High cytotoxicity has been established for the 8-quinolinethiolates of copper, cadmium, indium, antimony, bismuth, ruthenium, rhodium, palladium, osmium, iridium, and platinum on HT-1080 (human fibrosarcoma), MG-22A (mouse hepatoma), and B-16 (mouse melanoma) tumor cells. The greatest activity against HT-1080 was possessed by the iridium complex, and against MG-22A by the osmium complex. All the investigated metal 8-quinolinethiolates were highly toxic in relation to NIH 3T3 normal mouse embryo fibroblasts.Keywords: 8-quinolinethiolates of metals, cytotoxicity.We showed recently that 8-quinolineselenolates of metals possess high cytotoxicity on tumor cells HT-1080 (human fibrosarcoma), MG-22A (mouse hepatoma), Neuro 2A (mouse neuroblastoma), and especially on B-16 mouse melanoma [1,2]. However all these compounds, displaying high activity to tumor cells, are also toxic in relation to normal mouse embryo fibroblasta NIH 3T3 [2].On the other hand, many organic derivatives of metals containing a metal-sulfur bond also possess antitumor activity, such as copper [3], gold [4], gallium [5], germanium [6], tin [7], rhodium [8], and palladium [9]. Consequently we decided to determine the cytotoxicity of 8-quinolinethiolates of metals in order to assess the effect of the nature of the ligand on the cytotoxicity of complexes and to compare the activity and toxicity of compounds analogous in structure containing a metal-sulfur and metal-selenium bond. N S N N S S n M n+ 1a-k 2 1 a M = Cu, b M = Cd, c M = In, d M = Sb, e M = Bi, f M = Ru, g M = Rh, h M = Pd, i M = Os, j M = Ir, k M = Pt; 1 a,b,h,k n = 2, c-g, i, j n = 3For this purpose we have synthesized a series of complexes of 8-quinolinethiol with metals 1a-k (Table 1) by the interaction of sodium 8-quinolinethiolate with metal salts and have studied their cytotoxicity (Table 2) on three lines of tumor cells HT-1080, MG-22-A, and B-16. Action was also tested on normal mouse embryo fibroblasts NIH 3T3, which also served to determine the toxicity of compounds (alternative method of determining LD 50 ). The toxicity of the corresponding di(8-quinolinyl) disulfide was determined separately. __________________________________________________________________________________________

The Rh Vaska-type complexes, trans-[Rh(CO)(Cl)(YR3)] (Y=Group 15 atom; R=aryl or alkyl), analogues of the well-known Vaska's complex, trans-[Ir(CO)(Cl)(PPh3)], are well behaved model systems for various catalytic systems. They readily undergo a variety of reactions e.g., iodomethane oxidative addition, typically forming alkyl species as intermediates, e.g., [Rh(Cl)(CO)(CH3)(I)(YR3) ~], reductive elimination, substitution, insertion, etc. These Rh(I) complexes are easy to synthesize, and in conjunction with their Pd(II) and Pt(II) analogues, are potential homogeneous catalysts to also investigate structurally due to favorable thermal stability, while the CO and PR3 ligands render IR and 31 P NMR spectroscopy as powerful tools to evaluate different ligand effects. These complexes were used to quantify electronic and steric effects of different tertiary group 15 donor ligands (P, As, Sb) [1] , including PPh2Fc (ferrocenyldiphenylphosphine), and PTA (1,3,5-triaza-7-phosphaadamantane) enabling correlations between IR, 31 P NMR and X-ray crystallographic data. Selected four-, five-and six-coordinate pseudo Vaska-type complexes are presented, illustrating structural aspects and reactivity, equilibria and thermodynamics of these with regard to iodomethane oxidative addition/ ligand substitution.

