James McManus

Nuclear magnetic resonance and structural investigations of the chemistry of organotin compounds: II. 119Sn NMR investigations of the pyrazine adducts of dialkyltin(IV) dihalides

Abstract The interactions of SnR 2 X 2 (R  Me, Et, n Pr, n Bu; X  Cl, Br, NCS) with pyrazine (L) have been investigated in both chloroform and acetonitrile. Equilibrium constants have been determined by using 119 Sn chemical shifts and the computer program eqnmr . In chloroform, Sn n Bu 2 Cl 2 and Sn n Bu 2 Br 2 form complexes of composition ML and ML 2 , with ML the dominant species. In acetonitrile all of the tin(IV) complexes form only the 1:1 adducts (ML). Thermodynamic parameters have been determined for these systems in both solvents.

31P NMR study of the interaction of a commercial succinimide-type lubricating oil dispersant with zinc(II) bis(O,O'-di-iso-butyldithiophosphate)

Abstract 31 P nuclear magnetic resonance (NMR) spectroscopy has been employed to study the interactions between zinc(II) bis(O,O′-di-iso-butyldithiophosphate) and a commercial poly(isobutenyl)succinimide polyamine dispersant at both ambient and subambient (213–293 K) temperatures. The major species in solutions containing high N:Zn ratios is a complex between the two components in which only two nitrogen atoms of the polyamine dispersant are bonded to the zinc.

Nuclear magnetic resonance studies and structural investigations of the chemistry of organotin compounds: Part I. 119Sn NMR studies of the pyrazine adducts of some organotin compounds

Abstract A procedure is described for the analysis of the concentration dependence of NMR chemical shift data on the chemical equilibria present in solution. This procedure has been used to study the equilibrium between SnMe 3 Cl and 4-methylpyridine in benzene, and the values obtained for the thermodynamic parameters are in good agreement with those previously determined by a calorimetric method. The equilibria of the adduct formation reactions of SnPh 2 Cl 2 , SnPh 2 Br 2 and SnPh 2 I 2 with pyrazine in chloroform and acetonitrile have also been investigated. In chloroform solution, both 1:1 and 1:2 (M:L) adducts are formed, whereas only 1:1 adducts are formed in acetonitrile under the experimental conditions used. For all three organotin compounds the interactions are relatively weak. The Lewis acidity of the SnPh 2 X 2 organotin species decreases in the order Cl > Br > I.

31P nuclear magnetic resonance study of the interaction of multidentate amines with zinc(II) bis(O,O′-di-iso-butyldithiophosphate)

31P NMR has been employed to study the interaction between zinc(II) bis(O,O′-di-iso-butyldithiophosphate), Zn[S2P(OiBu)2]2, and four multidentate amines (diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine) in chloroform at 294 K. The major interaction of Zn[S2P(OiBu)2]2 and these polyamines involves displacement of the {S2P(OiBu)2} ligands from the zinc giving [Zn(amine)]2+ and [S2P(OiBu)2]− ions in solution. The magnitudes of the equilibrium constants, K1 (=[{Zn(amine)}2+][{DDP}−]2/[Zn(DDP)2][amine]), have been evaluated in the cases of triethylenetetramine (20.0 l mol−1), tetraethylenepentamine (19.1 l mol−1) and pentaethylenehexamine (1.58 l mol−1). Crystalline 1:1 ionic complexes have also been isolated from these systems and characterised.

Fourier-transform infrared study of the oxidative thermolysis of tetramethyltin in the temperature range 533–613 K

The kinetics of the oxidative thermolysis of tetramethyltin have been investigated in the temperature range 533–613 K using Fourier-transform infrared spectroscopy. Even in the presence of a large molar excess of oxygen (molar ratio Me4Sn : O2≈ 1 : 9), the gaseous reaction products were methane (2.6 mol) and carbon dioxide (1.4 mol). Small amounts of transient methanol and formaldehyde were also observed in the gas phase. The disappearance of tetramethyltin follows zero-order kinetics, with rate constants varying from 1.19 × 10–8 mol dm–3 s–1 at 533 K to 29.9 × 10–8 mol dm–3 s–1 at 613 K. The activation energy is determined to be 116(6) kJ mol–1. The data are interpreted in terms of a surface-mediated process. The rate-determining step is proposed to be the dissociative chemisorption of a tetramethyltin molecule at two adjacent surface oxygen sites, giving a surface trimethylstannyloxy, 1-OSnMe3, species and surface methoxide. Subsequently, the predominant process is the stepwise electrophilic cleavage of the tin–carbon bonds of the surface trimethylstannyloxy species by surface hydroxyl groups producing methane. Carbon dioxide is produced by the oxidation of the surface methoxide.

Fluorescence study of Bovine Serum Albumin and Ti and Sn Oxide Nanoparticles Interactions.

