Showing papers in "Applied Organometallic Chemistry in 1993"

Coordination and organometallic chemistry of cyclophosphazenes and polyphosphazenes

Abstract: This review describes the chemistry of cyclophosphazene and polyphosphazene ligand systems and their transition and organometallic complexes. The structures of the ligands and the complexes are discussed.

Antitumor effects of binuclear ferrocene derivatives

Abstract: On the basis of an earlier model of chemical carcinogenesis, the antitumor activity of the mono-, bi- and poly-nuclear ferrocene derivatives ferricenium tri-iodide (1), ferricenium tetrachloroferrate (2), 1, 1′-diethylferricenium triiodide: (3), N-(ferrocenylmethyl)hexamethylenetetramine tetrafluoroborate (4), bis(ferrocenylmethyl)benzotriazolium tetrafluoroborate (5), bis(ferrocenyl-α-ethyl)benzotriazolium tetrafluoroborate (6) and bis(ferrocenylmethyl)-2-methylbenzimidazolium tetrafluoroborate (7), and the oligomer (—Fc—CH2—Fc+˙—CH2—)7–8− (PF6)7–8 (8) was studied in vivo (FcC10H8Fe). The tumor models studied included MCH-11 (mouse sarcoma induced by methylcholantrene), P-815 (mouse mastocytoma of DBA/2 origin) and virus-induced Raucher leukemia (RLV). The cytotoxic effects of these preparations were examined against in vitro cultured normal murine cells (line L-929). The binuclear ferrocene derivatives 5, 6 and 7 inhibited the development of experimental tumors in mice. Ferricenium tri-iodide (1) was effective in Rauscher leukemia. Kinetic dependencies for most complexes had a two-phase character: the region of inhibition of tumorogenesis was followed by a region in which the complexes accelerated the development of this process. The link between the structure of compounds 1–8 and their antitumor effects is discussed.

In vitro antitumour activity of two isomeric cyclopalladiated compounds derived from benzoylbenzylidenimines

Abstract: The DNA thermal stabilizing effect and antitumour properties of two diastereoisomeric cyclopalladiated compounds, Pd2 [4-CH3O–C6H4NC(COC6H5)C6H4]2(μ-OAc)2 (I and II), derived from benzoylbenzylideneimines have been studied. The atropisomers containing two acetate-bridged PdL2 units have a folded structure in boat form. The results show that both complexes interact with the DNA double helix but that compound II stabilizes the DNA more than compound I. It was also observed that the in vitro antiproliferative activity of compound II against colon (CX-1) and lung (LX-1) human tumour cells is higher than that of compound I. It is probable that the higher reactivity of compound II relative to compound I is due to the specific orientation of the benzoyl group with respect to the COCN chiral bond.

A study of the partitioning and sorptive behaviour of butyltins in the aquatic environment

Abstract: This study was designed to investigate the partitioning and sorptive behaviour of tributyltin(TBT), and its degradation products dibutylitin (DBT) and monobutyltin (MBT), in the aquatic environment. Factorial experiments were undertaken to determine the importance of pH and particulate matter concentration in the sorption of butyltin compounds to solid phases. Results indicate that in freshwaters MBT, and to a lesser extent TBT, will be partitioned towards the particulate phase, whereas DBT exhibits a 50:50 partitioning between particulate and solution phases. In estuarine waters, whilst MBT will almost exclusively sorb on to particulates, TBT will be predominantly in the solid-phase fractions but 10–30% may remain in solution. DBT, in contrast, is solubilized in estuarine waters. A more detailed investigation of TBT sorption and particulate matter concentration was undertaken using adsorption isotherms on different sediment types. The results from batch isotherm tests plotted according to the Freundlich adsorption model revealed that TBT adsorption varied with sediment type, increasing in the order sandy-silt < silty-sand < silty-clay. TBT sorption was found to be reversible, indicating that contaminated sediments may release TBT to overlying waters following sediment distrubance. Interstitial water partitioning studies indicate that TBT predominates in the particulate phase with partition coefficients for TBT higher than for DBT and MBT. The TBT partition coefficient in interstitial waters appears to be related to total organic carbon loadings.

