Organotin compounds dimerization

In 1976, Lappert and co-workers " reported the first stable dialkylstan-nylene (154, Scheme 14.71) in solution. They found that 154 exists as a monomer in the gas phase and as a dimer 153 in the solid state, whereas it exists as a monomer-dimer equilibrium mixture in solution. Extensive studies on the reactions of 154 were carried out, especially on oxidative addition and insertion reactions leading to a variety of new organotin compounds such as 165 and 166 (Scheme... 

Soon after the isolation of 136, Tokitoh et described the synthesis of the first kinetically stabilized diarylstannylene stable in solution, that is, Tbt(Tip)Sn (169), by treatment of TbtLi with stannous chloride followed by addition of TipLi (Scheme 14.74). Under an inert atmosphere, stannylene 169 was found to be quite stable even at 60 °C in solution, and it showed a deep purple color (A,max =561 nm) in hexane. The Sn NMR spectrum of 169 showed only one signal at 2208 ppm, the chemical shift of which is characteristic of a divalent organotin compound as in the case of a monomeric dialkylstannylene (136). The bandwidth and the chemical shift of 169 were almost unchanged between —30 and 60 °C, indicating the absence of a monomer-dimer equilibrium. 

Organoaluminum compounds are used as polymerization catalysts of butene, isoprene and butadiene besides ethylene and propylene, dimerization catalysts of linear higher a-olefins, linear higher-a-alcohols and olefins, productions of organo-metallic compounds such as organotin compounds and organolead compounds, productions of high purity alumina and aluminum thin film. 

Divalent organotin compounds (organostannylenes) represented by R2Sn and the compounds of which R is alkyl or aryl, are liable. But the organic groups shown in eqs. (10.18)-( 10.20) are stably obtained [37—40]. The compound shown in eq. (10.18) has a three-coordination structure of dimer ((Mc3Si)2CH)2Sn-Sn(CH(SiMe3)2)2). On the other hand, the compounds shown in eq. (10.20) is four coordination with the coordination of pyridine. 

The model dimeric H-MA-MMA radicals were generated by reacting the corresponding alkyl bromide (H-MA-MMA-Br) with an organotin compound under irradiation. The ESR spectra were obtained at 30, 60, and 90°C. The spectmm of... 

Syntheses of dialkylthallium halides with bulky alkyl groups such as trimethyl-silylmethyl and neopentyl have been described, these compounds are dimeric. (Acyloxy)arylthallium compoimds have been prepared from organotin compounds, reactions (40), (41). ... 

Compound 87 was the first case found of a stannanethione stable in solution. It was synthesized via the organotin(II) intermediate 71 reaction 11 was followed by UVV spectrophotometry. When the less crowded Ar4 was used instead of substituent Ar1 (see formula 5), the stannathione underwent dimerization to 88199. See also Table 7. 

Few X-ray diffraction data are available for the organotin alkoxides. Trimethyltin methoxide in the crystal is a five-coordinate linear polymer 47,380 and both tin atoms in the methanol solvate, CH2(SnPh2OMe)2-MeOH, are five coordinate, one by intramolecular coordination, and the other by solvation 48.381 Dimethyltin dimethoxide 49,382 dimethyltin diphenoxide 50,383 and isopropyltin triisopropoxide 51384 are five-coordinate oxygen-bridged dimers. All these compounds are monomers in solution. 

In the condensed phase Me3SiF molecules show no intermolecular interactions, while the same germanium derivatives are associated as a dimer due to intermolecular F Ge coordination. According to the tendency for tetrahedral main-group 14 elements to expand the coordination sphere, organotin fluorides show a strong tendency to associate in the solid state and even in triorganotin fluorides the tin atom is five-coordinate A common feature of this class of compounds in the solid state is coordination expansion of the tin atom due to hypervalent interaction, which in turn often results in formation of polymeric materials. 

Some organotin carboxylates have structures totally different from those just discussed. For example, Bu2Sn(OOC6H4Br-2)2 is a weakly bridged dimer [497], whereas di-u-butyltin cyclobutane-dicarboxylate, Bu 2Sn(OOC)2C4H6, forms a zigzag polymer [498]. In both compounds tin is six-coordinate octahedral. 

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