Abstract:
A class of anionic and neutral complexes of ruthenium (II) containing nitrogen oxide (NO) and optionally a nitrogen ligand is described; a process for their preparation is also described. The preparation process includes the use of starting complexes of ruthenium (III) which are reacted with suitable reagents so as to obtain complexes containing NO coordinated to ruthenium (II). Additional substitution reactions allow the introduction of new groups that coordinate to the ruthenium atom, among which some nitrogen ligands.

Description:
FIELD OF THE INVENTION 
     The present invention relates the field of metal complexes; the invention concerns new anionic and neutral complexes of ruthenium (II) containing nitrogen oxide (NO) and their preparation process. 
     STATE OF THE ART 
     Numerous ruthenium complexes are described in literature with regard to studies on their structural, electrochemical and photophysical properties as well as their pharmacological activity. 
     Various anionic complexes of ruthenium have been tested for their antitumor activity ((ImH)[trans-RuCl 4 Im 2 ]: B. K. Keppler et al., J. Cancer Res. Clin. Oncol., 111: 166–168, 1986, Na[trans-RuCl 4 (Me 2 SO)(L)] where L=nitrogen ligand: WO90/13553), and have been shown to be effective in slowing down the growth of primary tumours. More recent complexes of type (LH)[trans-RuCl 4 (Me 2 SO)(L)] (WO98/00431) possess strong antimetastatic activity. 
     Various dimeric complexes of ruthenium are also known. Among these, some cationic complexes characterized by the presence of nitrogen bridging ligands (for example, heterocyclic compounds, pyridine rings) have been studied for their electrochemical and photophysical properties (Creutz et al. Journal Am. Chem. Soc., 21, 1086, 1973), while some neutral and anionic complexes have been described for their antitumoral activity (PCT/EP00/03484). The synthesis and characterisation of complexes comprising nitrogen ligands and the nitrosyl ion is reported in literature (S. Bohle et al. Eur. J. Inorg. Chem., 1609, 2000). 
     The above described ruthenium complexes exert their antitumour activity by releasing one or more of their ligands and covalently binding to biological targets. Therefore, most ruthenium complexes endowed with antitumour activity are reactive and selectively labile species and are hydrolised in aqueous solution, in particular at physiological pH. 
     In the last few years many efforts have been have been made towards the development of new ruthenium complexes endowed with antitumor activity and characterised by an improved inertness. 
     SUMMARY OF THE INVENTION 
     Object of the present invention are a class of anionic and neutral complexes of ruthenium (II) containing nitrogen oxide (NO) and optionally also a nitrogen ligand. The complexes of the invention are surprisingly inert in acqueous solution at both pH 5.5. and 7.4. Notwithstanding their high inertness, the complexes of the invention are also endowed with a cytotoxicity surprisingly higher than that of ruthenium complexes of the prior art, for example those of International Patent Application WO98/00431. 
     Therefore, the complexes of the present invention are useful for the preparation of a medicament for the therapy of tumoural or hyperproliferative pathologies. 
     A further object of the present invention is a process for the preparation of the above complexes of the invention. Said process comprises the reaction of complexes of ruthenium (III) with suitable reagents so as to obtain complexes containing NO coordinated to ruthenium (II). Additional substitution reactions allow the introduction of other groups coordinated to the ruthenium atom, among which some nitrogen ligands. 
     In the presence of suitable nitrogen ligands the above process also allows to obtain dimeric complexes of ruthenium containing NO. 
     Therefore, the complexes of the present invention are useful as intermediates for the preparation of additional ruthenium complexes. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The compounds object of the present invention are anionic or neutral complexes of ruthenium (II) of formula (I):
 
