Antibacterial activity of some unsymmetrical diorganyltellurium(IV) dichlorides

Six unsymmetrical diorganyltellurium(IV) dichlorides RR'TeCl2 (where R= phenacyl-, 1-naphthacyl-, and styrylacyl- and R' = p-methoxyphenyl, p-hydroxyphenyl-, and 3-methyl-4-hydoxyphenyl-) were tested for their antibacterial activity against gram-positive (Bacillus subtilis ATCC 6633 and Staphylococcus aureus ATCC 25923) and gram-negative (Escherichia coli ATCC 25922. Pseudomonas aeruginosa ATCC 27853 and Salmonella sp.) bacteria. Antibacterial activity was measured by disk diffusion method. Inhibition zones demonstrated that all the compounds showed good activity against gram-negative strains. Phenacyl (3-methyl-4-hydroxyphenyl) tellurium(IV) dichloride and naphthacyl (3-methyl-4-hydroxyphenyl) tellurium(IV) dichloride showed significant activity against both gram-positive and gram-negative strains. Among the tested compounds, the former exhibited maximum activity against gram-positive bacteria, while the latter against all the bacteria under study and styrylacyl (p-methoxyphenyl) tellurium(IV) dichloride against all the three gram-negative bacteria.     

Cytotoxicity, mutagenicity, cellular uptake, DNA and glutathione interactions of lipophilic trans-platinum complexes tethered to 1-adamantylamine

Cytotoxicity and mutagenicity of trans,trans,trans-[PtCl₂(CH₃COO)₂(NH₃)(1-adamantylamine)] [trans-adamplatin(IV)] and its reduced analog trans-[PtCl₂(NH₃)(1-adamantylamine)] [trans-adamplatin(II)] were examined. In addition, the several factors underlying biological effects of these trans-platinum compounds using various biochemical methods were investigated. A notable feature of the growth inhibition studies was the remarkable circumvention of both acquired and intrinsic cisplatin resistance by the two lipophilic trans-compounds. Interestingly, trans-adamplatin(IV) was considerably less mutagenic than cisplatin. Consistent with the lipophilic character of trans-adamplatin complexes, their total accumulation in A2780 cells was considerably greater than that of cisplatin. The results also demonstrate that trans-adamplatin(II) exhibits DNA binding mode markedly different from that of ineffective transplatin. In addition, the reduced deactivation of trans-adamplatin(II) by glutathione seems to be an important determinant of the cytotoxic effects of the complexes tested in the present work. The factors associated with cytotoxic and mutagenic effects of trans-adamplatin complexes in tumor cell lines examined in the present work are likely to play a significant role in the overall antitumor activity of these complexes.     

Synthesis of 5,6-dihydro-4H-1,3-oxazines from neutral and cationic platinum(II) nitrile complexes. X-ray structure of trans-[Pt(CF3){ H2CH2}(PPh3)2]BF4

The 1,3-oxazine complexes cis- and trans-[PtCl₂{ C(R)OCH₂CH₂C}H₂₂] (cis: R=CH₃ (1a), CH₂CH₃ (2a), (CH3)₃C (3a), C₆H₅ (4a); trans:R =CH₃ (1b), C₆H₅ (4b)) were obtained in 51-71% yield by reaction in THF at 0 °C of the corresponding nitrile complexes cis- and trans-[PtCl2(NCR)₂] with 2 equiv. of ⁻OCH₂CH₂CH₂Cl, generated by deprotonation of 3-chloro-1-propanol with n-BuLi. The cationic nitrile complexes trans-[Pt(CF₃)(NCR)(PPh₃)₂]BF₄ (R=CH3, C₆H₅) react with 1 equiv, of ⁻ OCH2CH2CH2Cl to give a mixture of products, including the corresponding oxazine derivatives trans-[Pt(CF₃){ CH₂}(PPh₃)₂]BF₄ (5 and 6), the chloro complex _trans- [Pt(CF₃)Cl(PPh₃)₂] and free oxazine H2. For short reaction times (c. 5–15 min) the oxazine complexes 5 and 6 could be isolated in modest yield (37–49%) from the reaction mixtures and they could be separated from the corresponding chloro complex (yield 40%) by taking advantage of the higher solubility of the latter derivative in benzene. For longer reaction times (> 2 h), trans-[Pt(CF₃)Cl(PPh₃)₂] was the only isolated product. Complex 6 was crystallographically characterized and it was found to contain also crystals of trans- [PtCl{ H₂}(PPh₃)₂]BF₄, which prevented a more detailed analysis of the bond lengths and angles within the metal coordination sphere. The 1,3-oxazine ring, which shows an overall planar arrangement, is characterized by high thermal values of the carbon atoms of the methylene groups indicative of disordering in this part of the molecule in agreement with fast dynamic ring processes suggested on the basis of ¹H NMR spectra. It crystallizes in the trigonal space group P , with a=22.590(4), b=15.970(3) Å, γ=120°, V=7058(1) ų and Z=6. The structure was refined to R=0.059 for 3903 unique observed (I3σ(I)) reflections. A mechanism is proposed for the conversion of nitrile ligands to oxazines in Pt(II) complexes.     

