Extending distannoxane double ladders using rigid spacers: a double ladder with eight chiral tin atoms-and a twist!

The new bulky silicon-containing ditin precursor p-(RCl₂SnCH₂SiMe₂)₂C₆H₄ (R = CH₂SiMe₃ (4)) has been synthesized and further reacted to form a unique double ladder {[p-(R(Cl)SnCH₂SiMe₂)₂C₆H₄]O}₄ (6). The two layers within 6 are twisted with respect to one another, resulting in a helical motif and a total absence of molecular symmetry so that there are eight chiral tin atoms within the system. The structure is compared to the double ladder {[m-(R(Cl)SnCH₂CH₂)₂C₆H₄]O}₄ (11), which was prepared from the less sterically demanding ditin precursor m-(RCl₂SnCH₂CH₂)₂C₆H₄ (10). The two layers within 11 are parallel, and the molecule contains only two kinds of tin atom.

Steric control over molecular structure and supramolecular association exerted by tin- and ligand-bound groups in diorganotin carboxylates

Structural data (X-ray and solution and solid-state ^₁₁₉Sn NMR) show that skew-trapezoidal-bipyramidal diorganotin compounds of 2-quinaldate are invariably monomeric, owing to the steric bulk of the carboxylate ligand. In contrast, most of the analogous compounds of 2-picolinate (2-pic) can increase their coordination number by polymerization or the incorporation of solvent in their coordination sphere in the solid state. The exceptional compound is tBu₂Sn(2-pic)₂ (3), for which no increase in coordination number is apparent, a result that is correlated with the bulky tert-butyl groups. Thus, judicious choice of tin or ligand substituents can be exploited to dictate coordination number and/or the degree of supramolecular aggregation in the investigated systems.

Synthesis, molecular structure, and isomerisation in solution of (Me3SbS)2Me2SnCl2. Concomitant hypercoordination of tin and antimony

The reaction of Me₃SbCl₂ and (Me₂SnS)₃ afforded the complex (Me₃SbS)₂Me₂SnCl₂ in high yields, whose molecular structure features both hypercoordinated tin and antimony atoms. In solution, (Me₃SbS)₂Me₂SnCl₂ undergoes a reversible dissociation and ligand interchange reaction to give Me₃SbS, Me₃SbCl₂ and (Me₂SnS)₃.

Hydrolysis of bis((trimethylsilyl)methyl)tin dihalides. Crystallographic and spectroscopic study of the hydrolysis pathway

The synthesis and characterization by multinuclear NMR spectroscopy of the diorganotin dihalides (Me₃SiCH₂)₂SnX₂ (1, X = Cl; 2, X = Br), the diorganotin dichloride water adduct (Me₃SiCH₂)₂SnCl₂·H₂O (1a), the dimeric tetraorganodistannoxanes [(Me₃SiCH₂)₂(X)SnOSn(Y)(CH₂SiMe₃)₂]₂ (3, X = Y = Cl; 4, X = Br, Y = OH; 5, X = Br, Y = F; 6, X = Y = OH; 8, X = Cl, Y = OH), and the molecular diorganotin oxide cyclo-[(Me₃SiCH₂)₂SnO]₃ (7) are reported. The structures in the solid state of compounds 1a, 3, 6, and 7 were determined by single-crystal X-ray analysis. In toluene solution, the hydroxy-substituted tetraorganodistannoxane 6 is in equilibrium with the diorganotin oxide 7 and water. The eight-membered diorganotin oxide cyclo-[(Me₃SiCH₂)₂SnO]₄ (7a) is proposed to be involved in this equilibrium. On the basis of the results of this and previous works, a general hydrolysis pathway is developed for diorganotin dichlorides containing reasonably bulky substituents.

Novel 10- and 20- membered tin- and silicon-containing rings: synthesis, complexation behavior and conversion into a lewis acidic polymer