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The molecular and crystal structure of palladium quinoline-8-selenolate Pd(C 9 H 6 NSe) 2 has been determined by X-ray structural analysis. The structures of the five-membered metallocycles of palladium 8-hydroxy-, 8-mercapto-, and 8-hydroselenoquinolinates of one type are compared.Keywords: 8-mercapto-, 8-hydroseleno-, and 8-hydroxyquinolinates, chelate compounds of palladium, molecular structure.A great number of the complexes of 8-mercaptoquinoline and its derivatives [1] have been synthesized and structurally examined while investigating the metal-sulfur bond in chelate compounds of transition and nontransition elements in the Laboratory of Chelate Compounds of the Institute of Inorganic Chemistry of Riga Technical University. Where possible the results obtained were compared with the structural data of the corresponding 8-hydroxyquinolinates.To clarify the character of the M-Se(S, O) bond and the overall picture of their dynamics in fivemembered isomolecular complexes of one type with ligand atoms of one group (VI), the synthesis and X-ray structural investigations have been continued on chelate compounds of 8-hydroselenoquinoline and its derivatives. Systematic structural investigations on chelate compounds the ligands of which would contain the coordinationally reactive SeH group are not known in the literature. Consequently the main problem was the coordination possibility of selenium(II) as a ligand atom and the experimental determination of the lengths of the M-Se bonds in chelate compounds. Previously we established the molecular and crystal structures of the complexes Pt(C 9 H 6 NSe) 2 , Cd(C 9 H 6 NSe) 2 [2], Zn(C 9 H 6 NSe) 2 [3,4], In(C 9 H 6 NSe) 3 [5], and Sb(C 9 H 6 NSe) 3 [6].In the present work the synthesis and the results of the X-ray structural investigation of palladium(II) quinoline-8-selenolate Pd(C 9 H 6 NSe) 2 (1) are described. Since the crystal structures of palladium 8-mercaptoquinolinate (2) [7] and palladium 8-hydroxyquinolinate (3) [8] are known, a comparison of the structure of the five-membered metallocycles of one type and consideration of the dynamics of the experimentally found Pd-Se, Pd-S, Pd-O, and Pd-N bond lengths is possible.The crystal structure of complex 1 consists of neutral centrosymmetric Pd(C 9 H 6 NSe) 2 molecules (Fig. 1). The palladium atoms are disposed at the centers of symmetry [(000)] of the unit cell. They coordinate in a bidentate manner (Se, N) with two quinoline-8-selenol ligands, the chelate angle Se(1)PdN(1) is 85.6(1)°. Surrounding the central palladium is a trans square (2Se + 2N). The Pd-Se and Pd-N bonds (Table 1) have a covalent character, since their lengths are less than the sum of the covalent radii of the corresponding atoms (r Pd + r Se = 2.537 and r Pd + r N = 2.102 Å [9]. The Se-C(8) bond length = 1.881(4) Å is close to the value of __________________________________________________________________________________________

It has been found that the nature of the substituent, its position in the quinoline ring, and the nature of the metal significantly affect the antitumor activity and toxicity of metal 8-quinolinethiolates. The most cytotoxic towards human fibrosarcoma HT-1080 and mouse hepatoma MG-22A tumor cells are the 6-methoxy-8-quinolinethiolates of rhodium, osmium, iridium, indium, antimony, and bismuth, however these are highly toxic towards normal mouse embryonic NIH 3T3 fibroblasts. The iridium 5-methyl-8-quinolinethiolate is somewhat less active to MG-22A cells but shows quite good selectivity of action because of its markedly lower toxicity.Keywords: metal 3-and 5-methyl-8-quinolinethiolates, metal 2-and 6-methoxy-8-quinolinethiolates, synthesis, toxicity, cytotoxicity.After more than 40 years, platinum complexes occupy a high profile place in the arsenal of antitumor agents [1-3]. During this time there have appeared problems connected with their use, i.e. high overall toxicity leading to unwanted side effects and resistance to platinum preparations in a series of tumors which can develop during the time of chemotherapy. Attempts have been made to overcome these observations by changing the ligands in the platinum complexes and, more recently, by exchanging the metal [4,[7][8][9][10][11].In this respect the most promising proved to be ruthenium complexes which have low overall toxicity and are selectively accumulated in the tumor cells [4,7,[12][13][14][15][16][17][18]. Two of them have carried on to clinical investigation [14,19,20]. At the same time their rhodium and osmium analogs have shown even greater cytotoxicity towards A549 lung and T47D mammary gland carcinoma cells [21].We have shown that not only ruthenium, rhodium, and osmium but also iridium complexes [22,23] with an 8-quinolinethiol [22,23] or 8-quinolineselenol [24,25] ligand show high cytotoxicity to HT-1080 human fibrosarcoma and MG-22A mouse hepatoma tumor cells. However, all of these compounds showing high activity towards tumor cells are also toxic to normal NIH 3T3 mouse embryonic fibroblasts [22]. The toxicity of the highly active rhodium and iridium 8-quinolinethiolates can be markedly decreased by the introduction into their molecules of a methyl group at the 4 position of the quinoline ring [23]. It was also found that substituents in different positions of the quinoline ring can increase the selectivity of action of di(8-quinolyl) disulfides [26]. __________________________________________________________________________________________