Differential genotoxic effects of antitumor trans-[PtCl2(E-iminoether)2] and cisplatin in Escherichia coli

In the present work, we measured survival and the platinum on the genome after treatment of repair-proficient or repair-deficient Escherichia coli strains with trans-[PtCl₂(E-iminoether)₂] and compared these results with the effects of “classical” cisplatin. We found that toxicity of antitumor trans-[PtCl₂(E-iminoether)₂] in repair-deficient trains was much less than that of cisplatin. This markedly reduced toxicity was not a consequence of the reduced uptake or low levels of DNA binding in the bacteria cells but rather appeared to reflect DNA binding mode of this trans-platinum drug different from that of cisplatin.     

Synthesis,Ti(IV) intake by apotransferrin and cytotoxic properties of functionalized titanocene dichlorides

Functionalization of cyclopentadienyl (Cp) ligands and incorporation of these into a Ti(IV) center require careful design and selection of the appropriate synthetic routes to obtain the desired product in reasonably good yields. As part of our research efforts in the area of titanocene antitumor agents, we have revisited the synthesis of Cp rings with electron-withdrawing groups and their corresponding titanocene dichlorides, (Cp-R)₂TiCl₂ and (Cp-R)CpTiCl₂, where R is CO₂CH₃ and CO₂CH₂CH₃. These complexes were characterized by elemental analysis and ¹H and ¹³C NMR and IR spectroscopies. This report presents the first detailed synthetic route for (Cp-CO₂CH₂CH₃)CpTiCl₂ and provides an alternate route for synthesis of (Cp-R)₂TiCl₂ complexes. The ability of these complexes to deliver Ti(IV) to apotransferrin was investigated to elucidate how the functionalized Cp ligands affect the titanium intake by apotransferrin. The subject complexes transfer Ti(IV) to human apotransferrin, loading both N- and C-lobes. The antitumor activity of these complexes against HT-29 cancer colon cells was determined using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Carboethoxy Cp functionalization results in complexes with a toxicity comparable to that of titanocene dichloride. The carbomethoxy-functionalized complexes proved to be nonactive at the time intervals studied here, regardless of their ability to donate the titanium atom to human apotransferrin.     

Positional Isomerization of trans-3-Hexadecenoic Acid Employing 2-Amino-2-methyl-propanol as a Derivatizing Agent for Ethylenic Bond Location by Gas-Chromatography/Mass Spectrometry

The effect of derivatization with 2-amino-2-methyl-propanol on trans-3-hexadecenoic acid was investigated as part of the identification of the trans-3-hexadecenoic acid in two Nova Scotian seaweeds. After the extraction of the total fatty acids and their methylation, the monoenoic trans fraction was isolated by thin-layer chromatography on silica gels impregnated with silver nitrate. This fraction was first analyzed by gas chromatography and showed the presence of the trans-3-hexadecenoic acid; other fatty acids were not present. The isolated fraction was derivatized with 2-amino-2-methyl-propanol prior to analysis by gas chromatography/mass spectrometry. The chromatogram obtained showed the presence of a positional isomer formed during the derivatization of the trans-3-hexadecenoic acid. The mass spectrum showed a prominent [M + H]⁺ and diagnostic ions for the identification of the unknown isomer, corresponding to the 4,4-dimethyloxazoline (DMOX) derivative of a presumed 2-hexadecenoic acid. Definitive confirmation of the ethylenic bond position was obtained by oxidative ozonolysis of the DMOX derivatives of the fatty acids under investigation. Infrared spectroscopy showed that the artifact formed during the DMOX derivatization of trans-3-hexadecenoic acid was the DMOX derivative of cis-2-hexadecenoic acid.     

Tellurium tetrahalides in rubber chemistry: Some new tellurium(IV) complexes with an S2X4 (X = halogen) ligand environment

The reaction of tellurium tetrahalides with natural rubber parallels closely reactions with model compounds such as cyclohexene and 2-methyl- pent-2-ene carried out under similar conditions. In both cases an α-elimination reaction of an ‘organic halide’ with deposition of elemental tellurium is a dominant process, but some evidence for cross- linking of natural rubber is obtained. If methyl cyanide is the solvent for cyclohexene, or if a nitrile rubber is used, elimination of tellurium is inhibited.Tellurium tetrachloride enhances the rate and density of cross-link formation when added to tetramethylthiuram disulphide (TMTD) based natural rubber vulcanisates, but this effect is negated in the presence of triphenylphosphine. TeCl₄ reacts with TMTD to eliminate an atom of sulphur and to form a complex of tetramethylthiuram monosulphide (TMTM) viz. [Te(TMTM)Cl₄]. Corresponding bromo- and iodo-complexes have been prepared, the iodo- complex is a 1:1 electrolyte. ¹²⁵Te Mössbauer data for the complexes are briefly discussed.Further reactions of the complexes are described which lead to the formation of: [Te(TMTM)Cl₂(O)(pyridine)], [Te(TMTM)X₂(O)] (X=Br, I), and [Cu(TMTM)₂] [TeCl₅]₂. Organyltellurium(IV) trihalides also react with TMTD to release sulphur and give complexes of TMTM, i.e. [(p-EtO·C₆H₄)Te- X₃]₂(TMTM) (X=Cl, Br, I).     

2-Thiophenyltellurium derivatives: Alternative synthetic routes and structural characterization

Grignard reagent prepared from 2-thiophenyl bromide in THF consumes elemental tellurium readily at room temperature and provides a route to obtain bis(2-thiophenyl)ditelluride, Tpn₂Te₂ (1, Tpn = 2-C₄H₃S) in good yield. It can also thiophenylate aryltellurium(II) bromides, producing solutions of mixed aryl(heteroaryl)tellurides, which when chlorinated give crystalline aryl(heteroaryl)tellurium(IV) dichlorides, ArTpnTeCl₂ (Ar = 1-C₁₀H₇, Npl; 2,4,6-Me₃C₆H₂, Mes). Oxidative addition of α-bromo-N,N-diethylacetamide to (2-thiophenyl)tellurium(II) bromide, gave the mixed alkyl(heteroaryl)tellurium(IV) dibromide, (Et₂NCOCH₂)TpnTeBr₂. Ditelluride 1 can be detellurated by electrolytic copper to the bis(2-thiophenyl)telluride, Tpn₂Te (2). Chemical shifts, δ(¹H, ¹³C and ¹²⁵Te) for (2-thiophenyl)tellurium(IV) halides are reported. Crystal structures of Tpn₂TeBr₂ (2b), Tpn₂TeI₂ (2c) and Mes(Tpn)TeCl₂ (2e) have been determined unambiguously. In the case of 2e, steric repulsion of the mesityl ligand counters the tellurium lone pair repulsion to widen the equatorial C-Te-C angle to the extent of 108°. In the crystal lattices of 2b and 2c, the intermolecular Te?X secondary bonds give rise to an interesting tetrameric supramolecular architecture with S₂ symmetry that defies the stereochemical activity of the lone pair on the central tellurium atom.     

Elaidic and trans-vaccenic acids in plasma phospholipids as indicators of dietary intake of 18:1 trans-fatty acids

Octadecenoic (18:1) trans-fatty acid fractions from margarine, butter and plasma phospholipids (PL) were isolated by silver ion TLC, and nine positional isomers (n-11-n-3) were identified by GC-MS based on their ozonolysis products. The GC analysis of the isolated fractions gave similar peak profiles and separated seven trans-isomers (n-11-n-6 and n-3). Without a preceding isolation step, the reproducibility of the Gc method for plasma PL elaidic (18:1 n-9 trans) and trans-vaccenic acids (n-7) was 3.4 and 2.7% (R.S.D.), respectively. These trans-isomers were rapidly incorporated and cleared in plasma PL and they closely reflected both increased and decreased intake of 18:1 trans-fatty acids during moderate fat substitutions. Significant associations between high-density lipoprotein cholesterol (HDL-C) and PL elaidic and trans-vaccenic acids appeared in habitual margarine users only.     

