Tin alkylation

In contrast to the scarcity of stable poly(pyrazolyl)borato alkyl complexes of Si, Ge, and Pb, such derivatives are common for tin. The first poly(pyrazolyl)borato tin alkyl derivatives to be prepared were the parent derivatives, namely five-coordinate [Bp]SnMe Cl3 and six-coordinate [Tp]SnMe Cl3 (n = 0-3), obtained by the reactions of MenSnCl4 with K[Bp] and K[Tp], respectively [Eqs. (25) and (26)] (116). 

In addition to tin alkyl derivatives with one poly(pyrazolyl)borato ligand, bis[(poIy)pyrazolylborato] complexes of the types [Tp]2SnR2 and [R2Bp]2SnR2 have also been prepared (123,124). 

Tin alkyl hydrides can be prepared from the halides by the reaction with lithium aluminum hydride. 

D.R. McMillin, Purdue University You have suggested that certain oxidants are more sensitive to steric effects when reacting with the tin alkyls. Is there evidence for preferential attack of the less bulky alkyls when unsymmetrical reagents such as SnR2R2 or SnR3R are used ... 

Our first example that attempts to imravel this complexity is entitled Gas-Phase Thermochemistry and Mechanism of Organometallic Tin Oxide CVD Precursors . The authors, M. Allendorf and A.M.B. van Mol, describe the development of quantum chemistry methods that can predict heats of formation for a broad range of tin compounds in the gas phase, which need to be considered when Sn(CH3)4 or (CH3)2SnCl2 and other tin alkyls are used as precursors together with oxygen and water for tin oxide deposition. 

Tin alkyls can also be made from the reaction of SnCL with aluminum alkyls, highly reactive, oxygen-sensitive materials which are obtained industrially from olefins, hydrogen, and aluminum powder ... 

In this series of experiments the reactivity of hydrogen chemisorbed on granular skeletal nickel catalyst towards different tin alkyl compounds, i.e. SnEt, SnBu, SnEt Cl and SnBz2Cl2 [Et =... 

It has been demonstrated that skeletal nickel catalysts can be modified with tin by using CSRs taking place between tin alkyls and hydrogen adsorbed on nickel. Upon applying this type of modification the selectivity pattern of the catalysts in the reductive ami-nation of acetone can be tailored. Selective poisoning of sites responsible for the formation of isopropanol could be achieved by using tin dibenzyl (or diethyl] dichloride as tin precursor compound. ... 

The reaction between powdered tin, hydrogen chloride, and an a,/3-nnsatnrated carbonyl or cyano compound produces diorganotin dichloride species (equation 3). Tin(II) halides react similarly to give X3SnCH2CH2Y (equation 4). Direct reactions of tin(II) halides with alkyl halides to give aUcyltin trihalides require the same catalysts as used for tin/alkyl halide reactions trialkylstibines are particularly effective catalysts (equation 5). 

Table XIII. of the Appendix gives a list of compounds prepared by the following general method, together with their physical constants, Three times the ealeulated quantity of magnesium alkyl halide is used, and after the introduction of the tin alkyl halides the mixture is boiled under reilux for two hours, the etlier removed, and the residue baked on the water-buth lor one liour. After cooling, ether is added, and the whole deosed with water. Mixed tin tetra-alkyls are converted into inixed tin trialkyl bromides of the type R R SnX by the action of bromine at - 40° to —30° C., ati alkyl group being split out, this resembling the bromination of lead alkyls.

A collection of physical data of various tin alkyls is shown in Table XVI- of the Appendix. ... 

Tin trimethyI-5-bromoamyl, prepared in the usual way, is a colourless, thin, air-stable oil, having an odour resembling the tin alkyls. 

TABLE XIV.—PHYSICAL CONSTANTS OF TIN ALKYLS OF THE TYPE RgSnR a. 

The S-sulfinate or 1,1-insertion product, reviewed in 11.3.2.3, is the most common. These products are characterizedby vs-o of 1100-1250 and 1000-1100cm in the IR spectrum. Other isomers have two vs-o absorptions below 1085 cm The 1,2-insertion products, 0-sulfinites, are the initial species generated on SO2 insertion even when the product is an S-sulfinate. For oxophilic metals this product may be stable. Insertion into Sb-Ph and Ti-Ph bonds have been claimed to yield 0-sulfinates and tin alkyls, [reaction (i)], as have zinc alkyls . 

Upon increasing the amount of tin (Sn/Rhs=0.8) both adatoms and alkyl-tin fragments are present on the surface. The selectivity of the desired product remains close to 90%, but the rate of the reaction is drastically decreased. More sites have been blocked by tin adatoms or tin alkyl fragments. 

Use of substituted diazoalkanes, such as ethyl diazoacetate, leads to functional tin alkyls. The potential applications in preparing interesting alkyl-boranes from boron hydrides should be apparent. 

The applications of organometallic agents in technology show every promise of increasing. The traditional use of tetraethyllead in motor fuels may eventurlly be replaced by some other type. Tin alkyls have gained some recent prominence both for the biocidal properties of certain trialkyl-tin derivatives and for the ultraviolet-discoloration protection offered vinyl plastics by dibutyltin dilaurate. Also attention should be drawn to the possi-... 

Tin oxide films have been deposited onto soda-lime-silica glasses in a cold-wall reactor at substrate temperatures between 350°C and 490°C [108]. The mechanism of formation was carefully studied using four different tin alkyls as starting compounds namely dibutyl tin diacetate (DTD), tetrabutyl tin (TBT), tetraethyl tin (TET) and tetramethyl tin (TMT). The investigations showed for the mechanism a dependence on the molecular structure and reactivity of the initial tin compound to oxygen. The influence of substrate temperature on deposition rate (Arrhenius plots) showed three characteristic regions for which three processes were proposed [108] ... 

Tin films can be deposited by pyrolysis of tin alkyls or alkyl hydrides such as ... 

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