| SYNTHESIS |
The direct synthesis of ARYL-TIN DERIVATIVES by aromatic substitution without the use of expensive & hazardous organometallic compds has been achieved. The team prepd a electrophilic tin(IV) trifluoroacetate material & showed that it reacts reversibly with benzene & p-xylene to make aryl-tin compds. The team synthesized the tin(IV) trifluoroacetate by the reaction of tin(II) oxide with mixt of CF3CO3H & (CF3CO)2O & also by the reaction of Sn(Ph)4 & excess CF3CO2H. The group failed to isolate a well characterized & analytically pure single compd by either method. They therefore call the material trifluoroacetatotin (IV) [(CF3COO)4Sn] & suggest that it may be a complex mixt of compds. The reaction of the material with benzene yielded a organotin cluster contg 4 tin atoms: [(Ph)2(Sn)4(O)2(CF3CO2)10]. The xylyltin compd has similar structure. Co.’s group points out that, in a typical Stille reaction, a aryl or vinyl group of the aryl- pr vinyltributyltin compd, R’Sn(Bu)3, actively participates in the reaction: R-X + R’Sn(Bu)3 = X-Sn(Bu)3 + R-R’ “There are many examples of Stille coupling. “While the reaction is typically stoichiometric in tin reagent, there are descriptions of reactions using tin in catalytic amounts & of using tin reagents with fewer organic groups “Our chemistry only allows us to prepare mono-organotin compds from ‘inorganic’ tin, yet the organotin compds most commonly used in synthesis are tetra-organotin compds” “The discovery in 1998 that suitably activated mono-organotin compds can be used in coupling reactions suggests one possible means whereby our mono-organotin compds could eventually find their way into future synthetic schemes” |
| UPDATE | 10.01 |
| USES |
The team notes that organostannanes have a number of applications, for example in materials used to protect timber against rot; in pharmaceutical screening for antitumor properties & in marine antifouling paints. Tin-based fungicides such as Ph3SnOH are also used in agriculture The researchers add that the major industrial outlet for organotin compds is for the stabilization of PVC against heat & light degradation. They are also used in the catalysis of the reactions between diisocyanates & diols or triols in poly urethane mfg., in transesterifications. Authors point out, however, that there are general environmental concerns about the toxicity & disposal of organostannanes |
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