The analysis of organic mercury compounds using liquid chromatography with on-line atomic fluorescence spectrometric detection

Abstract: A new method for the analysis of organic mercury compounds is reported. The organomercurials are separated by high-performance liquid chromatography (HPLC). The compounds are converted to mercury(0) in a continuous-flow system by means of an oxidizing and a subsequent reducing solution. The elemental mercury generated is swept into the cell of an atomic fluorescence spectrometer (AFS) by a stream of argon. The compositions of the oxidizing solution, which contains peroxodisulphate and copper(II) in dilute sulphuric acid, and the reducing solution, which contains alkaline tin(II) chloride, were optimized, as were the gas–liquid separator (GLS), the condensing system and the geometry of the reaction coils. The method is applied to extracts of certified reference material (CRM) and to river sediments. High concentrations of methylmercury were found in the sediment samples. At one location, the presence of ethylmercury is derived from the sample chromatogram.

Diorganotin 2‐fluorocinnamates and 4‐fluorophenylacetates: Synthesis, characterization and in vitro antitumour activity

Abstract: The synthesis and characterization by spectroscopy of several new di-n-butyltin and diethyltin 2-fluorocinnamates and 4-fluorophenylacetates are described. In vitro tests on two human tumour cell lines, MCF-7, a mammary tumour, and WiDr, a colon carcinoma, showed that two of these compounds are more active than cisplatin. Other in vitro tests performed by the NCI, USA on a panel of human tumour cell line show that one of them, bis[di-n-butyl(2-fluorophenylacetato)tin] oxide, is characterized by statistically significant D, DTGI and D sensitivities, but non-significant DH and MGDH selectivities, whereas the analogous 2-fluorocinnamate shows no such significant values.

Confusion between dimethyl selenenyl sulfide and dimethyl selenone released by bacteria

Abstract: Dimethyl selenone [(CH3)2SeO2] has been reported in the literature as a metabolite released by bacteria in contact with selenium metal or selenium salts. In this study, mass spectral, chromatographic, and boiling-point data are presented that show that dimethyl selenone has been confused with dimethyl selenenyl sulfide (CH3SeSCH3). In addition, the headspaces above monocultures of selenium-resistant bacteria were examined using gas chromatography followed by fluorine-induced chemiluminescence detection. A number of alkyl sulfur and selenium species were detected, along with dimethyl selenenyl sulfide. A pathway from oxidized selenium salts to reduced methylated selenides and dimethyl selenenyl sulfide is also presented.

Identification and quantification of inorganic and organic selenium compounds with highperformance liquid chromatography

Abstract: Selenium appears in the natural selenium cycle in the form of several organic and inorganic compounds. The biologically beneficial and deterimental effects of ‘selenium’ must be ascribed to particular selenium compounds. The identification and quantification of selenium compounds in biological and environmental samples is required for an understanding of the role of selenium. The high-performance liquid-chromatographic (HPLC) methods for the separation, identification and quantification of selenite, selenate, hydrogen selenide, methaneselenol, bis(organothio) selenides, trimethylselenonium salts, selenonamino-acids, selenium derivatives of carbohydrates, selenoproteins, selenonucleosides and other miscellaneous selenium compounds are summarized (193 references) and pertinent detection modes discussed. Advantages and disadvantages of the methods are pointed out. The literature is covered since 1974, the year of the first publication in this field.

Di-n-butyltin and diethyltin monofluorobenzoates: synthesis, spectroscopic characterization and in vitro antitumor activity

Abstract: The di-n-butyltin(IV) and diethyltin(IV) fluorobenzoates [FC6H4COO]2SnR2 and (FC6H4COOR2Sn)2O have been synthesized and characterized spectroscopically. Their in vitro antitumor activity against two human tumor cell lines, MCF-7, a mammary tumor, and WiDr, a colon carcinoma, as well as against the NCI cell panel, is satisfactory.