Synthesis, crystal structures, cytotoxicity and qualitative structure-activity relationship (QSAR) of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}di-n-butyltin(IV) complexes, (n)Bu2Sn(L)2

A series of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}di-n-butyltin(IV) complexes has been synthesized and characterized by ¹H-, ¹³C-, ¹¹⁹Sn NMR, ESI-MS (electrospray ionization mass spectrometry), IR and ^119mSn Mössbauer spectroscopic techniques in combination with elemental analyses. The structures of four di-n-butyltin(IV) complexes, viz., ⁿBu₂Sn(L³)₂ (3), ⁿBu₂Sn(L⁴)₂ (4), ⁿBu₂Sn(L⁵)₂ (5) and ⁿBu₂Sn(L⁷)₂ · 0.5C₆H₆ (7) (LH = 5-[(E)-2-(aryl)-1-diazenyl)quinolin-8-ol) were determined by single crystal X-ray diffraction. In general, the complexes were found to adopt a distorted cis-octahedral arrangement around the tin atom. These complexes retain their solid-state structure in non-coordinating solvent as evidenced by ¹¹⁹Sn and ¹³C NMR spectroscopic results. The in vitro cytotoxicity of di-n-butyltin(IV) complexes (3-8) is reported against seven well characterized human tumour cell lines. The basicity of the two quinolinolato donor N and O atoms of the ligands are discussed in relation to the cytotoxicity data.     

Molecular basis of the interaction of novel tributyltin(IV) 2/4-[(E)-2-(aryl)-1-diazenyl]benzoates endowed with an improved cytotoxic profile: Synthesis, structure, biological efficacy and QSAR studies

A series of tributyltin(IV) complexes based on 2/4-[(E)-2-(aryl)-1-diazenyl]benzoate ligands was synthesized, wherein the position of the carboxylate and aryl substituents (methyl, tert-butyl and hydroxyl) varies. The complexes, Bu₃SnL^1-4H (1-4), have been structurally characterized by elemental analysis and IR, NMR (¹H, ¹³C, and ¹¹⁹Sn) and ¹¹⁹Sn Mössbauer spectroscopy. All have a tetrahedral geometry in solution and a trigonal bipyramidal geometry in the solid-state, except for Bu₃SnL⁴H (4) that was ascertained to have tetrahedral coordination by X-ray crystallography. Cytotoxicity studies were carried out on human tumor cell lines A498 (renal cancer), EVSA-T (mammary cancer), H226 (non-small-cell lung cancer), IGROV (ovarian cancer), M19 MEL (melanoma), MCF-7 (mammary cancer) and WIDR (colon cancer). Compared to cisplatin, test compounds 1-4 had remarkably good activity, despite the presence of substantial steric bulk due to Sn-Bu ligands. The quantitative structure-activity relationship (QSAR) studies for the cytotoxicity of organotin(IV) benzoates, along with some reference drug molecules, is also discussed against a panel of human tumor cell lines. Molecular structures of the tributyltin(IV) complexes (1-4) were fully optimized using the PM6 semi-empirical method and docking studies performed with key enzymes associated with the propagation of cancer, namely ribonucleotide reductase, thymidylate synthase, thymidylate phosphorylase and topoisomerase II. The theoretical results are discussed in relation to the mechanistic role of the cytotoxic active test compounds (1-4).     

