Diorganotin oxides

Different synthetic routes were developed to prepare distannoxane carboxylates. Two methods commonly used are (i) the reaction of diorganotin oxides with carboxylic acids under azeotropic removal of water and (ii) the hydrolysis of diorganotin dicarboxylates. Diorganotin dicarboxylates are highly moisture-sensitive... 

Fluorodestannylation. Bu4NF is the most reactive source of F, but is difficult to obtain anhydrous. For fluorodestannylation, Harpp and Gingras1 prefer CsF with a catalytic amount of 18-crown-6. This reagent combines with diorganotin oxides, sulfides, or selenides to liberate the corresponding anion, which can be alkylated to give ethers, sulfides, or selenides. 

Diorganotin oxides are the ultimate hydrolysis products of diorganotin halides, and they are generally amorphous solids of unknown structure. 

Diorganotin oxides (R2SnO) generally are polymeric species, which are insoluble in inert solvents bulky compounds, e.g. (t-Bu2SnO)3 and (EtCMe2SnO)3, are trimeric in the solid state with planar Sn303 cores. 

The Sn CP MAS NMR chemical shift of 4 amounts to -232 ppm, which is 53.5 ppm to lower frequency in comparison with the solution chemical shift. We tentatively attribute this to different conformations in the solid state and in solution. To the best of our knowledge 3 and 4 represent the first completely characterized mixed diorganosilicon/diorganotin oxides. 

Functionally substituted metallostannoxanes (M = Si, Ge, Pb, Tl, Hg X = halogen or carboxylate) can also be prepared by reaction between the appropriate metal halide MX and diorganotin oxide R2SnO (e.g. equation 12-31). Little is known about the structures and reactions of these compounds.143... 

The 1,3,2-dioxastannacycloalkanes can be prepared by the usual routes to organotin alkoxides, but whereas simple alcohols react with diorganotin oxides only to the stage of the distannoxanes (R 0)R2Sn0SnR2(0R ), 1,2-diols react further to give the dioxastannolanes (equation 14-41).61 62 The reactions proceed much more quickly (typically in 4 to 9 min) if the reactants are heated in a microwave oven.63 Similar reactions can be carried out with dialkyltin dihalides64 and, under milder conditions, with dialkyltin dialkoxides.65-67... 

The dioxastannolenes are related to the acyclic enolates in the same way as the diox-astannolanes are related to the acyclic alkoxides, and similarly have special properties. They can readily be prepared by reaction of a diorganotin oxide with an acyloin or the cyclic carbonate of an ene-l,2-diol (e.g. equation 14-68).112... 

A distinguishing feature of the stannolenes is their sensitivity to oxygen, and in the air they are oxidised to the 1,2-diones and the telomer of the diorganotin oxide with the stannolene. A radical chain mechanism can be envisaged involving attack of a stannylperoxyl radical at the double bond, analogous to the reaction of acyclic tin enolates with carbon tetrachloride.112... 

Borane is an effective reducing agent for organotin alkoxides and amides,11 and this has been exploited in the preparation of diorganotin dihydrides from the dioxastan-nolanes which can readily be obtained by azeotropic dehydration of a mixture of diorganotin oxide and 1,2-diol (e.g. equation 15-9).12... 

Tetraorganodistannoxane 11 is in equilibrium with cycto-(f-Bu2SnO)3 (14) and the mixed diorganotin oxides cydo-R2Sn(OSnf-Bu2)20, (15, R = Me3SiCH2), and cycto-f-Bu2Sn(OSnR2)20 (16,... 

Figure 2.10.4 Molecular structure of the diorganotin oxide [(MejSiCH2)2SnO]3 (12)...

Scheme 2.10.5 Two pathways proposed to account for the formation of mixed diorganotin oxides 15 and 16...

Figure 2.10.14 Molecular structure of the spacer-bridged diorganotin oxide [ p- R(0)SnCH2SIMe2 2C6H4]3 (R= (Me3SI)2CH)...

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