Accumulation and toxic effect of organometallic compounds on algae

Abstract: This paper reports toxic effects and bioaccumulation factors of organometallic compounds, mainly organotin species, on algae We selected two species of microalgae as test algae: one was Scenedesmus obliquus as a representative of fresh-water algae, the other Dunaliella salina and Dunaliella viridis, to represent commonly mixed algae which exist abundantly in Tianjin Harbor, People's Republic of China For comparison, Chlorella vulgaris was also used in this study The toxic effect of ten organometallic compounds on the freshwater alga, S obliquus, was investigated The ten compounds were (as chlorides) tributyltin (TBT); triphenyltin (TPT); trimethyltin (TMT); dibutyltin (DBT); diphenyltin (DPT); dimethyltin (DMT); trimethyl-lead acetate (TML); dimethyl-arsine (DMA) and two new mixed-alkyltin pesticides, dicyclohexylmethylitin acetate (Cy2MTA) and dicyclohexylmethyltin isobutyrate (Cy2MTB) The order of toxicity of these compounds in fresh-water algae, S obliquus, was TBT>TPT>DBT> Cy2MTA=TML> Cy2MTB>DPT>TMT>DMA>DMT, according to 96 h EC50 values attained The ten toxicants were divided into three groups according to the sequence of their toxicities; (a) TBT, TPT; (b) DBT, Cy2MTA, TML, Cy2MTB; (c) DPT, TMT, DMA, DMT In each group the EC50 values of each compound were quite similar The difference of EC50 values between two vicinal groups was approximately one order of magnitude The bioconcentration factor (BCF) of TBT and TPT compared with water in the freshwater alga S obliquus was >332 × 105 and 114 × 105, respectively The BCF of the marine mixed algae was >348 × 105 The marine microalga, Chlorella vulgaris, was adaptable to TBT at lower concentration TBT at high concentration only inhibited the growth of S obliquus, but it could cause chlorosis anddisintegration of D salina and D viridis Resistance to toxicity of algae against TBT appears in order as follows: C vulgaris>S obliquus>D salina and D viridis TBT was metabolized by algae to a less toxic product, DBT The existence of algal cells accelerated the concentration reduction of TBT The toxic mechanism of TBT was also studied

Tetraethylammonium (diorgano)halogeno-(2, 6-pyridinedicarboxylato)stannates: Synthesis, characterization and in vitro antitumour activity

Abstract: The synthesis and characterization of tetraethylammonium (diorgano)halogeno(2, 6‐pyridinedicarboxylato)stannates are described. The solution structures of these complexes in CDCl3 and DMSO are discussed on the basis of 119Sn and 19F NMR data. Their in vitro antitumour activities against two human tumour cell lines, MCF‐7 and WiDr, are presented. Copyright © 1993 John Wiley & Sons, Ltd.

Arsenic metabolism in a freshwater food chain: Blue–green alga (Nostoc sp.)→ shrimp (Neocaridina denticulata)→ carp (Cyprinus carpio)

Abstract: Bioaccumulation and biomethylation of inorganic arsenic were investigated in a three-step fresh-water food chain consisting of an autotroph (blue- green alga: Nostoc sp.), a herbivore (shrimp: Neocaridina denticulata) and a carnivore (carp: Cyprinus carpio). The autotroph, herbivore and carnivore survived in arsenic-containing water below 1000, 2 and 60 mg As(V) dm−3, respectively. Bioaccumulation of arsenate by Nostoc sp. was decreased with an increase in the nitrogen concentration of the medium. Arsenic(V) was accumulated from the water phase and part-methylated by the carp, as well as by the algae and shrimp. Arsenic was mostly accumulated in the gut of the carp. The predominant arsenical in the guts was the monomethylarsenic species. Arsenic accumulation via food in the above three-step food chain decreased by one order of magnitude and the relative concentration of methylated arsenic to the total arsenic accumulated increased successively with an elevation in the trophic level. When arsenicals were transferred via the food chain, no monomethylarsenic, or only a trace amount, was detected in the three organisms. Dimethylarsenic in the alga, both dimethyl- and trimethyl-arsenic in shrimp, and trimethyl-arsenic in carp, were the predominant methylated arsenic species, respectively.

