Alkyltins

Alkylphenols Alkyl polyglycosides N-Alkylpyrroles Alkyl thiophenes Alkyltins Alkynes... 

Alkyltin Intermedia.tes, For the most part, organotin stabilizers are produced commercially from the respective alkyl tin chloride intermediates. There are several processes used to manufacture these intermediates. The desired ratio of monoalkyl tin trichloride to dialkyltin dichloride is generally achieved by a redistribution reaction involving a second-step reaction with stannic chloride (tin(IV) chloride). By far, the most easily synthesized alkyltin chloride intermediates are the methyltin chlorides because methyl chloride reacts directiy with tin metal in the presence of a catalyst to form dimethyl tin dichloride cleanly in high yields (21). Coaddition of stannic chloride to the reactor leads directiy to almost any desired mixture of mono- and dimethyl tin chloride intermediates ... 

The other commercially important routes to alkyltin chloride intermediates utilize an indirect method having a tetraalkjitin intermediate. Tetraalkyltins are made by transmetaHation of stannic chloride with a metal alkyl where the metal is typicaHy magnesium or aluminum. Subsequent redistribution reactions with additional stannic chloride yield the desired mixture of monoalkyl tin trichloride and dialkyltin dichloride. Both / -butjitin and / -octjitin intermediates are manufactured by one of these schemes. 

Stabilizer Synthesis. The selected alkyltin chloiide intermediate reacts with either a carboxyhc acid or a mercaptan in the presence of an appropriate base, such as sodium hydroxide, to yield the alkyltin carboxylate or alkyltin mercaptide heat stabihzet. Alternatively, the alkyltin chloride can react with the base to yield the alkyltin oxide, which may or may not be isolated, for subsequent condensation with the selected carboxyhc acid or mercaptan. 

Table 2. U.S. Producers and Trade Names of Alkyltin Stabilizers and Mixed Metal Stabilizers ...

Producers Alkyltin trade names Mixed metal trade names... 

Table 3. Typical Uses And Prices For Alkyltin Stabilizers...

Particular drawbacks of using alkylsiHcon and alkyltin haHdes with AlCl for the cationic polymerization of terpenes are low yields and the fact that they require rigorously dried feeds (<50 ppm H2O) to be effective. Increased water content results in lower yields and lower softening points (85). Catalyst systems comprised of AlCl with antimony haHdes in the presence or absence of a lower alkyl, alkenyl, or aralkyl haHde are particularly effective in systems containing up to 300 ppm H2O (89,90). Use of 2—12 wt % of a system composed of 2—3 parts AlCl, 0.7—0.9 parts SbCl, and 0—0.2 parts of an organic... 

Allylstannanes are also available from allyl sulfoncs24 and sulfides25 by treatment with tri-alkyltin hydrides under free-radical conditions. Of some interest is the stereocontrol exercised by a neighboring hydroxy group, possibly because of interaction with the tin26. 

Acidolysis of the alkyl-tin bond provides a useful route from tetraal-kyltins to alkyltin carboxylates, and is discussed in Section II,C. 

With functionally substituted, alkyltin compounds, the functional substituent may become involved in the cleavage process, resulting in an intramolecular reaction, e.g.. 

The reactions of tetraorganotins with ICl, EBr, and CICN have been investigated as synthetic routes to aryl cyanides (111) and alkyltin bromides and chlorides (112,113). 

Whereas bromine radicals (133) and succinimidyl radicals (134) react by the Sh2 mechanism at the tin center in tetraalkyltins, but not in alkyltin halides, alkoxyl radicals (135) and ketone triplets (136) react with alkyltin halides, but not tetraalkyltins this may reflect the conflicting, electronic demands of the radical reagents which, as electrophilic species, should be more reactive towards tetraalkyltins than alkyltin halides, but which would also tend to make use of a 5d orbital... 

The relative reactivities of alkyltin compounds towards tert-butoxyl radicals, ketone triplets, and succinimidyl radicals are dominated by the steric effect of the alkyl ligands (R" > R"), but that towards bromine atoms follows the reverse sequence (R" < R ). 

Tin-tin bonds are usually best prepared by reducing an Sn-0 or Sn-N bonded compound with a tin hydride. For example, trimethyl (diethylamino)tin is reduced by alkyltin trihydrides to give decaorganotetratins (256). 

As discussed in section 2, the alkyltin component of organotin compounds is relatively stable to environmental degradation processes such as hydrolysis, compared with the association with the relative ligand (such as an isooctyl mercaptoacetate group). Thus, in water, most of the derivatives are reported to dissociate to the constituent alkyltin (usually as the chloride or the oxide) and the relevant anion (KemI, 2000). 

Antitumour activity has been reported for alkyltins, particularly dibutyltin. The effect in mouse skin initiation/promotion protocols showed dibutyltin inhibiting the promotion stage (Arakawa Wada,... 

Arakawa Y, Wada O (1993) Biological properties of alkyltin compounds. In Sigel H, Sigel A, eds. Metal ions in biologioal systems. Vol. 9. New York, NY, Marcel Dekker, pp. 101-136. 

Boeri RL, Kowalski PL, Ward TJ (1995) Acute toxicity of the water accommodated fraotion (WAF) of alkyltin MAto the sheepshead minnow, Cyprinodon variegatus. T.R. Wilbury Laboratories, Ino., Marblehead, MA, 10 November (Study No. 863-MO). 

Penninks AH, Seinen W (1982) Comparative toxicity of alkyltin and estertin stabilizers. Food and Chemical Toxicology, 20 909-916. 

The rate of dissolution of PTF and BTF in nonpolar solvents is considerably higher than in tri-n-alkyltin fluorides. The former dissolve instantly while the latter dissolve only by a slow swelling process. This indicated that the presence of the trimethylsilyl group, at the end of the chain and somewhat away from... 

The concentration at which a steep rise in this curve begins has been termed as the critical or threshold concentration (2,3). Figure 6 shows such typical curves for PTF and BTF in n-hexane. Despite the fact that different shear rates are involved in capillary viscometry, it can be qualitatively said that at a given concentration, PTF viscosified n-hexane better than BTF. It is clear from Figure 6 that the critical concentration for these two compounds is above 0.7%, while analogous tri-n-alkyltin fluorides showed a critical concentration of less than 0.4% (3). This may be due to the presence of bulky Me3Si-groups nearer to the Sn-F bond, which causes some steric hindrance to auto-association. 

Mixed alkyltin hydrides are relatively difficult to prepare. Nevertheless, a convenient synthesis starts from the reaction of SnBr4 or SnLt with 2,4,6-tri-f -butylphenyllithium 105 ... 

Alkylhalotin hydrides are prepared by reaction of an alkyltin hydride with either an alkyltin halide with the same alkyl groups232 or with hydrogen halides233, e.g. ... 

SnCl2 reacts with triphenylethenyllithium Li(CPh=CPh2) in Et20-w-hexane-THF to yield an alkenyltin(II) derivative which, subsequently treated with butyl bromide, yields a mixed alkyltin halide362 ... 

Alkyltin trihalides with chain lengths of up to 18 carbon atoms can be prepared in the presence of trialkylantimony catalysts340 ... 

Redistribution reactions are considered as quite important for the preparation of alkyltin halides having mainly identical alkyl groups. Actually, the redistribution reactions are halogenation reactions of organotin halides by SnX4 (X = F, Cl, Br, I). 

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