[RuA a M m P p W]
 
wherein:
     A represents a halogen chosen from the group consisting of Cl −  and Br −     W represents NO +     M represents SOR 1 R 2      P represents NR 3 R 4 R 5  or LRuA a M m W   a is a whole number between 3 and 4   m is a whole number between 0 and 2   p is a whole number between 0 and 1   r can be 0,−1,−2   being a+m+p=5
 
wherein:
   R 1  and R 2  are identical or different from each other and represent C 1 – 6  alkyl, C 3 –C 7  cycloalkyl, phenyl and aryl, or R 1  and R 2  form together with the sulphur atom a 5–7 term heterocyclic ring;   R 3 , R 4  and R 5  are identical or different from each other and represent hydrogen, saturated or unsaturated C 1 –C 6  linear or branched alkyl C 3 –C 7  cycloalkyl, phenyl and aryl, or NR 3 R 4 R 5  is a saturated or unsaturated 5–7 term nitrogen heterocyclic compound, optionally containing at least one additional eteroatom chosen from O, S, N, the latter being optionally substituted with a C 1 –C 4  alkyl, aryl or benzyl residue, said nitrogen heterocyclic compound being optionally benzocondensed and/or substituted with C 1 –C 4  alkyl, C 1 –C 4  alkoxyl, C 1 –C 4  alkylthio, benzyl or aryl;   L represents a heterocyclic ligand containing at least two heteroatoms whose electron pairs are involved in the bond with the two ruthenium atoms present in the complex.   

     Preferably, in the complexes of the invention A is chloride (Cl − ). 
     In the complexes of the invention, the coordination of the molecule W=NO occurs formally as a nitrosyl ion: NO +  and means that the state of formal oxidation of ruthenium in the products is 2+; in fact the products are diamagnetic, whereas the starting compounds are paramagnetic. 
     In the complexes of the invention of formula (I) the group M=SOR 1 R 2  is preferably represented by dimethylsulphoxide (R 1 =R 2 =methyl), diethylsulphoxide (R 1 =R 2 =ethyl), tetramethylenesulphoxide (R 1  and R 2  form a 5 term ring with the sulphur atom). The bond between the sulphoxide and ruthenium always occurs through the oxygen atom (SOR 1 R 2 ) when the sulphoxide is trans to the NO + . 
     In the complexes of the invention of formula (I) the nitrogen atom present in the nitrogen ligand P=NR 3 R 4 R 5  makes the electron pair available for the formation of the coordination bond with the ruthenium atom. In particular, the R 3 , R 4 , R 5  groups can be identical or different from each other and are chosen in the group consisting of H, saturated or unsaturated C 1 –C 6  linear or branched alkyl, C 3 –C 7  cycloalkyl, phenyl or aryl. 
     When NR 3 R 4 R 5  is a 5-member nitrogen heterocyclic compound it is preferably chosen from the group consisting of imidazole, N-methylimidazole, pyrazole and oxazole; even more preferably, said nitrogen heterocyclic compound is imidazole. 
     When NR 3 R 4 R 5  is a 6-member heterocyclic compound, it is preferably chosen from the group consisting of pyridine, 3,5-lutidine and 4-methyl-pyridine. 
     When NR 3 R 4 R 5  is a 7-member heterocyclic compound, it is preferably chosen from the group consisting of azepine, diazepine and oxazepine. 
     Lastly, when said heterocyclic compound is benzocondensed, it is preferably chosen in the group consisting of indazole, isoquinoline, benzimidazole and 1,5,6-trimethyl-benzimidazole. 
     In the complexes of the invention of formula (I) the heterocyclic ligand L present in the group P=LRuA a M m W always contains two nitrogen atoms that are coordinated through their electron pairs with the two ruthenium atoms of the complex of formula (I). Such nitrogen atoms can be on the same heterocyclic ring or on two separate heterocyclic rings. In the latter case, the ligand L assumes the structure B′-X-B″, where B′ and B″ represent the two nitrogen heterocyclic compounds that are coordinated with the two ruthenium atoms, and X represents —COO—, —O—, —(CH 2 ) n —, —(CH=CH) n —, -(aryl) n -, -(heterocyclic compound) n -, —CH=CH-Phe-CH=CH—, —(C≡C) n —, where n is between 0 and 4. 
     The heteroaromatic or aromatic rings contained in the structure B′-X-B″ can be condensed or uncondensed and substituted with a group chosen from alkyl groups having from 1 to 6 carbon atoms (the methyl and ethyl groups are preferred), C 1 –C 4  alkoxy, phenyl groups, CN and NO 2.    
     Examples of uncondensed heteroaromatic rings are: pyrrole, imidazole, pyrazole, pyrazine, pyrimidine, pyridine. 
     Examples of condensed heteroaromatic rings are: quinoline, isoquinoline, carbazole. 
     Examples of condensed aromatic rings are: naphthalene, anthracene, phenanthrene. 
     Preferred examples of B′-X-B″, whose structure is shown below, are:
     4,4′-bipyridyl (B′=B″=pyridine, X=—(CH 2 ) n —, where n=0),   bis-imidazole (B′=B″=imidazole, X=—(CH 2 ) n — where n=0)   1,2-bis(4-pyridyl)ethane (B′=B″=pyridine, X=—(CH 2 ) 6 — where n=2),   1,2-bis(4-pyridyl)propane (B′=B″=pyridine, X=—(CH 2 ) n — where n=3),   trans-1,2-bis(4-pyridyl)ethylene (B′=B″pyridine, X=—(CH=CH) n — where n=1).   

