso-S).

The trans, mer isomer results from the dissociation of the weakly bonded dmso-O ligand and the resulting re-arrangement of the compounds geometry. While thermodynamically unfavorable, the trans, mer configuration is kinetically favored. Under UV exposure at room temperature and in the presence of dmso the cis, fac compound isomerizes into the trans, mer form of the compound.

[edit] Synthesis

The original synthesis by James et al involved the dissolution of RuCl₃ in dmso, followed by bubbling of hydrogen gas under heat for 20 hours.^[1]

A simpler and more consistent synthesis was described by Ioannis Bratsos and Enzo Alessio at the University of Trieste. Their procedure to synthesize the cis, fac isomer followed by the trans, mer compound was found to give more consistent results. Commercially available RuCl₃ is dissolved and heated to reflux in ethanol for three hours. The intermediate is isolated, dissolved in dmso and again heated to reflux for two hours after which it is isolated in acetone:^[3]

The trans, mer isomer is synthesized simply by the irradiation of the cis, fac isomer under UV light for four hours or under direct sunlight for six hours:^[3]

[edit] Uses

Several compounds containing ruthenium-dmso complexes have been shown to inhibit or kill tumors. Currently a drug called NAMI-A with the formula trans-RuCl₄(dmso-S)(Im) is undergoing clinical phase II testing for anti-metastasis properties. RuCl₂(dmso)₄ and closely related compounds have also been shown to block tumor growth while showing limited cytoxicity. It is thought that the compound acts through a mechanism that some how interferes with nitrogen oxide pathways in cancer cells. This may be achieved after hydrolysis of the weak dmso-O ligand and rearrangement of the chlorides.^[2]

[edit] References

^ ^a ^b B. R. James, E. Ochiai and G.I. Rempel, Inorg. Nuclear Chem. Letters, 7, 781 (1971)
^ ^a ^b Bratsos, I; Serli, B; Zangranko, E; Katsaros, N; & Alessio, E. Replacement of chlorides with dicarboxylate ligands in anticancer active Ru(II)-DMSO compounds: A new strategy that might lead to improved activity. Inrog. Chem. 2007, 46, pp 975-992
^ ^a ^b Bratsos, I and Alessio E. RUTHENIUM(II)-CHLORIDE COMPLEXES OF DIMETHYL SULFOXIDE. Dipartimento di Scienze Chimiche, Università di Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy