New organotin catalysts in urethane and polyurethane technology

The use of organotin α-substituted alcohols and carbamates as catalysts has been investigated in urethane and polyurethane preparations. These compounds have been shown to be new and very active catalysts. The mechanism of the reaction has been studied.     

The toxic effects of organometals on the lands cycle in HL-60 cells

The concentration of free fatty acids within cells is mainly dependent upon the following enzyme activities: liberation by phospholipase A₂ (PLA₂), activation of free acids by acyl-CoA-synthetase and re-esterification by lysophospholipid acyltransferase (LAT). In many cell types, especially those of the haematopeotic system, this deacylation-reacylation cycle (‘Lands cycle’) plays an important role in the regulation of free fatty acid concentration, above all that of arachidonic acid. We have shown here that heavy-metal compounds affect this cycle mainly at two points and thereby lead to an increase of free fatty acids. On the one hand, organometals cause an inhibition of the reacylation of lysophospholipids; and on the other, the induction of PLA₂ activity produces the same result. All compounds investigated such as methylmercury chloride (MeHgCl), diethyltriethyl-, and trimethyl-lead chloride (Et₂PbCl₂, Et₃PbCl, Me₃PbCl) as well as trimethyltin chloride (Et₃SnCl) and di-t-butyltin dichloride (t-Bu₂SnCl₂) show at least one of these effects. In the case of Et₃PbCl, the use of PLA₂-inhibitors or pertussis toxin causes a drastic decrease in the amount of arachidonic acid liberated. These experiments demonstrate that the organometallic compounds inhibit the reacylation and/or stimulate the deacylation of fatty acids that are involved in many important biological or pathological mechanisms. The results suggest that in differentiated HL-60 cells the organometal compounds stimulate the Lands cycle by increasing the activity of the PLA₂, possibly via a signal-transduction mechanism, and this effect is intensified via an inhibition of reesterification.     

Effects of sodium concentration on the morphology and rheological behaviour of alkoxide-carboxylate co-ionomeric mixtures of phenoxy and ethylene terpolymers

Mixtures at various weight ratios of phenoxy (PH) and a terpolymer of ethylene tert. butyl acrylate-acrylic acid (EAA) were prepared in a Brabender Plasticorder in the presence of different amounts of sodium ethoxide (NaOEt). The mixtures were examined by SEM, DSC, and dynamic rheometry.While the crystallisation characteristics of EAA were affected only to a small extent by the addition of NAOEt, the corresponding mixtures with phenoxy acquired an increasingly more pronounced amorphous nature by increasing the concentration of NaOEt.SEM examinations revealed that the morphology of the mixtures became more homogeneous when NaOEt was present. This was manifested also by a change from dual relaxations to single relaxations in the Cole-Cole plots of the rheological data.     

Crystal structure and fungitoxicity of aquatributyltin N-phthaloylglycinate

The [nBu₃Sn(N-phthaloylglycinate)(OH₂)] compound has been prepared and characterized. The crystal structure reveals the tin atom, in each of the two molecules comprising the asymmetric unit, to exist in a distorted trigonal bipyramidal geometry in which the trigonal plane is defined by the three organic substituents and the axial sites are occupied by an oxygen atom derived from a monodentate carboxylate ligand and a coordinated water molecule. The [nBu₃Sn(N-phthaloylglycinate)(OH₂)] compound and three other triorganotin derivatives of N-phthaloyl-protected amino acids display marked toxicity against several economically important plant pathogenic fungi.     

Ultrasonic enhancement of electrochemiluminescence from arylacetate electrooxidation

This paper describes the previously unreported electrogenerated chemiluminescence (ECL) from the electro-oxidation of several aryl carboxylates at a platinum flag electrode in aqueous, methanolic and acetonitrile solutions using tetramethylammonium hydroxides as a supporting electrolyte. In most cases electrochemiluminescence was markedly enhanced by simultaneous irradiation with ultrasound during electrolysis. Increase in electrochemiluminescence intensity with electrolysis current and carboxylate concentration was observed. Addition of a radical scavenger or purging of the solution with oxygen lowers ECL emission intensity. In contrast the presence of oxygen enhances the intensity of sonoluminescence, which is a concurrent but weaker process occurring under ultrasonic irradiation alone. Ring-substituted phenylacetates almost always produced less electrochemiluminescence than the unsubstituted parent molecule, though within the substituents studied chloro-substituted phenylacetates produced more ECL intensity than either methoxy- or nitro-substituted derivatives.     

