- Novel dinuclear platinum(II) Complexes containing mixed nitrogen-sulfur donor ligands
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A series of novel dinuclear platinum(II) complexes were synthesized containing a mixed nitrogen-sulfur donor bidentate chelate system in which the two platinum centers are connected by an aliphatic chain of variable length. The bidentate chelating ligands were selected to stabilize the complex toward decomposition. The pKa values and reactivity of the four synthesized complexes, namely, [Pt2(S1,S4-bis(2- pyridylmethyl)-1,4-butanedithioether)(OH2)4] 4+(4NSpy), [Pt2(S1,S6-bis(2- pyridylmethyl)-1,6-hexanedithioether)(OH2)4]4+ (6NSpy), [Pt1(S1,S8-bis(2-pyridylmethyl)-1,8- octanedithioether)(OH2)4]4+ (8NSpy), and [Pt2(S 1,S 10-bis(2-pyridylmethyl)-1,10- decanedithioether)-(OH2)4]4+ (10NSpy), were investigated. This system is of special interest because only little is known about the substitution behavior of dinuclear platinum complexes that contain a bidentate chelate that forms part of the aliphatic bridging ligand. Moreover, the ligands as well as the dinuclear complexes were examined in terms of their cytotoxic activity, and the 10NSpy complex was found to be active. Spectrophotometric acid-base titrations were performed to determine the pK a values of all the coordinated water molecules. The substitution of coordinated water by thiourea was studied under pseudo-first-order conditions as a function of nucleophile concentration, temperature, and pressure, using stopped-flow techniques and UV-vis spectroscopy. The results for the dinuclear complexes were compared to those for the corresponding mononuclear reference complex [Pt(methylthiomethylpyridine)(OH2)2]2+ (Pt(mtp)), by which the effect of the increasing aliphatic chain length of the bridged complexes could be investigated. The results indicate that there is a clear interaction between the two platinum centers, which becomes weaker as the chain length between the metal centers increases. Furthermore, differences and similarities of the N,S-system were compared to the corresponding dinuclear N,N-system studied previously in our group. In addition, quantum chemical calculations were performed to support the interpretation and discussion of the experimental data.
- Hochreuther, Stephanie,Puchta, Ralph,Van Eldik, Rudi
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- Process for preparation of dithiols
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The invention relates to the synthesis of dithiols and more particularly that of α,ω-dithiols having 5 to 20 carbon atoms. The process according to the invention comprises reacting a di-(tertiary-alkylthio)alkane with hydrogen sulphide in the presence of a solid acid catalyst. The alkane dithiol is obtained selectively and a tertiary-alkyl mercaptan is obtained as by-product. It is possible to reuse the latter in a cyclical process to produce the original di-(tertiary-alkylthio)alkane.
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- Pesticidal compositions containing phosphoric esters and divalent sulphur compounds
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Pesticidal composition comprising: a pesticidal, phosphoric ester the molecule of which has at least one alkyl group of 1 to 3 carbon atoms, 0.05 to 10% of an agent stabilizing the said ester against decomposition by protonisation, together with adjuvants characterized in that the stabilizing agent comprises at least one sulphur compound containing per molecule at least one divalent sulphur atom of which one valence is bonded to an atom chosen from sulphur, carbon, nitrogen, hydrogen, and metals capable of giving a salt, the other valence being bonded to an atom chosen from hydrogen, the carbon atom already noted, a second carbon atom, the nitrogen atom already noted, a second nitrogen atom, the metal atom already noted in the case of a metal of valence greater than one, a second atom of metal and oxygen when the first valence is not attached to an atom of hydrogen, the proportion of sulphur calculated with reference to the weight of the sulphur compound being between 5 and 99%. Process for stabilizing a phosphoric ester of which the molecule possesses at least one alkyl group containing 1 to 3 carbon atoms characterized in that there is added to the phosphoric ester or to a mixture which contains it, 0.05 to 10% calculated on the weight of the phosphoric acid ester of an agent capable of stabilizing the said phosphoric ester against protonisation and comprising at least one sulphur compound such as that defined thereupon.
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