Contributions to the synthesis of some ferrocene‐containing antibiotics

Abstract: This Review discusses the synthesis and characterization by our Group of new antibiotics belonging to the class of penicillins, cephalosporins and rifamycins with ferrocenyl and 1, 1′-ferrocenilene residues in the molecule. As reactants for 6-aminopenicillanic acid (6-APA) and 7-aminocephalosporanic acid (7-ACA) the following were used: 1, 1-bis(chlorocarbonyl)ferrocene, ferrocenyl sulfochloride, 1, 1′-ferrocenylenedisulfochloride and thioglycolic acids S-modified with ferrocene. In the synthesis of rifamycins, the hydrazides of the thioglycolic acids, S-modified with ferrocene, were employed as nucleophilic agents. The synthesized intermediates were characterized by elemental analysis, TLC, IR, UV and 1H NMR spectra. The characterization of new antibiotics was made by TLC, IR and UV spectral analysis. Biological activity was tested on Gram-negative and Gram-positive bacteria. Good activity is reported towards Gram-positive bacteria in the case of derivatives containing residues of thioglycolic acid S-modified with ferrocene, the antibacterial activity being similar to that of amoxicillin, carbenicillin and cephalothin. All compounds are inactive towards Gram-negative bacteria.

Effects of tributyltin(IV) chloride exposure on early embryonic stages of Ciona intestinalis: In vivo and ultrastructural investigations

Abstract: The effects of tributyltin(IV) chloride (TBT chloride) solutions on ascidian embryos of Ciona intestinalis have been tested at different stages of development. It has been observed, in vivo, that TBT chooride inhibited cleavage of fertilized eggs and of embryo blastomeres giving rise to cellular masses that are not delimited by plasma membrane. Electron-dense precipitates of TBT chloride, probably as inorganic tin, have been observed by transmission electron microscopy in the egg cytoplasm of cellular masses. The same type of precipitate was present also inside the mitochondria, whose structure appeared to be highly modified. These ultrastructure aspects are indicative of a degenerative process of the embroys after incubation in TBT chloride.

Matrix effects in the determination of butyltin compounds in environmental samples by GC AA after hydride generation

Abstract: Experiments for the determination of mono‐, di and tri‐butyltin (MBT, DBT and TBT) by hydride generation/gas chromatography/atomic absorption spectrometry in various matrices (sediment, suspended matter, mussel, algae and water) have revealed that poor butyltin recoveries are obtained in sediments displaying high sulphur and hydrocarbon contents; very poor recoveries were also observed for TBT in sediments with high chlorophyll pigment contents as well as in algal samples. It was however not clear whether the hydride generatin was inhibited by these infering compounds, as was previously assumed in the case of hydrocarbons, or whether interferences affected the atomization rate. Further studies were performed to solve this problem in order to validate this method in the case of analyses of, for example, oil‐contaminated sediment and algae. This paper presents the results obtained. It is concluded here that the poor recoveries were due to an inhibition of hydride generation rather than to interference at the atomization stage. Copyright © 1993 John Wiley & Sons, Ltd.

Low‐temperature isospecific polymerization of propylene catalyzed by alkylzirconocene‐type ‘cations’

Abstract: The rac-ethylenebis(indenyl)methylzirconium ‘cation’ (1), generated from rac-Et(Ind)2ZrMe2 and Ph3CB(C6F5)4, has recently been shown to be exceedingly active and stereoselective in propylene polymerization. The ethyl analog (2) can be produced by an alternate, efficient route involving a reaction between rac-Et(Ind)2ZrCl2 and AlEt3 (TEA), followed by addition of Ph3CB(C6F5)4. The use of excess AlEt3 serves both to alkylate the zirconium complex as well as to scavenge the system. The propylene polymerization activity of the ‘cation’ 2 is about 7000 times greater than the activity of rac-Et(Ind)2ZrCl2/methylaluminoxane (MAO) at Tp=−20°C. The related catalyst system rac-Me2Si(Ind)2ZrCl2/TEA/Ph3CB(C6F5)4 (3) was found to produce 98.3% i-PP with Tm 156.3°C and an activity of 1.8 × 109 g PP {(mol Zr) [C3H6]h}−1.

Synthesis of 2‐substituted pyridines catalyzed by cobalt(I) complexes and promoted by light

Abstract: A series of pyridines substituted in the 2-position were synthesized by cobalt(I)-catalyzed cotrimerization of alkynes and nitriles. The reactions are usually enhanced by light. The reaction conditions are very mild. Activity and selectivity are satisfactory with respect to formation of pyridines, but depend on the type of nitrile.