Synthesis,characterization and in-vitro antitumour activity of dibutyltin carboxylates involving the perfluorophenyl moiety: Crystal structure of the dimeric bis[(4-fluoro- and pentafluoro-benzoato)di-n-butyltin] oxides

Crystal structure determinations of {[(F₅C₆COO)Bu₂Sn]₂O}₂ and {[(4-F-C₆H₄COO)-Bu₂Sn]₂O}₂ show that the structures are similar and feature central Bu₄Sn₂O₂ units with two Bu₂Sn groups connected by bridging oxygen atoms. Each pair of exo- and endo-cyclic tin atoms is linked by an almost symmetrically bridging carboxylate group, with the two remaining groups attached to the exocyclic tin atom only. Crystals of {[(F₅C₆COO)Bu₂Sn]₂O}₂ are triclinic, space group P1, with unit cell dimensions a = 12.425(3) Å, b = 13.090(5) Å, c = 11.697(3) Å, α = 95.31(3)°, β = 93.28(2)°, γ = 113.01(2)°, V = 1734(1) ų, Z = 1. Crystals of {[(4-F-C₆H₄COO)Bu₂Sn]₂O}₂, are also triclinic, space group PI, a = 12.599(6) Å, b= 25.359(4) Å, c = 11.480(4) Å, α = 91.44(3)°, β = 114.77(3)°, γ=97.43(3)°, V=3289(2) ų, Z=2. The structures were refined to final R= 0.046, R_w = 0.046 for 4312 reflections with I≥ 3.0 σ(l) for {[(F₅C₆COO)Bu₂Sn]₂O}₂ and R=0.061, R_w=0.068 for 4112 reflections with l≥3.0 σ(l for {[(4-F-C₆H₄COO)Bu₂Sn]₂O}₂.     

Crystallographic report: 1,3‐Bis[(trimethylsilylmethyl)dichlorostannyl]propane, [(Me3SiCH2)Cl2Sn]2(CH2)3

The dinuclear molecule of [(Me₃SiCH₂)Cl₂Sn]₂(CH₂)₃ adopts an extended conformation and features distorted tetrahedral tin centres, with the greatest distortion manifested in the C? Sn? C angles of approximately 128 °. The distortions are ascribed to the influence of intermolecular Sn···Cl interactions. Copyright © 2002 John Wiley & Sons, Ltd.     

Biocidal organotin compounds: Part 1. Preparation and characterization of triorganotin(IV) 4-pyridyl- and 2-pyrimidyl- thioacetates and the crystal structure of triphenyltin(2-pyrimidylthioacetate)

The preparation and spectroscopic characterization of [R₃Sn(O₂CCH₂SC₅H₄N-4)], R == Ph, benzyl (Bz), cyclohexyl (c-Hex) and n-Bu, and of [R₃Sn(O₂CCH₂SC₄H₃N₂-2,6)], R == Me, Ph and n-Bu, are reported. The 2-pyrimidyl compounds feature trigonal bipyramidal tin centres with trans-R₃SnO₂ geometries as was confirmed by X-ray crystallography for [Ph₃Sn(O₂CCH₂SC₄H₃N₂-2,6)]. ¶ By contrast the 4-pyridyl compounds have trigonal bipyramidal geometries in the solid state (arising from intermolecular Sn…N interaction) and tetrahedral geometries in solution. The biocidal activity of these compounds against the fungi Helminthosporium maydis (ITCC 2675) and H. oryzae (ITCC 2675), both of which damage crops such as maize and rice, shows promise. Encouraging is the observation that the compounds show no adverse phytotoxicity at concentrations to 10^?3M.