An in vitro comparative assessment with a series of new triphenyltin(IV) 2-/4-[(E)-2-(aryl)-1-diazenyl]benzoates endowed with anticancer activities: structural modifications, analysis of efficacy and cytotoxicity involving human tumor cell lines

Four new triphenyltin(IV) complexes of composition Ph₃SnLH (where LH = 2-/4-[(E)-2-(aryl)-1-diazenyl]benzoate) (1-4) were synthesized and characterized by spectroscopic (¹H, ¹³C and ¹¹⁹Sn NMR, IR, ¹¹⁹Sn Mössbauer) techniques in combination with elemental analysis. The ¹¹⁹Sn NMR spectroscopic data indicate a tetrahedral coordination geometry in non-coordinating solvents. The crystal structures of three complexes, Ph₃SnL¹H (1), Ph₃SnL³H (3), Ph₃SnL⁴H (4), were determined. All display an essentially tetrahedral geometry with angles ranging from 93.50(8) to 124.5(2)°; ¹¹⁹Sn Mössbauer spectral data support this assignment. The cytotoxicity studies were performed with complexes 1-4, along with a previously reported complex (5) in vitro across a panel of human tumor cell lines viz., A498, EVSA-T, H226, IGROV, M19 MEL, MCF-7 and WIDR. The screening results were compared with the results from other related triphenyltin(IV) complexes (6-7) and tributyltin(IV) complexes (8-11) having 2-/4-[(E)-2-(aryl)-1-diazenyl]benzoates framework. In general, the complexes exhibit stronger cytotoxic activity. The results obtained for 1-3 are also comparable to those of its o-analogs i.e. 4-7, except 5, but the advantage is the former set of complexes demonstrated two folds more cytotoxic activity for the cell line MCF-7 with ID₅₀ values in the range 41-53 ng/ml. Undoubtedly, the cytotoxic results of complexes 1-3 are far superior to CDDP, 5-FU and ETO, and related tributyltin(IV) complexes 8-11. The quantitative structure-activity relationship (QSAR) studies for the cytotoxicity of triphenyltin(IV) complexes 1-7 and tributyltin(IV) complexes 8-11 is also discussed against a panel of human tumor cell lines.     

Syntheses and activity of some platinum(IV) complexes with N-methyl derivate of glycine and halogeno ligands against HeLa, K562 cell lines and human PBMC

Four platinum(IV) complexes, trans,trans-dichlorobis(N,N-dimethylglycinato)platinum(IV), trans,trans-[Pt(dmgly)₂Cl₂] (1) and trans,trans-dibromobis(N,N-dimethylglycinato)platinum (IV), trans,trans-[Pt(dmgly)₂Br₂] (2), as well as, trans,trans-dichlorobis(N-methylglycinato)platinum(IV), trans,trans-[Pt(sar)₂Cl₂] (3) and trans,trans-dibromobis(N-methylglycinato)platinum(IV), trans,trans-[Pt(sar)₂Br₂] (4) (with configuration index for all complexes OC-6-14), were synthesized and characterized by elemental analysis, infrared and ¹H NMR spectroscopy. In the aim to assess the selectivity in the antitumor action of these complexes, the antiproliferative action of these compounds was determined to human adenocarcinoma HeLa cells; to human myelogenous leukemia K562 cells and to normal immunocompetent cells; i.e., on human PBMC. The details of the crystal structure synthesized trans,trans-[Pt(sar)₂Br₂] complex were also reported here. In the crystal structure of trans,trans-[Pt(sar)₂Br₂], the Pt(IV) ion had a deformed octahedral coordination with both N-methylglycinates and bromides bonded trans to one another and with the N-Pt-Br bond angles of 84.1(4) and 95.9(4)°. The trans,trans-[Pt(sar)₂Br₂] complex molecules form 2D-layers with multiple N-H?O and C-H?O hydrogen bonds.     

Synthesis of methyl O-(3-deoxy-3-fluoro-β- -galactopyranosyl)-(1→6)-β- -galactopyranoside and methyl O-(3-deoxy-3-fluoro-β- -galactopyranosyl)-(1→6)-O-β- -galactopyranosyl-(1→6)-β- -galactopyranoside