Dimerization of aldehydes to carboxylic esters catalyzed by K2[Fe(CO)4]–crown ether system

Abstract: K2[Fe(CO)4] (1) with a crown ether was found to be an efficient catalyst for the dimerization of aldehydes to carboxylic esters. Several aromatic aldehydes including furfural gave the corresponding esters in good yields. This reaction also proceeded intramolecularly to give phthalide from phthalaldehyde. However, aliphatic aldehydes gave aldol-condensation products instead of the corresponding esters. In the reactions of p-substituted benzaldehydes with 1, the reactivity decreased with increase of the electron-releasing ability of the substituents. On the basis of these results, the reaction mechanism including the nucleophilic attack of tetracarbonylferrate dianion to the carbonyl carbon is discussed.

Speciation of selenoamino acids by on‐line HPLC ETAA spectrometry

Abstract: An analytical method was developed to determine selenoamino acids in the presence of other compounds. Separation has been achieved by High Performance Liquid Chromatography (HPLC) using electrothermal atomic absorption (ETAA) spectrometry as a very sensitive and element-specific detector. On-line HPLC ETAAS speciation of selenocystine and selenomethionine has been studied, using a laboratory made interface. Analytical characterization of the method has been realized with standard solutions. Using a 100μl sample loop, the detection limits were calculated as 8 μgl−1 for selenomethionine and 10 μgl−1 for selenocystine with repeatability and reproducibility of 4% and 7% respectively. The method has been applied to the determination of selenoamino acids in an extract of white clover (CRM402) certified for total selenium.

Alkylation of ionic mercury to methylmercury and dimethylmercury by methylcobalamin: simultaneous determination by purge-and-trap GC in line with FTIR

Abstract: A new approach was used to determine the reaction products of methylcobalamin and ionic mercury: purge-and-trap gas chromatography in line with Fourier transform infrared spectroscopy (PT GCIFTIR). This technique simultaneously and specifically determines the spectrum of dimethylmercury (DMeHg) and methylmercury produced by the reaction. No interference from other known organic mercury species could be detected. The method is different from others because it does not require solvent extraction of the organomercurials from aqueous solution, but relies on immediate volatilization from the reaction vessel by addition of 100 pl of 10 m~ NaBH,,. The sample was purged with nitrogen for 10 min. The volatile species of mercury were trapped in a column at -120 "C, injected into the gas chromatograph and detected by FTIR. The efficiency of DMeHg and MeHg formation depended on different parameters: pH, temperature, reaction time, and the methylcobalamin/ionic mercury ratio. The initial reaction product was MeHg which was further transformed to DMeHg. The first methylation rate was two times faster than the second. MeHg formed first, reaching a maximum at higher temperatures (28 "C and 37 "C) and later decreasing as DMeHg formed. At lower temperatures (2OOC) the rate of MeHg formation was slower, being similar to the formation rate of DMeHg. Different species of inorganic mercury such as

Seasonality in estuarine sources of methylated arsenic

Abstract: The effect of seasonal temperature change on the release of methylated arsenic from macroalgae, phytoplankton and sediment porewaters has been investigated by a series of controlled laboratory experiments. The appearance of dissolved arsenic species in the overlying waters was monitored using a coupled hydride generation/GC AA analytical technique. The liberation of dissolved arsenic species by the macroalgae Ascophyllum nodosum was examined under estuarine conditions at 5 °C and 15 °C. At the lower temperature the release rates were 0.2 μg kg−1 h−1 (wet weight of material) for monomethylarsenic (MMA) and 0.5 μg kg−1 h−1 for dimethylarsenic (DMA), whereas at 15 °C the rates were 0.4 μg kg−1 h−1 and 3.2 μg kg−1h−1, respectively. Incubation experiments were also carried out at 15 °C using the diatom Skeletonema costatum. During the log growth phase, when chlorophyll a concentrations were in the range 1-5 μg dm−3, the rate of appearance of DMA in the water was ∼3 ng dm−3 h−1. Sediment samples from the freshwater and seawater end-members of the Tamar Estuary, UK, were incubated under natural conditions at 5 °C and 15 °C. The freshwater sediments released DMA in preference to MMA; the concentrations of both species increased exponentially and reached a steady state in the overlying water after 250 h. Considerably more DMA was produced at 15 °C than at 5 °C, whilst the amount of MMA produced appeared to be insensitive to the temperature increase. In contrast, the seawater sediments always produced more MMA than DMA and the increase in temperature had little effect on the production of either MMA or DMA. The results of the laboratory experiments were compared with field observations in temperate estuaries, including the Tamar Estuary. The implications of changes of water temperature on the fate of arsenic in estuaries is discussed and modifications to the estuarine arsenic cycle are proposed.

