SYNTHESIS AND CHARACTERIZATION OF 2 NEW CLASSES OF RUTHENIUM(III)-SULFOXIDE COMPLEXES WITH NITROGEN DONOR LIGANDS (L) - NA[TRANS-RUCL4(R2SO)(L)] AND MER,CIS-RUCL3(R2SO)(R2SO)(L) - THE CRYSTAL-STRUCTURE OF NA[TRANS-RUCL4(DMSO)(NH3)].2DMSO, NA[TRANS-RUCL4(DMSO)(IM)].H2O,ME2CO (IM=IMIDAZOLE) AND MER,CIS-RUCL3(DMSO)(DMSO)(NH3)

In this paper we report the synthesis of two new classes of chloride-sulfoxide-Ru(III) derivatives containing a nitrogen ligand (L) of general formula: Na[trans-RuCl4(R2SO)(L)] and mer,cis-RUCl3(R2SO)(R2SO)(L). Their spectroscopic characterization in the solid state (IR) and in solution (NMR, UV-Vis) is also described. The cyclic voltammetry of the complexes performed in aqueous solution shows in every case a monoelectronic and rather rapid Ru(III)/Ru(II) electron transfer. The observed formal potentials are much more positive than those reported for other Ru(III) complexes. The net charge, together with the pi acidic ability of DMSO, are the factors responsible for this behaviour. The crystal structures of Na[trans-RuCl4(DMSO)(NH3)].2DMSO (5a), Na[trans-RuCl4(DMSO)(Im)].H2O,Me2CO (5b) and mer,cis-RuCl3(DMSO)(DMSO)(NH3) (6a) have been determined by three dimensional X-ray analyses. Crystal data are: a = 9.578(2), b = 12.480(2), c = 9.594(6) angstrom, alpha = 10433(3), beta = 119.04(2), gamma = 80.71(3)-degrees, triclinic, space group P1BAR, Z = 2 for 5a; a = 10.790(4), b = 11.411(4), c = 7.658(4) angstrom, alpha = 105.92(3), beta = 93.61(1), gamma = 83.50(3)-degrees, triclinic, space group P1BAR, Z = 2 for 5b; a = 10.110(3), b = 9.718(3), c = 14.101(3) angstrom, beta = 108.89(3)-degrees, monoclinic, space group P2(1)/n, Z = 4 for 6a. Least-squares refinement bawd on 4897 (5a), 4932 (5b) and 3152 (6a) independent reflections converged to R = 0.039, 0.031 and 0.022, respectively. In 5a and 5b, the DMSO ligand is S-bonded to Ru, with Ru-S bond distances (trans to N) of 2.2797(7) and 2.2956(6) angstrom, respectively, while in 6a, one DMSO, trans to N, is S-bonded (Ru-S, 2.2714(6) angstrom), and the other, trans to Cl, is 0-bonded (Ru-0, 2.070(2) angstrom). The Ru-Cl bond distance, trans to 0, is 2.3207(7) angstrom. The Ru-Cl bond distances, trans to Cl, are similar in all three compounds averaging 2.343(6) angstrom. Relevance in the synthesis of the new derivatives comes from the known antitumor properties of isostructural Ru(III) complexes with heterocyclic nitrogen ligands. The antitumor activity of some of the new compounds are currently under investigation. Their redox potentials suggest the possibility that they might undergo an easy biological reduction in vivo.