Dimerization organotin

The structural chemistry of some metal dithiocarbamates, i.e. systematics, coordination modes, crystal packing, and supramolecular self-assembly patterns of nickel, zinc, cadmium, mercury,363 organotin,364 and tellurium,365 366 complexes has been thoroughly analyzed and discussed in detail. Supramolecular self-assembly frequently occurs in non-transition heavier soft metal dithiocarbamates. Thus, lead(II),367 bismuth(III)368 zinc,369 cadmium,370 and (organo)mercury371 dithiocarbamates are associated through M- S secondary bonds, to form either dimeric supermolecules or chain-like supramolecular arrays. The arsenic(III)372 and antimony(III)373 dithiocarbamates are... 

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 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. 

The reaction of isoprene with C02 in the presence of organotin ethoxide and DBU by the use of dicyclohexyl(/3-pyridylethyl)phosphine (106) affords the isomeric esters 107 and 108 by head-to-tail and tail-to-tail dimerizations. Tin ethoxide forms tin carbonate, which seems to be an effective carrier of C0 [100],... 

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. 

The reaction of butyltin trichloride with l-(2-methyl-2,3-dihydrobenzotriazol-2-yl)-propan-2-one gives an organotin complex that was formulated as containing the [BuSn(OH)Cl3]2 anion " . However, a reinvestigation of the crystal structure of this complex reveals a neutral hydroxyl-bridged aqua-butyldichlorotin hydroxide dimer that is linked to four 2-methylbenzothiazole molecules by short hydrogen bonds " . 

Such a dimer has also been observed containing bridged organotins. Indeed, the hydrolysis of 1,3-bis(trichlorostannyl)propane, in water, yields a solid where the dimers are associated by the alkyl spacer in infinite chains. ... 

Concerning the oxygen-containing bidentate ligands [R E02+ ] and MC, discrete dimeric, tetrameric and hexameric ring assemblies have been reported for organotin carboxylate, phosphinate, phosphonate monoester, phosphate diester, " sulfonate, and tungstate derivatives. 

Figure 2.5.6 Examples of (a) dimeric (b) tetrameric (c) hexameric and organotin assemblies bridged by inorganic oxygen-containing connectors...

Dicarboxylates or carboxylates containing an additional anionic function (e.g. RS , RO, etc.) capable of coordination to tin atoms (functionalized monocarboxylates) are ideal candidates for the constmction of discrete di- and oligonuclear organotin macrocycles, as is shown by a series of organotin carboxylate macrocycles having dimeric, trimeric, tetrameric, and hexameric compositions (Figure 2.5.11). 

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