     When formula (I) represents an anionic species (i.e. r=−1, −2) then a cation (Q) must be present. Said cation (W) is preferably a proton bound to a base (e.g. (Me 2 SO) 2 H + ) or is chosen from the group consisting of alkaline or alkaline-earth metals, cations of formula  + NR 3 R 4 R 5 R 6  where R 3 , R 4 , R 5 , R 6  are identical or different to each other and represent hydrogen, saturated or unsaturated C 1 –C 6  linear or branched alkyl, C 3 –C 7  cycloalkyl, phenyl and aryl, or where  + NR 3 R 4 R 5 R 6  is to a saturated or unsaturated 5–7 term nitrogen heterocyclic compound, optionally containing at least one eteroatom chosen from O, S, N, the latter being optionally substituted with a C 1 –C 4  alkyl, aryl or benzyl residue, said nitrogen heterocyclic compound being optionally benzocondensed and/or substituted with C 1 –C 4  alkyl, C 1 –C 4  alkoxyl, C 1 –C 4  alkylthio, benzyl or aryl. 
     The preferred meanings of Q are Na + , K + , NH 4   + , Net 4   +  (tetraethylammonium), Nbu +  (tetrabutylammonium), ImH +  (imidazole). 
     In the anionic complexes of formula (I) having P represented by NR 3 R 4 R 5  Q is preferably  + NR 3 R 4 R 5 R 6  with R 6 =H and R 3 , R 4 , R 5  having the same meaning as R 3 , R 4 , R 5  present in P. 
     Ruthenium complexes particularly preferred according to the present invention are salts of anionic complexes of formula (I) wherein A=Cl, M=Me 2 SO, W=NO, a=4, m=1, p=0, r=−1 and are salts of anionic complexes of formula (I) wherein A=Cl, P=imidazole, W=NO, a=4, m=0, p=1, r=−1. 
     The metal complexes may contain crystallization molecules like SOR 1 R 2 , acetone nitromethane or water. 
     The complexes of the invention have the advantage of being stable. In fact, the coordination bond between ruthenium and W=NO +  is very stable and the nitrogen oxide does not free itself easily from the complex. Furthermore, in the complexes having also an M represented by SOR 1 R 2  also said sulphoxide ligand is stable. 
     An additional object of the present invention is the process for the preparation of the ruthenium complexes of formula (I) described above. 
     The process of the invention may comprise a single step (Step 1) or two steps 
     (Step 1 and Step 2). 
     Step 1: The starting complex [Ru III A 4 M 2 ] −1  or [Ru III A 3 M 3 ], where A and M have the same meanings described for the complex of formula (I), is dissolved in suitable organic solvents or mixtures thereof (e.g. dichloromethane, chloroform, acetone, acetone and DMSO, DMSO, nitromethane, water). Gaseous NO or a suitable NO generating reagent, is added to this solution for a period of time between 15 minutes and 5 hours, preferably between 1 and 2 hours, and the reaction is allowed to occur for a period of time between 30 min and 24 hours, preferably between 1 and 4 hours, at a temperature of between 0 and 200° C., preferably between 15 and 150° C. The reaction leads to the a corresponding anionic or neutral complex containing the W group of formula [Ru II A 4 M 1 W] −1  or [Ru II A 3 M 2 W]. 
