Electrochemical behaviour of organotin compounds: Part III. Dialkyltin mercaptocarboxylates

Electrochemical behaviour of di-n-octyltin dithioglycolate has been investigated in acetate buffer (pH 7.0) containing 80% (v/v) ethanol. It has been found to give two well-defined polarographic waves, one of which is anodic and involves two-electron oxidation of the mercaptide. The other wave has been found to be cathodic and is due to one-electron reduction of the dioctyltin compound to a free radical. Strong adsorption of the compound at the DME was indicated by depression in its drop time curve. A mechanism of the electrode process is postulated and a method for detection of these compounds down to p.p.m. level has been developed.     

Electrochemical behaviour of organolead compounds: Part I. Triphenyl-lead acetate

The electrochemical behaviour of triphenyl-lead acetate in 50% (v/v) ethanol has been investigated using various electrochemical techniques including polarography, cyclic voltammetry and controlled potential coulometry. It has been found to give three/four polarographic waves. The first normal wave involves an one-electron irreversible reduction of triphenyl-lead ions giving triphenyl-lead free radicals which are strongly adsorbed at the DME giving rise to an adsorption prewave. The triphenyl-lead free radicals produced in the normal reduction step immediately react with mercury of the DME producing phenylmercury radicals and metallic lead. Wave II has been ascribed to the simultaneous reduction of triphenyl-lead free radicals and phenylmercury free radicals. The metallic lead produced in these processes undergoes oxidation at the electrode and “distorts” the “normal” adsorption prewave of step I. A mechanism of reduction is proposed and polarographic methods have been developed for determining triphenyl-lead compounds at ordinary level and down to submicromolar level.     

Exchange reactions between organotin compounds and thallium trichloride

Summary A study was made of the exchange reactions between thallium trichloride and tetraethyl-, tetrabutyl-, tetraphenyl-, tetra-o-tolyl-, tetra-p-tolyl-, tetrakis-o-methoxyphenyl-, tetra-cis-propenyl-, tetra-trans-propenyl-, tetraisopropenyl-, and tetravinyl-tins, and the reaction products were characterized.     

Polarographic behaviour of some organotin(IV) compounds in dimethyl sulphoxide

The differential pulse polarographic behaviour in dimethyl sulphoxide (DMSO) of 14 organotin(IV) compounds having the general formula R₃SnX (R = Me, Ph; X^? = NCS^?, N₃^?, N₃^?, NO₃^?, OH^?, NCO^? and OAc^?) and ⁿBu₃SnCl and ⁿBu₂SnCl₂ has been studied. The peak potential was found to depend markedly on the organic group and to a lesser extent on the nature of the anion X. The phenyltin compounds were reduced at lower potentials than the corresponding methyltin compounds. The data obtained could be used for trace determination of these compounds. Linear calibration curves were obtained over the concentration range of 2.8 × 10^?4 to 1.9 × 10^?6 mol dm^?3.     

Electrochemical preparation of some organotin compounds

Organotin dihalides R₂SnX₂ (X  Cl, Br, I) and their adducts with bidentate donor ligands have been prepared in high yield by the direct electrochemical reaction of metallic tin with alkyl or aryl halides in organic media at room temperature. Dimethyltin diiodide can be converted to tetramethyltin by reaction with methyl iodide at a cadmium anode. Electrochemical halide abstraction has been used to prepare R₆Sn₂ (R  Me, Ph) from the corresponding R₃Sn halide. The mechanism of these reactions is discussed.     

Electrochemical reactions of organic compounds in liquid ammonia: Part IV. Reduction of cyclooctatetraene

The electroreduction of COT in liquid ammonia at ?38° and ?65°C was investigated by cyclic voltammetric and controlled potential coulometric techniques. The results are interpreted by a two-step two-electron transfer reaction with strong ion-pairing of the COT dianion. Values for the heterogeneous electron transfer rate constants and the equilibrium constant of the disproportionation of the radical anion are estimated, based on a digital simulation of the cyclic voltammogram.     

Reduction of dicarbonyl compounds on the dme: Part VII. Electrochemical behaviour of glyoxal

Polagraphic and kinetic studies of both the first and the second reduction waves of glyoxal have been carried out in aqueous solutions in the pH range 0 – 11.Tafel slopes and reaction orders with respect to glyoxal, H⁺ ion and proton donors present in solutions have been obtained at potentials corresponding to the foot of the waves. Reactions mechanisms are proposed for this potential zone.The proposed mechanism accounts both for our experimental data and for those previously reported in the literature.     

