Poly[μ3-chlorido-μ2-chloridodichlorido(μ-dimethyl sulfoxide-κ2 O:S)(dimethyl sulfoxide-κO)(μ-pyrimidine-κ2 N:N′)ruthenium(III)sodium]

The title complex, [NaRuCl4(C4H4N2)(C2H6OS)2]n, is the sodium salt of monoanionic octahedral [RuIIICl4(pyrimidine)(DMSO)]− in which the sulfur-bound dimethyl sulfoxide (DMSO) and pyrimidine ligand are oriented trans to one another on the RuIII atom. The average of the four Ru—Cl bond lengths is 2.355 (15) Å, and the Ru—S and Ru—N bond lengths are 2.2853 (3) and 2.1165 (11) Å, respectively. The complex forms a chain, with a six-coordinate sodium ion bridging the ruthenium(III) units. The sodium cation is coordinated by cis-chloride ligands on ruthenium [Na—Cl = 2.9576 (7) and 2.6988 (7) Å], chloride and DMSO ligands from the ruthenium complexes related by inversion [Na—Cl and Na—O = 2.8888 (7) and 2.2623 (12) Å, respectively], a nitrogen ligand from the pyrimidine of the tetrachloridoruthenium(III) complex related by the twofold rotation axis [Na—N = 2.5224 (14) Å] and an oxygen-bound DMSO [Na—O = 2.3165 (12) Å].


Comment
Ruthenium complexes are thought to be good candidates for the next generation of metal-based anti-cancer agents following the very successful platinum complexes whose most famous example is cisplatin; platinum complexes struggle with general toxicity, drug resistance, and lack of water solubility (Kostova, 2006;Antonarakis & Emadi, 2010;Silva, 2010). For synthesis of ruthenium precursors see: Alessio et al. (1991) and Jaswal et al. (1990).
The six-coordinate, distorted octahedral sodium cation acts to bridge the ruthenium complex into an infinite one-dimensional chain (Fig. 2). On each Ru center, cis-chloride ligands coordinate to sodium with Na1-Cl2 and Na1-Cl3 distances of 2.9576 (7)Å and 2.6988 (7) Å, respectively. A centrosymmetric dimer is formed by additional sodium coordination to Cl2 i and the DMSO oxygen O1 i of the neighboring ruthenium complex, with Na1-Cl2 i distance of 2.8888 (7)Å and Na1-O1 i distance of 2.262 (1) Å. The dimer is linked into an infinite one-dimensional chain by further coordination of the sodium ion to nitrogen N2 ii of the pyrimidine lignd of the ruthenium complex related by the twofold rotation axis with a Na1-N2 ii bond distance of 2.522 (1) Å. The final coordination site of the octahedral sodium ion is occupied by a molecule of DMSO, with Na1-O2 length 2.317 (1) Å. This infinite one-dimensional chain with the sodium cation acting as a bridge is similar to the related structure [Na][RuCl 4 (pyrazine)(DMSO)] (Anderson et al., 2007), the difference being the slight twist observed in the pyrimidine complex due to the meta nitrogen donor atoms as opposed to a more linear case for the pyrazine complex with the para nitrogen donor atoms.

Experimental
The title complex was prepared by mixing a solution of [Na][RuCl 4 (DMSO) 2 ] in acetone/DMSO (10:1) with an acetone solution of pyrimidine in fivefold excess. The resulting solution was mixed for several hours and then placed at 5 °C for several days. Large block-like crystals appeared; one was taken for X-ray diffraction studies. The others were used for spectroscopic characterization. For similar spectroscopic results see Anderson et al., (2007)

Refinement
All non-hydrogen atoms were refined anisotropically. Hydrogen atoms on carbon were included in calculated positions and refined using a riding model at C-H = 0.95 or 0.98 Å and U iso (H) = 1.2 or 1.5 × U eq (C) of the aryl and methyl C-atoms, respectively. The extinction parameter (EXTI) refined to zero and was removed from the refinement. Fig. 1. A view of the title compound, with displacement ellipsoids shown at the 50% probability level. Fig. 2. A view of the one-dimensional chain with displacement ellipsoids shown at the 50% probability level. Hydrogen atoms have been removed for clarity. [Symmetry codes: (i) -x + 1, -y, -z + 1; (ii) -x + 1, y, -z + 1/2; (iii) x, -y, z + 1/2].

Experimental. A suitable crystal was mounted in a nylon loop with Paratone-N cryoprotectant oil and data was collected on a Bruker
APEX II CCD platform diffractometer. The structure was solved using direct methods and standard difference map techniques, and was refined by full-matrix least-squares procedures on F 2 with SHELXTL Version 6.14 (Sheldrick, 2008