     Step 2: The complex obtained at step 1 can be subsequently modified by reaction with P in suitable organic solvents or mixtures thereof (e.g. dichloromethane, chloroform, acetone, acetone and DMSO, DMSO, nitromethane) for a period of time between 15 min and 5 hours, preferably between 1 and 4 hours and at a temperature between 0 and 150° C. After isolation and purification a complex of formula [RuA 4 P 1 W] −1  or [RuA 3 M 1 P 1 W] is obtained. The reaction also allows the preparation of the complex [RuA 3 P 2 W]. 
     The above described two-step reaction process allows to obtain symmetrical or asymmetrical anionic or neutral dimeric complexes of ruthenium (II) with NO + , for example dimers of formula: [(RuA 4 W) 2 L] −2 , [RuA 3 MW) 2 L], [(RuA 4 W)(LRuA 3 MW)] −1 . Alternatively, symmetrical dimers of the complexes of the invention can also be obtained through a two-step process comprising Step 1 followed by Step 3. 
     Step 3 consists of the reaction between the products of step 1, [Ru II A 4 M 1 W] −1  or [Ru II A 3 M 2 W] with ½ equivalent of L. 
     The gaseous nitrogen oxide (NO) used in the processes described above can be flushed into the reaction vessels directly from a cylinder containing said gas. Alternatively, nitrogen oxide can be generated by decomposition of nitrites. The oxide can thus be first produced by dripping concentrated sulphuric acid onto NaNO 2  and then bubbled through a saturated aqueous solution of NaOH before conveying it to the reaction vessel. Alternatively, as regards the in situ production of nitrogen oxide, organo-nitrosyl reagents can be used such as MeN(NO)(CONH 2 ), Et 2 NNO, Cl 3 CNO. The nitrogen oxide can be added to the starting ruthenium complex directly as the nitrosyl ion NO + , usually as NOBF 4  or NOPF 6 . Said complexes can be used as starting products for the preparation of other ruthenium complexes comprising the nitrosyl group. 
     Although they are more inert, the ruthenium complexes of the invention have a more pronounced antiproliferative and cytotoxic activity compared with that of the ruthenium complexes of the prior art such as the compounds of formula LH[trans-RuCl 4 (Me2SO)(L)] and are suitable for use in the treatment hyperproliferative or tumoral pathologies. 
     Therefore, a further object of the present invention is the use of the ruthenium complexes of the invention as active agents in the manufacture of a medicament for the treatment of tumoral and hyperproliferative pathologies, such as, for example, cancer, psoriasis and rheumatoid arthritis. 
     A further object of the present invention are pharmaceutical compositions comprising a therapeutically effective amount of at least one of the ruthenium complexes of the invention in combination with suitable pharmaceutically acceptable excipients and/or diluents. 
     The invention will be better understood with reference to the following examples that are provided for illustrative, non-limiting purposes. 
     EXPERIMENTAL PART 
     Example 1 
     Preparation of the complex [(Me 2 SO) 2 H][trans-Ru II Cl 4 (Me 2 SO—O)NO] corresponding to formula (I) with A=Cl, M=Me 2 SO, W=NO, a=4, m=1, p=0, r=−1. 
     1.2 g of [(Me 2 SO) 2 H][trans-Ru III Cl 4 (Me 2 SO—S) 2 ] (1.44 mmol) (E. Alessio et al, Inorg. Chem., 30,609,1991) are dissolved in 1.3 ml of Me 2 SO and 31 ml of acetone in a 100 ml flask. The orange solution is kept under magnetic agitation under a nitrogen oxide flow for 2 hours and afterwards is left under agitation in NO atmosphere overnight. The suspension obtained is vacuum-filtered and the purple solid recovered is washed first with cold acetone and then with ethyl ether and vacuum dried. Additional fraction of products are obtained from the mother waters. 