Sulphur substituted organotin compounds. Part 6. Reactions of mercaptomethyltin compounds with arenesulphenyl chlorides

Reactions between Ph₃SnCH₂SAr and 2-NO₂C₆H₄SC? lead to the formation of 2-(ArSCH₂-6-NO₂C₆H₃SSC₆H₄NO₂-2 via the [2,3]sigmatropic rearrangement of the S-arylthio-sulphonium ylides $\text{C}$H₂$\text{S}\text{+}$(Ar)SC₆H₄NO₂2.     

Antimicrobial activity of organotin(IV) compounds: a review

A comprehensive review on antimicrobial activity of organotin(IV) compounds is presented. Copyright © 2008 John Wiley & Sons, Ltd.     

Carbon-13 NMR studies of some organotin(IV) compounds

The ¹³C chemical shifts and ¹³C−¹¹⁹Sn, ¹¹⁷Sn coupling constants for several organotin(IV) compounds R_xSnCl_4−x (R = Me, Buⁿ, Ph; x = 1−4) have been measured in both inert (CDCl₃) and donor (DMSO-d₆) solvents, as have ¹³C data for the compounds R_xSnR′_4−x (R = Me, Ph; R′ = Buⁿ and R = Me; R′ = Ph; x = 1−3) and the compounds Me₃SnX (X = pseudo halide). The δ and ¹J(C-Sn) values appear to depend mainly on the type and number of substituents on tin and the donor ability of the solvent. There are linear relationships between the number of substituents (x) and both δ and ¹J(C-¹¹⁹Sn) for almost the R_xSnX_4−x series (R = Me, Buⁿ, Ph; X = Cl and R = Me, Buⁿ; X = Ph; x = 1−4), when measured in a single solvent, e.g. CDCl₃. There is an excellent linear relationship between ¹J(C-¹¹⁹Sn) and ²J(¹HC-¹¹⁹Sn) for the compounds Me_xSnCl_4−x. Determination of ¹³C data for Me₃SnCl and Ph₃SnCl in a range of solvents reveals that the value of ¹J(C-Sn) increases with the donor ability of the solvent.The marked increase in the values of ¹J(C-¹¹⁹Sn) in DMSO-d₆ for the compounds R_xSnCl_4−x(R = Me, Buⁿ,Ph) on going progressively from x = 4 to x = suggest tin coordination numbers of 4, 5, 6 and 6, respectively. Some additional physical data are presented for the isolated complexes from DMSO and the compounds Ph_xSnCl_4−x(x = 1−3) and Me₃SnX with X = N₃ or OCOMe.     

Electrochemical cyclization of unsaturated hydroxy compounds. Part I. Phenylselenoetherification

One-step cyclization of alkenols has been accomplished by electrooxidative phenylselenoetherification. The reaction was performed by electrolysis of unsaturated alcohols and diphenyl diselenide in methylene chloride containing tetraethylammonium bromide.     

Electrochemical cyclization of unsaturated hydroxy compounds. Part II. Phenylselenolactonization

Phenylselenolactonization was performed, in one step, by electrolysis of Δ4- and Δ5 -unsaturated carboxylic acids and diphenyl diselenide in methanol containing ammonium bromide.     

Mössbauer spectra of organotin compounds : VI. Dithiolatotin compounds

The Mössbauer spectra of a wide range of organo(dithiolato)tin compounds R₂Sn(SR′)₂ have been measured. A comparison of calculated quadrupole splittings with the observed values has enabled structures to be assigned. Tetrahedral configurations occur in most of the compounds, the thiocetates (and probably the mercaptoacetates) being exceptional in having octahedral structures.     