Condensation of 2,4,6-tri-O-acetyl-3-deoxy-3-fluoro-α- -galactopyranosyl bromide (3) with methyl 2,3,4-tri-O-acetyl-β- -galactopyranoside (4) gave a fully acetylated (1→6)-β- -galactobiose fluorinated at the 3′-position which was deacetylated to give the title disaccharide. The corresponding trisaccharide was obtained by reaction of 4 with 2,3,4-tri-O-acetyl-6-O-chloroacetyl-α- -galactopyranosyl bromide (5), dechloroacetylation of the formed methyl O-(2,3,4-tri-O-acetyl-6-O-chloroacetyl-β- -galactopyranosyl)-(1→6)- 2,3,4-tri-O-acetyl-β- -galactopyranoside to give methyl O-(2,3,4-tri-O-acetyl-β- -galactopyranosyl)-(1→6)-2,3,4-tri-O-acetyl-β- -galactopyranoside (14), condensation with 3, and deacetylation. Dechloroacetylation of methyl O-(2,3,4-tri-O-acetyl-6-O-chloroacetyl-β- -galactopyranosyl)-(1→6)-O-(2,3,4-tri-O-acetyl- β- -galactopyranosyl)-(1→6)-2,3,4-tri-O-acetyl-β- -galactopyranoside, obtained by condensation of disaccharide 14 with bromide 5, was accompanied by extensive acetyl migration giving a mixture of products. These were deacetylated to give, crystalline for the first time, the methyl β-glycoside of (1→6)-β- -galactotriose in high yield. The structures of the target compounds were confirmed by 500-MHz, 2D, ¹H- and conventional ¹³C- and ¹⁹F-n.m.r. spectroscopy.     

In vivo and in vitro oxidative regulation of rat aryl sulfotransferase IV (AST IV)

Sulfotransferase catalyzed sulfation is important in the regulation of different hormones and the metabolism of hydroxyl containing xenobiotics. In the present investigation, we examined the effects of hyperoxia on aryl sulfotransferase IV in rat lungs in vivo. The enzyme activity of aryl sulfotransferase IV increased 3- to 8-fold in >95% O2 treated rat lungs. However, hyperoxic exposure did not change the mRNA and protein levels of aryl sulfotransferase IV in lungs as revealed by Western blot and RT-PCR. This suggests that oxidative regulation occurs at the level of protein modification. The increase of nonprotein soluble thiol and reduced glutathione (GSH)/oxidized glutathione (GSSG) ratios in treated lung cytosols correlated well with the aryl sulfotransferase IV activity increase. In vitro, rat liver cytosol 2-naphthol sulfation activity was activated by GSH and inactivated by GSSG. Our results suggest that Cys residue chemical modification is responsible for the in vivo and in vitro oxidative regulation. The molecular modeling structure of aryl sulfotransferase IV supports this conclusion. Our gel filtration chromatography results demonstrated that neither GSH nor GSSG treatment changed the existing aryl sulfotransferase IV dimer status in cytosol, suggesting that oxidative regulation of aryl sulfotransferase IV is not caused by dimer-monomer status change.     

Inhibition of P-glycoprotein-mediated Multidrug Resistance (MDR) by N,N-bis(cyclohexanol)amine aryl esters: further restriction of molecular flexibility maintains high potency and efficacy

Conformational modulation of the aryl portion of a set of N,N-bis(cyclohexanol)amine aryl esters (1a-d) that are potent Pgp-dependent MDR inhibitors has been performed. Toward this end the trans-3-(3,4,5-trimethoxyphenyl)acrylic acid present in set 1 was substituted with 3-(3,4,5-trimethoxyphenyl)propanoic and 3-(3,4,5-trimethoxyphenyl)propiolic moieties to give sets 2 and 3, respectively. While the introduction of 3-(3,4,5-trimethoxyphenyl)propanoic moiety resulted in a definite drop in potency and efficacy, esterification with 3-(3,4,5-trimethoxyphenyl)propiolic acid gave four isomers (3a-d) that maintain high potency and possess optimal efficacy. These results are discussed in terms of conformational flexibility of the different sets of compounds.     

The cellular distribution and oxidation state of platinum(II) and platinum(IV) antitumour complexes in cancer cells