Organometallic complexes in ascidian embryonic development: II. Effects on different stages and larvae

Abstract: The effects of the organometallic compounds Bu2Sn-D-(−;)sorbitol, Bu2Sn-D-(+)glucose, Bu2Sn-D-(−)fructose and Bu2Sn-D-(+)glyceraldehyde were tested in vivo on different stages of Ascidian development, larval movement and metamorphosis. Organotin(IV) complexes are organometallic compounds widely used as industrial biocides, antifouling agents and agricultural fungicides and are toxic to a range of organisms. Two-cell stage embryos, if incubated for one hour in the organotin (IV) solutions, stopped the cleavage, which was restored when they were transferred into normal sea water. The gastrula stage was seriously affected in 10−4mol dm−3 solutions of the above-mentioned complexes: 85% of the embryos were anomalous neurulae with open neural folds, 5% were twisted larvae. The gastrulae, when incubated for 1 h in 10−5mol dm−3 solutions, developed twisted larvae in ovular envelopes and immobile larvae with twisted tails. Larvae treated with 10−4mol dm−3 and 10−5 mol dm−3 Bu2Sn-D-(−)sorbitol, Bu2Sn-D-(+)glucose and Bu2Sn-D-(+)glyceraldehyde solutions stopped swimming, did not metamorphose and afterwards underwent cytolysis. An initial hyperactivity of circular movements, followed by immobility, was observed in the larvae incubated in Bu2Sn-D-(−;)fructose.

Antimicorbial effects of newly synthesized organotin(IV) and organolead(IV) derivatives

Abstract: Triorganotin(IV) and triorganolead(IV) derivatives of the types Me3Sn(SCZ) and Ph3Pb(SCZ) (where SCZ− is the anion of a semicarbanzone ligand) have been synthesized by substitution reactions of trimethyltin chloride and triphenyl-lead chloride with semicarbazones derived from heterocyclic ketones. The resulting complexes have been characterized by elemental analyses, molecualr weight determinations and conductivity measurements. The mode of bonding has been established on the basis of infrared and 1H, 13C and 119Sn NMR spectroscopic studies. Some respresentative complexes have also been evaluated for their antimicrobial effects on different species of pathogenic fungi and bacteria; the results of these investigations have been reported in the present paper.

Improvements in methylmercury determination prior to the certification of two tuna fish materials

Abstract: An account is given of a systematic, collaborative investigation to detect problems and sources of error in the determination of methylmercury (MeHg) in biological samples. The work was done by a group of analytical laboratories under the auspices of the Community Bureau of References (BCR) of the Commission of the European Communities (EC). The paper presents the organization of three intercomparisons on organic mercury in solution and solid matrices, and the results obtained by the participants. The different analytical steps of the methods used (extraction, clean-up, separation, final detection) are compared and assessed.

Transformations of mercury species in the presence of Elbe river bacteria

Abstract: The influence of Elbe river bacteria isolated from suspended particulate matter (SPM) on dynamic species transformation of mercury was investigated. Experiments were carried out in the presence of bacteria (batch cultures) and in sterile tapwater as a control. For the methylation of inorganic mercury ions by bacteria several cofactors are under discussion. In this work, methylcobalamin, methyl iodide and S-adenosylmethionine were tested as biogenic methyl donors and trimethyl-lead chloride, trimethyltin chloride and dimethylarsenic acid as abiotic methyl donors. Transmethylation reactions as examples of abiotic methyl transfers have higher effectiveness in the formation of methylmercury (CH3Hg+) than methylation with biogenic compounds. This result was observed in batch cultures as well as in sterile water. SPM-bacteria inhibit methyl transfer to mercury(II) ions. This is not only due to passive adsorption processes of mercury(II) to bacterial cell walls; methylmercury is also decomposed very rapidly by SPM-bacteria and is immobilized as mercury(II) by the cells.

