the compounds object of the present invention are anionic or neutral complexes of ruthenium ( ii ) of formula ( i ): 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 r 1 and r 2 are identical or different from each other and represent c 1 - c 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 heterocydic compound being optionally benzocondensed and / or substituted with c 1 - c 4 alkyl , c 1 - c 4 alcoxyl , 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 peferred ), c 1 - c 4 alkoxy , phenyl groups , cn and no 2 . examples of uncondensed heteroaromatic rings are : pyrrole , imidazole , pyrazole , pyrazine , pyriridine , pyridine . 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 ) n - 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 ( q ) 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 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 - rucl4 ( 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 . 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 ( ne ≡ o ) 1864 , ν ( s — o ) 924 , ν [( me 2 so ) 2 h ] 725 , ν ( ru — o ) 501 . the structure was ascertained by x - ray . 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 cl 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 . preparation of the complex [ imh ][ trans - ru iii cl 4 ( me 2 so ) 2 ] 0 . 5 g of the complex [( me 2 so ) 2h ][ trans - ru iii cl 4 ( me 2 so 2 ]( 1 mmol ) are dissolved in 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 + . 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 nitroniethane . 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 4 o 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 , ν ( s — o ) 922 , ( imh ) 626 , ν ( ru — o ) 501 . 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 - 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 ( ne ≡ o ) 1878 , ν ( s — o ) 928 , 898 , ν ( ru — o ) 503 , 492 . the structure was ascertained by x - ray . 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 . 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 = 4 , m = 0 , p = 1 , r =− 1 . 0 . 150 g of [ imh ][ trans - ru ii cl 4 ( me 2 so — o ) no ] ( 0 . 36 mmol ) 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 . 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 . 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 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 mtu test . the ic50 concentrations calculated for both cell lines are shown in the following table : 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 antiprolferative 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 )].