Synthesis, molecular structure, and chemical behavior of hydrogen trans-bis(dimethyl sulfoxide)tetrachlororuthenate(III) and mer-trichlorotris(dimethyl sulfoxide)ruthenium(III): the first fully characterized chloride-dimethyl sulfoxide-ruthenium(III) complexes

Abstract

The synthesis, molecular structure and chemical behavior of two chloride-dimethyl sulfoxide-ruthenium(III) derivatives, namely [(DMSO)2H] [irarts-Ru(DMSO)2Cl4] (1) and mer-Ru(DMSO)3Cl3 (2), are reported. They represent the first examples of fully characterized halogen-dimethyl sulfoxide-ruthenium(III) complexes. Further relevance in their synthesis comes from the known antitumor properties of isostructural Ru(IIl) complexes with heterocyclic nitrogen ligands and of halogen-dimethyl sulfoxideruthcnium(ll) complexes as well. The crystal structures of 1 and 2 have been determined by three-dimensional X-ray analyses.Crystal data are as follows: [(DMSO)2H] [r/-ans-Ru(DMSO)2Cl4], monoclinic, space group Pl/n, a = 9.273 (1) Á, b = 16.509 (3) Á, c = 14.023 (3) Á, ß = 100.79 (2)°, Z = 4, R = 0.041; for mer-Ru(DMSO)3Cl3, monoclinic, space group /'2,/c, a = 10.105 (2) Á, b = 13.832 (3) Á, c = 11.115 (2) Á, ß = 94.39 (2)°, Z = 4, R = 0.028. In 1 there are two crystallographically independent [Ru(DMSO)2C14]" anions lying on crystallographic 2-fold axes, passing through Ru and two trans Cl atoms, so that the other two Cl atoms and the two S-bonded DMSO molecules are also trans to each other. Cations are provided by protonated DMSO molecules, [Me2SO-H-OSMe2]+. In 2 the three chlorine atoms are in the mer configuration, and the two trans DMSO molecules arc S-bondcd to Ru, while the third one is O-bonded. Both complexes are intermediates in the synthesis of cis-RuCl2(DMSO)4 front hydrated RuC13. Cyclic voltammetric evidence shows that, in dimethyl sulfoxide and dichloromethane solution, 2 is in equilibrium with an isomer that very likely differs in the coordination mode of one DMSO (S-to O-bonded isomerization). The chemical behavior of 1 and 2 in aqueous solution has been studied at low pH (<3), where the formation of polymeric species is prevented. When dissolved in water, both complexes rapidly release one of the two trans S-bonded DMSO's and, in about 24 h at room temperature, produce the same neutral species: mer,m-[RuCl3(H20)2(DMS0)]. A completely similar behavior is

1H NMR study of the solvolysis of the paramagnetic tetrachloro-bis(imidazole)ruthenium(III) anion in water, methanol, and dimethyl sulfoxide

“…Peak doubling due to the presence of both coordinated and protonated imidazoles is no longer present. The u(S-0) mode of DMSO is identified at 1057 cm-', in agreement with S-bonding (27,31). A hydrogenbonded u(N-H) band is also,seen at 3242 cm-'.…”

“…Small electron density residuals in the solvent region suggested partial replacement of DMSO by acetone in the structure. A similar problem has been encountered for related compounds (14). The coordinates and interatomic distances are given as supplementary materiaL3 So far, we have been unable to grow better crystals.…”

“…When this work was undertaken, 'H NMR spectra had been reported for aqueous solutions of [Ru(NH,),Im]Cl,, used as a model for ruthenium-histidyl protein complexes (13). More recently, the spectra of (ImH) [RuC1,1m2] in DMSO (10) and of Na[RuCl,(DMSO)Im] in D,O (14) were reported.…”

“…The contribution of If has increased to 15%, whereas another diamagnetic species l g (6 12.9 (N-H) (27). Reduction of Ru(II1) to Ru(I1) is known to take place readily when more than one n-accepting sulfoxide ligand is coordinated, and the complex becomes increasingly reducible with each new DMSO ligand introduced in the coordination sphere.…”

Anticancer activities of the ruthenium carboxylato, amido and pyridine complexes

“…Clearly, ruthenium complexes represent a new class of compounds endowed with antitumor activity (1,22). Two ruthenium complexes NAMI-A and KP1019 are already in clinical trials (23)(24)(25)(26)(27). Ruthenium complexes are rich in chemistry and the side-effects of the ruthenium complexes are low compared to platinum-derived drugs because of the selective activation to cytotoxic species in solid tumor tissues (28).…”