Silicon organotin compounds

In silicones, organotin compounds are used for the formulation of RTV silicone elastomers. These are reactions of silicones... 

Another major use of organotin compounds is as curing agents for the room temperature vulcanization of silicones the 3 most commonly used compounds are Bu2SnX2, where X is acetate, 2-ethylhexanoate or laurate. The same compounds are also used to catalyse the addition of alcohols to isocyanates to produce polyurethanes. 

This technique has been applied to the determination of arsenic, selenium, organocompounds of arsenic, mercury and tin in soils, carbohydrates, total sulphur, arsenic, antimony, bismuth, selenium and organocompounds of mercury, tin and silicon in non-saline sediments, arsenic, bismuth, selenium or organotin compounds in saline sediments and arsenic and selenium in sludges. 

Organotin compounds have various industrial uses. Disubstituted organotins are used in the production of plastics including food wrap where they act as stabilizers at 0.5%-2.0% by weight (WHO 1980). Disubstituted organotins are added to polyurethane foams and silicone to increase their strength and to minimize stickiness and odors (WHO 1980). 

Organylstannantriols RSn(OH)3 have not yet been isolated. Consequently, organotin compounds R2Sn(OH)2 and RSn(OH)3 are less stable than their isostructural compounds of silicon and germanium, which in turn are not highly stable. However, their formation as intermediate compounds in hydrolysis reactions of R2S11X2 and RSnX3 seems likely. 

In contrast to the extensively studied doubly bonded systems of silicon and germanium, the chemistry of the corresponding tin compounds, i.e. distannenes and stannenes, has not been fully disclosed yet probably due to the much higher reactivity and instability of such low-coordinated organotin compounds. In the following sections we briefly describe the synthesis and properties of stable distannenes and stannenes. 

The majority of the more important methods for the preparation of fluorinated compounds by substitution reactions have been reviewed in the previous sections. There are, however, some additional important synthetic procedures which should also be mentioned, mainly those concerned with the introduction of fluorine by substitution of functional groups containing boron, silicon and tin the reactions of organotin compounds are the most well-studied to date. These reactions are excellent synthetic methods for obtaining vinyl and aryl fluorides (sec also Section 1.1.1.1.). 

The reaction is of practical importance in the vulcanization of silicone mbbers (see Rubbercompounding). Linear hydroxy-terminated polydimethylsiloxanes are conveniently cross-linked by reaction with methyldiethoxysilane or triethoxysilane [998-30-1]. Catalysts are amines, carboxylic acid salts of divalent metals such as Zn, Sn, Pb, Fe, Ba, and Ca, and organotin compounds. Hydroxy-terminated polysiloxanes react with Si—H-containing polysiloxanes to... 

Figure 2.17. Electron spectroscopy for chemical analysis ESCA) spectra of organometallic polymer films before and after exposure to oxygen plasma. The silicon 2p transition page 99) is shifted from 99.7 to 102.4 eV. The magnitude of the shift is consistent uMh conversion to SiO, where x is between 1.5 and 2. The Sn 3d transitions of the organotin compound above) undergo a similar shift 1.7 eV), consistent with generation of a SnOx surface, where x is again between 1.5 and 2. Argon sputter etching followed by ESCA analysis indicates that these oxide films are less than 100 A thick.

In parallel with these developments, organotin compounds have found a variety of applications in industry, agriculture, and medicine, though in recent years these have been circumscribed by environmental considerations. In industry they are used for the stabilization of poly(vinyl chloride), the catalysis of the formation of the polyurethanes, and the cold vulcanisation of silicone polymers, and also as transesterification catalysts. 

Ferrier RJ (2001) Direct Conversion of 5,6-Unsaturated Hexopyranosyl Compounds to Functionalized Glycohexanones. 215 277-291 Frey H, Schlenk C (2000) Silicon-Based Dendrimers. 210 69-129 Fugami K, Kosugi M (2002) Organotin Compounds. 219 87-130 Fuhrhop J-H,see Li G (2002) 218 133-158... 

A tin hydride attached to fluorous ponytails is quite versatile in respect of easy separation of the desired products from organotin compounds. When an iodoalkene was treated with NaCNBHs in the presence of a catalytic amount of fluor-oalkyltin hydride, the desired tricyclic ketones were produced (Scheme 12.133) [240]. Application of the crude mixture to a small plug of fluorous reversed-phase silica gel enabled facile separation of the cyclic ketone obtained (fluorous solid-phase extraction, FSPE). In contrast, when tris(trimethylsilyl)silane (TTMSH) was employed as a hydride source chromatographic purification of the nonpolar and somewhat volatile products was impossible because of contamination by nonpolar silicon-containing byproducts. 

The relative reactivities of organometallics containing group 14 elements are closely associated with the electronegativity and dissociation energy of the M—C bonds of the elements. For example, some organotin compounds such as allylstannanes are easily decomposed to form radical species whereas homolysis of the carbon-silicon bond of allylsilanes is rarely achieved, which reflects the dissociation energy of the respective M—C bonds. 

C. J. Evans and S. Karpel. Organotin Compounds in Modem Technology, Journal of Organometallic Chemistry Library, 16 Elsevier, Amsterdam, 1985, 280 pp. S. J. Blunden, P. a. Cusack and R. Hill, The Irulustrial Uses of Tin Chemicals, Royal Society of Chemistry, London, 1985, 346 pp. K. Das, S. W. Nc and M. Gielen, Chemistry and Technology of Silicon and Tin, Oxford University Press, Oxford, 1992, 608 pp. 

Organo-compounds of the group 14 elements include some important commercial products, and we have already discussed silicones in Section 13.10 and Box 13.12. Organotin compounds are employed as polyvinylchloride (PVC) stabilizers (against degradation by light and heat), antifouling paints on ships, wood preservatives and... 

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