Reaction of the dimethylsilylmethyl-substituted tetraorganotin derivative CH₂[CH₂Sn(Ph₂)CH₂Si(H)Me₂]₂ (1) and CH₂[CH₂Sn(Ph₂)CH₂Si(i-PrO)Me₂]₂ (3), respectively, with mercuric chloride afforded the novel silicon- and tin-containing 10- and 20-membered rings cyclo-CH₂[CH₂Sn(Cl₂)CH₂Si(Me₂)]₂O (4) and cyclo-CH₂[CH₂Sn(Cl₂)CH₂Si(Me₂)OSi(Me₂)CH₂Sn(Cl₂)CH₂]₂CH₂ (5). Both compounds 4 and 5 can be converted into the soluble Lewis acidic polymer poly-[Si(Me₂)CH₂Sn(Cl₂)(CH₂)₃Sn(Cl₂)CH₂Si(Me₂)O] (8). ¹¹⁹Sn NMR studies indicate that 4 acts as a bidentate Lewis acid toward chloride ions, exclusively forming the 1:1 complex [cyclo-CH₂[CH₂Sn(Cl₂)CH₂Si(Me₂)]₂O·Cl]-[(Ph₃P)₂N]⁺ (7). The molecular structures as determined by single-crystal X-ray diffraction analysis of 4 and 7 are reported.

Reducing the macroparticle content of cathodic arc evaporated TiN coatings

Cathodic arc evaporation (CAE) is a widely used technique for generating highly ionised plasma from which hard, wear-resistant PVD coatings can be deposited. A major drawback of this technique is the emission of micrometer-sized droplets of cathode material from the arc spot, which are commonly referred to as ‘macroparticles’. In this study, the effect of cathode poisoning was investigated as a method to reduce the number of macroparticles in PVD coatings. While the study focuses on the reduction of macroparticles in titanium nitride coatings, the outcomes and key findings can be broadly applied to the cathodic arc process, in particular, for the reduction of macroparticles in more advanced CAE coatings. The results support earlier findings that have shown that poisoning of the cathode can reduce the number of macroparticles emitted from the arc spot. The results of glow discharge optical emission spectroscopy (GD-OES) showed that the titanium content of the coatings varied little between the respective coatings despite changes in the deposition pressure from 0.1 to 1.2 Pa. The GD-OES results also showed the presence of oxide contamination at the surface of the coatings, which was significantly reduced with increasing deposition pressure. The coatings were also deposited onto high-speed steel twist drills to compare the metal-cutting performance when dry drilling a workpiece of cast iron. The results of the drill tests showed that tool life increased with a reduction in the number of macroparticles.

Inverse opal gas sensors : Zn(II)-doped tin dioxide systems for low temperature detection of pollutant gases

Focusing here on the effects of zinc doping in a nanocrystalline matrix of tin dioxide, inverse opal prototype sensors are presented and extensively studied as superior candidates for gas sensing applications. Courtesy of factors including controlled porosity, enhanced surface to volume ratio and homogeneous dispersion of species in the crystalline lattice assured by the sol–gel technique, prototype sensors were prepared with high dopant ratios in a range of new compositions. Exploiting their high sensitivities to low-gas concentrations at low working temperatures, and thanks to the presented templated sol–gel approach, the prepared sensors open up new frontiers in compositional control over the sensing oxide materials, consequently widening the possibilities available in on-demand gas sensor synthesis.

Chemiluminescence from the reaction of tin(II) with tris(2,2'-bipyridyl)ruthenium(III)

Unlike many other metal and metalloid ions, tin(II) elicits intense, analytically useful chemiluminescence upon reaction with tris(2,2΄-bipyridyl)ruthenium(III) in acidic aqueous solution. This finding provides new insight into the nature of this widely used reagent and has enabled the first direct, selective determination of a metal ion with tris(2,2΄-bipyridyl)ruthenium(III).

Air-assisted growth of tin dioxide nanoribbons

SnO₂ nanoribbons have been synthesized by annealing of a milled SnO₂ powder, which is able to evaporate efficiently at the temperature as low as 1100 °C due to the metastable structure created by ball milling treatment. When the milled powder was annealed in an assembly of two combustion boats, SnO₂ nanoribbons formed on the surface of the milled powder. The nanoribbons tend to grow along the [101] crystallographic direction and their side surfaces are represented by ±(010) and ±(101) facets. The oxygen plays an important role in enhancing their formation.

Synthesis of high surface area amorphous tin-zinc oxides by a sol-gel method

A new method to synthesize conducting oxide nanoparticles with low photocatalytic activity was investigated. Initially, the preparation of amorphous ZnO-SnO2 solid solution nanoparticles was studied using a sol-gel technique. It was found that X-ray amorphous nanopowders with low photocatalytic activity were produced when the precipitates were heat treated below 500 °C. However, FT-IR data showed that the sample may not be an oxide semiconductor. A mixture of ZnO and SnO2 crystalline nanoparticles was also produced at 800 °C and found to have much reduced photoactivity than commercial ZnO nanoparticles having a similar specific surface area.