     Total yield: 0.80 g (73%). MW 508.28. C 6 H 19 N 1 Cl 4 O 4 S 3 Ru 1 ]. [Elementary Analysis-theoretical: % C 14.18, % H 3.77, % N 2.76, experimental: % C 14.1, % H 3.72, % N 2.92. Spectrum  1 H-NMR (ppm) D 2 O:Ru(II)—Me 2 SO—O 2.95 (s, 6H), Me 2 SO 2.71 (s, 12H). IR spectrum (KBr, cm −1 ): ν (N≡O) 1864, ν (S—O) 924, ν [(Me 2 SO) 2 H] 725, ν (Ru—O) 501. The structure was ascertained by X-ray. 
     Example 2 
     Preparation of the complex [NBu 4 ][trans-Ru II Cl 4  (Me 2 SO—O)NO], corresponding to formula (I) with A=Cl, M=Me 2 SO, W=NO, a=4, m=1, p=0, r=−1. 
     A solution of 0.278 g (1.00 mmol) of tetrabutylammonium chloride in 1.4 ml of water is added to a red solution of 0.252 g of [(Me 2 SO 2 H][trans-Ru II C 4 (Me 2 SO—O)NO] (0.496 mmol) in 2 ml of water. After the addition, a dark pink precipitate is formed which is vacuum-filtered, washed first with a little cold acetone, then with ethyl ether and vacuum dried. Yield: 0.226 g (77%). MW 593.484. [C 18 H 42 N 2 Cl 4 O 2 S 1 Ru 1 ]. 
     Elementary Analysis-theoretical: % C 36.42, % H 7.13, % N 4.72, experimental: % C 36.6, % H 7.21, % N 4.67.  1 H-NMR spectrum (ppm) CD 3 NO 2 :Ru(II)—Me 2 SO—O 2.91 (S, 6H), Bu 4 N 3.25 (m, 8H), 1.67 (m, 8H), 1.46 (m, 8H), 1.02 (t, 12H). IR spectrum (KBr, cm −1 ): ν (N≡O) 1867, (S—O) 937, ν (Ru—O) 501. 
     Example 3 
     Preparation of the complex [ImH][trans-Ru III Cl 4 (Me 2 SO) 2 ] 
     0.5 g of the complex [(Me 2 SO) 2 H][trans-Ru III Cl 4 (Me 2 SO 2 ] (1 mmol) are dissolve 23 ml of ethanol and 0.3 ml of H 2 O. 188 mg of solid ImHCl (1.8 mmol) are added to the solution under stirring. The product immediately precipitates as a red-orange coloured microcrystalline solid, which is directly vacuum-filtered, washed with cold ethanol, cold acetone and ethyl ether and vacuum dried. Yield: 0.35 g (75%). MW 468.22 [C 7 H 17 N 2 Cl 4 O 2 RuS 2 ]. 
     Elementary Analysis-theoretical: % C 17.9, % H 3.65, % N 5.98, experimental: % C 18.1, % H 3.67, % N 5.94. The UV-vis, NMR spectra confirm the presence of the anion [trans-RuCl 4 (Me 2 SO) 2 ] −  and of the cation ImH + . 
     Example 4 
     Preparation of the complex [ImH][trans-Ru II Cl 4 (Me 2 SO—O)NO], corresponding to formula (I) with A=Cl, M=Me 2 SO, W=NO, a=4, m=1, p=0, r=−1. 
     The synthesis is similar to that of [(Me 2 SO) 2 H][trans-Ru II Cl 4 (Me 2 SO—O)NO]. 0.5 g of [ImH][trans-Ru III /Cl 4 (Me 2 SO—S) 2 ] (1.07 mmol) are suspended in 10 ml of nitromethane. NO is bubbled through for 2 hours and a dark red solution is obtained. The solvent is removed and the oil obtained is recovered with acetone. The dark pink product that forms is vacuum-filtered, washed first with cold acetone, then with ethyl ether and vacuum dried. 
     Yield: 0.134 g (30%). MW 420.10 [C 5 H 11 N 3 Cl 40   2 S 1 Ru 1 ]. Elementary Analysis-theoretical: % C 14.29, % H 2.64, % N 10.0, experimental: % C 14.1, % H 2.49, % N 10.20.  1 H-NMR spectrum (ppm) D 2 O: ImH 8.59 (s, 1H), 7.45 (s, 2H); Ru(II)—Me 2 SO—O 2.77 (s, 6H), IR spectrum (KBr, cm −1 ): ν (N≡O) 1864, v (S—O) 922, (ImH) 626, ν (Ru—O) 501. 