The cellular distribution of platinum in A2780 ovarian cancer cells treated with cisplatin and platinum(IV) complexes with a range of reduction potentials has been examined using elemental analysis (synchrotron radiation-induced X-ray emission). The cellular distribution of platinum(IV) drugs after 24 h is similar to that of cisplatin, consistent with the majority of administered platinum(IV) drugs being reduced. Micro-X-ray absorption near-edge spectra of cells treated with cisplatin and platinum(IV) complexes confirmed the reduction of platinum(IV) to platinum(II). In cells treated, the most difficult to reduce complex, cis,trans,cis-[PtCl₂(OH)₂(NH₃)₂], platinum(IV) was detected in the cells along with platinum(II). The observations are in accordance with the relative ease of reduction of the platinum(IV) complexes used and support the requirement of reduction for activation of platinum(IV) complexes.Abbreviations en ethane-1,2-diamine - GM growth medium - PBS phosphate buffered saline - RPMI Roswell Park Memorial Institute - SRIXE synchrotron radiation-induced X-ray emission - XAFS X-ray absorption fine structure - XANES X-ray absorption near-edge spectroscopy     

2-(R-1H-Benzoimidazol-2-yl)-6-(1-aryliminoethyl)pyridyliron(II) dichlorides: Synthesis, characterization and the ethylene oligomerization behavior

Iron(II) dichloride complexes bearing 2-(methyl-substituted 1H-benzoimidazol-2-yl)-6-(1-aryliminoethyl)pyridines (Fe1–Fe6) or 2-(chloro-substituted 1H-benzoimidazol-2-yl)-6-(1-aryliminoethyl)pyridines (Fe7–Fe12) were synthesized and characterized by FT-IR and elemental analysis. Single crystal X-ray crystallographic analyses revealed that complexes Fe2 and Fe3 possessed a distorted square-pyramidal geometry at iron. Upon activation with either MAO or MMAO, all iron pro-catalysts showed good activities toward ethylene oligomerization with high selectivity for α-olefins and high K values. The influence of the reaction conditions and the nature of the ligands on the catalytic performance of these iron complexes were investigated.     

A new route to N(1)-5R-tetrazole complexes via azidation to nitriles coordinated to Pt(II) and Pt(IV)

New tetrazolate complexes trans-[PtCl₂(RCN₄)₂]²⁻, trans-[PtCl₄(RCN₄)₂]²⁻ with Ph₃PCH₂Ph⁺ and (CH₃)₂NH₂⁺ counterions have been obtained by azidation of nitriles coordinated to Pt(II) and Pt(IV) {trans-[PtCl₂(RCN)₂] and trans-[PtCl₄(RCN)₂] (R = Et, Ph)} and characterized. The composition and the molecular structure of the complexes obtained were established by the СHN elemental analyses, ¹Н and ¹³С NMR spectroscopy, IR spectroscopy, mass spectrometry, and X-ray diffraction. The coordination of nitriles to Pt(II) and Pt(IV) is shown significantly activate the azidation: the reaction proceeds with a higher rate and at relatively low temperature compared with the classical 1,3-dipolar addition of azides to nitriles.     

trans-Bis[(thiocyanato-S)(1-methylimidazoline-2(3H)-thione)-μ2-(1-methylimidazoline-2(3H)-thione)copper(I)]: preparation, thermal analysis and crystal structure

1-Methylimidazoline-2(3H)-thione (mimtH) and copper(I) thiocyanate in refluxing ethanolacetonitrile produce a colourless, diamagnetic complex, [Cu₂(mimtH)₄(SCN)₂], which crystallises in an orthorhombic cell (a=8.0724(3), b=15.9545(6), c=21.3357(8) Å), space GROUP=Pbca, Z=4, final R=0.0319 from 2427 observed reflections F>4σ_c(F)). In the dimeric complex the copper(I) atoms are pseudo-tetrahedrally coordinated by pairs of, respectively, asymmetrically μ₂-S bridging mimtH, terminal monodentate-S mimtH, (Cu---S=2.290(1) Å), and terminal monodentate-S thiocyanate, (Cu---S=2.332(1) Å). Each pair of ligands is trans-related to its partner across crystallographic centres of symmetry, consequently, each copper(I) atom has an identical S₄ donor set with angles at the metal ranging from 95.9(1)° to 121.8(1)°. The centro-symmetric Cu₂S₂ core is rhomboid with Cu---S=2.377(1) and 2.457(1) Å, Cu---S_br---Cu=72.6(1)° and Cu---Cu, S_br---S_br separation distances of 2.861(1) and 3.897(2) Å, respectively. Thermal decomposition of the complex in flowing air, (133–1000 °C), involves de-sulfurisation of mimtH and thiocyanate with concomitant production of copper(II) sulfide followed by oxidation to copper(II) oxide.