Polymeric organosilicon systems 14. Synthesis and some properties of alternating polymers composed of a dithienylene group and a mono-, di- or tri-silanylene unit

Abstract: Poly[5, 5′ - (dimethylsilylene) - 2, 2′ - dithienylene] (4a), poly[5, 5′ -(methylphenylsilylene)-2, 2′ -dithienylene] (4b), poly[5, 5′ -(1, 1, 2, 2-tetramethyldisilanylene)-2, 2′ -dithienylene] (4c), poly[5, 5′-(1, 2-dimethyl-1, 2-diphenyldisilanylene)-2, 2′ -dithienylene] (4d), poly[5, 5′-(1, 2, 2, 2-tetramethyldisilanylene)-2, 2′-dithienylene] (4e), and poly[5, 5′-(1, 1, 2, 2, 3, 3 - hexamethyltrisilanylene) - 2, 2′ -dithienylene] were synthesized by dehalogenative coupling of the respective bis(2-bromothienyl)- substituted mono, di- and tri-silanes with magnesium in the presence of a catalytic amount of a nickel(II) complex in 16–99% yields. The polymers thus obtained are light-yellow solids and soluble in common organic solvents. Molecular weights, Mw, of the polymers were measured and found to be 7800–35 000 by gel-permeation chromatography relative to polystyrene standards. The photochemical properties of the polymers (4a–4d) having silylene and disilanylene units were investigated. Only poly[5, 5′-(1, 2-dimethyl-1, 2-diphenyl-disilanylene)-2, 2′-dithienylene] (4d) was found to be photoactive, but the others were inactive. When the thin solid films prepared from the polymers 4a–4e by spin-coating were exposed to antimony(V) fluoride in vacuo, the films became conducting; their conductivities were determined to be 10−2 – 10−3 S cm−1 by the four-probe method.

Speciation of butyltin compounds by ion chromatography coupled to electrothermal atomic absorption spectrometry

Abstract: A new method for the determination of butyltin species by ion-exchange chromatography linked with graphite-furnace electrothermal atomic absorption spectrometry (ETAAS) is presented. The separation is achieved on a strong cation-exchange column with a 0.18 mol dm−3 solution of diammonium citrate at pH 6.5 with a step change to pH 4.0 in 60:40 methanol/water solvent. ETAAS detection is performed on-line using an oxidizing matrix modifier. Mono-, di- and tri-butyltin may be determined in a single experiment with detection limits of (respectively) 0.5, 1.1 and 0.8 ng (Sn). Applications to actual samples are reported.

The biotransformation of monomethylarsonate and dimethylarsinate into arsenobetaine in seawater and mussels

Abstract: Water-soluble 3H-labeled arsenic compounds were phenol-extracted from mussels (Mytilus edulis) and seawater after exposure to [3H]monomethylarsonate (MMAA) and [3H]dimethylarsinate (DMAA). Varying amounts of [3H] arsenobetaine were found in mussels and seawater, depending upon the experimental conditions. The results indicate that arsenobetaine is principally biosynthesized by microscopic organisms in the seawater and that it is bioaccumulated by mussels. Total arsenic concentrations in mussel flesh, byssal threads and shells were also determined, showing concentration increases in all three compartments.

Diorganotin(IV) dipeptide complexes with potential antitumour activity

Abstract: A series of complexes of the dimethylltin(IV) moiety with dipeptides has been synthesized. The dipeptides are L-alanyl-L-histidine (H2AlaHis), L-methionyl-L-methionine (H2MetMet), L-glycyl-L-histidine (H2GlyHis) and L-histidyl-L-glycine (H2HisGly). The complexes have been characterized by IR and 119Sn Mossbauer spectroscopy in the solid state and by 1H NMR in CD3OD and D2O solutions. They consist of monomeric entities, with the tin atom arranged in a pentacoordinated trigonal bipyramidal structure. The dipeptides are coordinated via the amino group, deprotonated peptide nitrogen and carboxylate group. Neither imidazole in histidine-containing dipetides, nor the thioether group in MetMet, is involved in bonding; they act as pendant arms on the outer surface of the complexes.