     Example 5 
     Preparation of the complex [mer-Ru II Cl 3 (Me 2 SO—O) 2 NO], corresponding to formula (I) with A=Cl, M=Me 2 SO, W=NO, a=3, m=2, p=0, r=0. A solution of 0.30 g of [mer-Ru III Cl 3 (Me 2 SO—S) 2  (Me 2 SO—O)] (E. Alessio et al, Inorg. Chem., 1991, 30,609) in 6 ml of dichloromethane is kept under agitation and under a NO flow for approximately 2 hours. After one hour the formation of a reddish solid is observed. The product is vacuum-filtered, washed with a little dichloromethane/ethyl ether and vacuum dried. 
     Yield: 0.176 g (65.8%). MW 393.69. [C 4 H 12 N 1 Cl 3 O 3 S 2 Ru 1 ]. Elementary Analysis-theoretical: % C 12.2, % H 3.08, % N 3.56, experimental: % C 12.1, % H 2.85, % N 3.58. Spectrum  1 H-NMR (ppm) CD 3 NO 2 : Ru(II)Me 2 SO—O 2.97 (s, 6H), 2.91 (s, 6H). IR spectrum (KBr, cm −1 ): ν (N—O) 1878, ν (S—O) 928, 898, ν (Ru—O) 503, 492. The structure was ascertained by X-ray. 
     Example 6 
     Preparation of the complex [Nbu 4 ][trans-Ru II Cl 4 (Im)NO], corresponding to formula (I) with A=Cl, P=imidazole, W=NO, a=4, m=0, p=1, r=−1. 
     0.110 g of [Nbu 4 ][trans-Ru II Cl 4 (Me 2 SO—O)NO] (0.18 mmol) are dissolved in 5 ml of acetone. 0.050 g of imidazole (0.74 mmol) are added to the solution. The solution is refluxed for 3 hours. After approximately one hour the solution changes its colour from pink to red. The solution is allowed to cool and a dark red microcrystalline precipitate is formed that is vacuum-filtered, washed first with cold acetone, then with ethyl ether and vacuum dried. Yield: 0.036 g (33.6%). MW 583.43. [C 2 H 40 N 4 Cl 4 O 1 Ru 1 ]. 
     Elementary Analysis Theoretical: % C 39.71, % H 6.91, % N 9.60, experimental: % C 39.6, % H 7.06, % N 9.75. Spectrum  1 H-NMR (ppm) CD 3 NO 2 : Im 8.32 (s, 1H), 7.5 (s, 1H), 7.2 (s, 1H), Bu 4 N 3.26 (m, 8H), 1.70 (m, 8H), 1.40 (m, 8H), 0.96 (t, 12H). IR spectrum (KBr, cm −1 ): ν (N=O) 1861. 
     Example 7 
     Preparation of the complex [Im 2 H][trans-Ru II Cl 4 (Im)NO], corresponding to formula (I) with A=Cl, P=Imidazole, W=NO, a=1, m=0, p=1, r=−1. 
     0.150 g of [ImH][trans-Ru II Cl 4 (Me 2 SO—O)NO] (0.36 mol) are dissolved in 15 ml of acetone, 0.1 g of imidazole (1.5 mmol) are added. The solution is refluxed for 3 hours. After approximately 1.5 hours the solution changes its colour from an initial pink colour to red. The solution is allowed to cool and the solvent is removed and the oil obtained is recovered with approximately 2 ml of nitromethane. A red microcrystalline precipitate is formed that is vacuum-filtered, washed first with cold nitromethane, then with ethyl ether and vacuum dried. MW 478.13. [C9H13N7Cl14O1Ru1]. 
     Elementary Analysis-theoretical: % C 22.6, % H 2.74, % N 20.5, experimental: % C 22.4, % H 2.62, % N 20.1.  1 H-NMR spectrum (ppm) D2O: Im 8.39 (s, 1H), 7.56 (s, 1H), 7.23 (s, 1H), ImH 8.23 (s, 2H), 7.31 (s, 4H). IR spectrum (KBr, cm−1): ν (N≡O) 1873, (Im) 1064, 652, 619, (ImH) 609. 
     Example 8 
     Preparation of the complex [trans,cis,cis-Ru II Cl 2 (Me 2 SO—O) 2 (NO)NO 2 ]. 