A multicriteria ranking of organotin(IV) compounds with fungicidal properties

The application of multicriteria decision‐making methods to the results of in vitro antifungal properties of organotin compounds of the type Ph_xSnX_z (x = 2 or 3; X = O₂CC₆H₄OH, O₂CC₆H₄OCOCH₃, Cl or O₂CCH₃; z = 1 or 2) and of free 2‐hydroxybenzoic and 2‐acetoxybenzoic acids against Aspergillus niger, Aspergillus flavus, Candida albicans, Penicillium citrinum, Trichophyton rubrum and Trichophyton violaceum have been described. Ranking information necessary to select one toxicant in preference to others and to assess the properties influencing the preference has been obtained. Patterns in the multivariate analyses suggest that cationic and anionic moieties of the toxicant play some roles in their fungicidal activities. The triphenyltin compounds were generally more active than their diphenyltin analogues, but the acetoxybenzoates were more active than the corresponding hydroxybenzoates, acetates or chlorides. Thus, triphenyltin acetoxybenzoate is up to 7.5 times as active as the corresponding acetate, which is commercially marketed as a fungicide. The results of the analyses have been discussed in the light of the mechanism of antifungal activity of organotin compounds and the potential of multivariate data analysis techniques to facilitate the screening and ranking of antifungal agents. Copyright © 2003 John Wiley & Sons, Ltd.     

Studies on organotin compounds using the Del Re method : VIII. Mössbauer spectra or organotin compounds

A method for calculating the electron density at the nucleus of the tin atom in a tetravalent compound has been developed using the quantities available from the Del Re calculations. The calculated electron densities show a fair correlation with the experimental Mössbauer isomer shifts, and a value of +3.2 × 10^?4 is obtained for (ΔR/R), in excellent agreement with the value +3.30 × 10^?4 obtained from an independent method using internal electron conversion measurements. By defining an assymmetry parameter, A, which is a measure of the deviation of the calculated p-electron distribution from the hypothetical spherically-symmetric distribution, in which the p-electron would be distributed equally between the three p-orbitals, the experimental quadrupole splittings have been correlated and interpreted. Factors governing the magnitude of quadrupole splitting are also discussed.     

Electrochemical investigation of nucleic acid behaviour: Part I. Native calf thymus DNA

The polarographic behaviour of DNA extracted from the calf thymus has been studied using phase sensitive a.c. polarography. The conditions of adsorption on the dropping mercury electrode have been studied in terms of the conditions of medium (ionic strength, pH) and of the molecular weight of DNA. The ionic strength plays a deciding role in the conditions of adsorption. The adsorption also depends on the form of the macromolecule. When it is in rod form (low molecular weight) the adsorption occurs parallel to the charged surface. When it adopts a wormlike form, loops are formed which extend into the solution. The adsorption does not depend on the nature of the monovalent counterion thus the adsorption is identical in Na⁺ and NH₄⁺ media.The polarograms of native and denatured DNA present an initial rounded peak situated at the limit of the adsorption zone. The native DNA is characterised by a second peak which appears, whatever the medium and the molecular weight of the DNA may be, on the recordings of the in-phase component of the current. This peak is situated at a more positive potential than that which is normally characteristic of the denatured DNA.The characteristics of the peaks of the native DNA have been specified. The first peak corresponds to the desorption of a certain number of adsorbed elements of the macromolecule. The second peak changes its properties according to the pH. In a slightly acid medium, it corresponds to the reduction of the adsorbed bases without desorption of the reduced products. The zones of reduction are the locally destabilized, i.e. the A-T rich regions of the DNA. In alkaline medium it corresponds to the desorption of the macromolecule. A general schema of the behaviour of native DNA on the dropping mercury electrode is proposed.     

Biological activity studies on organotin(IV) complexes and parent compounds

This review summarized the literature and own data on the parent organotin(IV) compounds and complexes formed with biologically active ligands.     

Studies on organotin compounds using the Del Re method : VII. Bond polarisability index and reactivity of organotin compounds

Using the Del Re method a simple reactivity index, defined as the bond polarisability index, has been derived. The observed reactivity sequence for the cleavage of the alkyl groups from the metalalkyls both in the polar and in the non-polar solvents have been interpreted, and the relative rates of these reactions correlated with this index. The relative rates of the exchange reactions between trialkylaluminium and trialkyltin hydrides have also been satisfactorily interpreted.     

Melt polymerization of hexachlorocyclotriphosphazene in the presence of organotin (IV) compounds

The melt polymerization of hexachlorocyclotriphosphazene to poly(dichlorophosphazene) has been studied in the presence of organotin (IV) compounds. Unlike other typical Lewis acids, diethyltin (IV) chloride, Et₂SnCl₂, has shown to be an inhibitor for the thermal polymerization of the trimer, raising the activation energy to 70 kcal/mol. Diethyltin(IV) chloride remarkably delayed the rate of polymerization and efficiently inhibited the crosslinking reaction, thus leading to an improvement in the yield of the linear polymer without sacrifice to its molecular weight. © 1993 John Wiley & Sons, Inc.