Nanochemistry offers stimulating opportunities for a wide variety of applications in the biosciences. Understanding of the interaction of nanoparticles with biomolecules such as proteins is very important as it can help better design and fabricate nanocomposites for applications in diagnostics, drug delivery, and cell monitoring. In this work, the interaction of Bovine Serum Albumin (BSA) and two types of metal oxide nanoparticles (titanium and tin) have been studied using the intrinsic fluorescence of tryptophan residue from the proteins measured by steady state and time resolved fluorescence techniques. The nanoparticles which were fabricated using a novel synthetic process have average sizes of ∼2 nm (SnO 2 ) and ∼6 nm (estimated for TiO 2 ) and have very high solubilities in a variety of solvents. The Stem-Volmer plots indicate an effective quenching process by TiO 2 nanoparticles whereas SnO 2 nanoparticles have a lower quenching efficiency for BSA fluorescence. Static quenching is the major contribution in the overall process which may indicate a high degree of association between protein and nanoparticles. The difference in BSA fluorescence quenching efficiency between the two types of nanoparticles can be explained by the non-covalent interaction differences and the thermal stability of protein-nanoparticle associated species for both materials.

Investigation of the hydrolysis of [Sn(CH3)3(H2O)2]+ in aqueous solution by tin-119 nuclear magnetic resonance spectroscopy

The hydrolysis of [Sn(CH3)3(H2O)2]+ has been investigated using 119Sn NMR spectroscopy in aqueous solution at 25°C and ionic strength 0.5 mol dm–3. The ionic strength was adjusted using KCl, KNO3 or NaClO4. The chemical-shift data were processed using the computer program EQNMR to yield the stability constants and the chemical shifts of the various species present in solution. The results are compared with literature data obtained using other techniques.

On the role of the solid–gas interface in the thermolysis of trimethylgermane and trimethylstannane

Metal film surfaces have a profound effect on the thermal decomposition of Me3MH (M = Ge and Sn), both of which unusually decompose by half-order kinetics at elevated temperature.

The nature of zinc(II) bis(O,O′-dialkyl dithiophosphates) in ethanol: complexation or ionisation?

Abstract 31 P NMR chemical shift data have been recorded for eight zinc(II) bis( O , O ′-dialkyl dithiophosphates) (Zn(S 2 P(OR) 2 ) 2 ) (R=n-Bu, iso-Bu, sec-Bu, n-Pent, n-Hex, n-Oct, n-Non and n-Dec) in ethanol. Apart from sec-BuZnDDP which exhibits a chemical shift of c . 100.1 ppm, the chemical shifts in ethanol solution are essentially independent of the alkyl group and fall in the narrow range 103.3–104.0 ppm in the concentration range 0–0.1 M. The conductance of both n-BuZnDDP and n-HexZnDDP in ethanol increases smoothly and steadily with increasing concentration. In toluene, however, the conductance of both is three or four orders of magnitude lower than in ethanol and very similar to that of neat toluene, indicating that in ethanol some ionisation of the DDP ligands occurs, whereas toluene solutions are non-conducting. Ethanol solutions of ZnDDPs comprise principally adducts of the type Zn(S 2 P(OR) 2 ) 2 ·2EtOH, superimposed on which is a small extent of ionisation.

An X-ray crystallographic investigation of the structures of pyrazine adducts of diphenyltin dichloride and dimethyltin dichloride

Reaction of SnPh2Cl2 with pyrazine (pyz) leads exclusively to the formation of an adduct having the bulk composition SnPh2Cl2·0.75pyz. It has a structure composed of layers in which zig-zag polymeric chains, (SnPh2Cl2·pyz)n, with six-co-ordinate tin, alternate with layers containing non-interacting molecules of (SnPh2Cl2)2·pyz, with five-co-ordinate tin. The Sn–N bond lengths are abnormally long; each tin atom tin atom in the polymeric chains has Sn–N bond lengths of 2.961(10) and 2.783(10)A, and the Sn–N bond length in (SnPh2Cl2)2·pyz is 2.683(11)A. Mossbauer spectroscopy does not identify the presence of the two tin sites in the solid whereas 119Sn n.m.r. does. X-Ray crystallographic details are: space group Pbam(orthorhombic), a= 14.935(2), b= 13.409(3), c= 14.959(3)A, Z= 8(Sn), R= 0.047 (R′= 0.056) for 1 478 observed reflections with I > 3σ(I). Reaction of SnMe2Cl2 with pyrazine leads exclusively to formation of the adduct (SnMe2Cl2)2·pyz; the distannoxane (SnMe2Cl)2O is also formed if solutions are not protected from the atmosphere. The adduct has a chain polymeric structure with six-co-ordinate tin atoms alternatively linked by chloride ions and pyrazine molecules. The Sn–N bond length [2.746(6)A] is abnormally long. The polymeric chains pack into well defined planes, with chains in alternate planes propagating in orthogonal directions. Crystallographic details are: space group P21/n(monoclinic), a= 6.855(1), b= 10.344(2), c= 12.014(3)A, β= 92.590(7)°, Z= 2, R= 0.03 (R′= 0.033) for 727 observed reflections with I > 3σ(I).