     The solution of 0.20 g of [trans-Ru II Cl 2 (Me 2 SO—S) 4 ] (E. Alessio et al, Inorg. Chem., 1988, 27, 4099–4106) in 8 ml of dichloromethane is placed under agitation and under a NO flow for approximately 1 hour. The solution changes its colour from yellow to a deep red. The formation of an orange solid is observed after a few hours. The product is vacuum-filtered, washed first with a little dichloromethane, then with ethyl ether ether and vacuum dried. 
     Yield: 0.096 g (56.9%). MW 404.24. [C 4 H 12 N 2 Cl 2 O 5 S 2 Ru 1 ]. Elementary Analysis-theoretical: % C 1.88, % H 2.99, % N 6.93, experimental: % C 11.8, % H 2.69, % N 6.51.  1 H-NMR spectrum (ppm) CD 3 NO 2 : Ru(II)—Me 2 SO—O 2.98 (s, 6H), 2.81 (s, 6H). IR spectrum (KBr, cm −1 ): ν (N≡O) 1906, ν (S—O) 916, ν (Ru—O) 499, 486, ν (NO 2 ) 1328, 1314, δ (NO 2 ) 825. The structure was ascertained by X-ray. 
     The same product is obtained with a yield of 34.5% using [cis-RuCl 2 (Me 2 SO) 4 ] as the starting compound. 
     Example 9 
     The cytotoxicity of the ruthenium complexes prepared in Example 4 and 7 was tested on two significative tumor cell lines: MCF-7, a human hormone dependent mammary carcinoma cell line and TS/A, a murine adenocarcinoma cell line. 
     At day 0 4000 TS/A cells and 5000 MCF-7 cells were sown in 96-welled dishes in 200 μl of culture medium. The culture medium used was RPMI medium supplemented with 10% FCS for the TS/A line and a mixture 1:1 of DMEM and is F12 medium supplemented with 10% FCS for MCF-7. At day 1 the culture medium was removed and substituted with an identical medium containing 5% FCS only (control) or 5% FCS and the test compound (complex of example 4 or example 7) at the following concentrations: 0.1 μM, 1 μM, 3 μM, 10 μM, 30 μM, 100 μM, 300 μM, 600 μM and 1000 μM. 
     After 24, 48 and 72 hours cell viability was evaluated with a MTT test. The IC50 concentrations calculated for both cell lines are shown in the following table: 
     
       
         
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 TSA 
                 MCF-7 
               
             
          
           
               
                   
                 24 hours 
                 48 hours 
                 72 hours 
                 24 hours 
                 48 hours 
                 72 hours 
               
               
                   
                   
               
             
          
           
               
                 Complex of Ex. 4 
                 155 μM 
                 20 μM 
                 17 μM 
                 764 μM 
                 118 μM 
                 26 μM 
               
               
                 Complex of Ex. 7 
                 141 μM 
                 39 μM 
                 33 μM 
                 532 μM 
                 143 μM 
                 18 μM 
               
               
                   
               
             
          
         
       
     
     The results obtained show that both the ruthenium complexes tested exert a cytotoxic and antiproliferative action. Although murine cells are more sensitive towards the cytotoxic and antiproliferative activity of the compounds tested for short contact times, no difference between human and murine cells is observed for prolonged contact times. 
     The cytotoxic activity of the Ruthenium complexes tested is significantly higher compared with that of similar compounds of the prior art, such as LH[trans-RUCl 4 (Me 2 SO)(L)].