Dibutyltin dialkoxides

The changes in chemical shift as a function of concentration and temperature for the dibutyltin dialkoxides (63) are shown in Fig. 6. 

Holecek et al. have measured 13C NMR data for a wide range of dibutyltin(IV) compounds.46 Chemical shifts for C-l to C-4 of butyl groups in simple dibutyltin dialkoxides have values of about 19, 27, 26, and 13 ppm, respectively.46 The chemical shifts of the C-l carbons are somewhat dependent on the nature of the compound and its state of association. For 2,2-dibutyl-l,3,2-dioxastannane, the chemical shift of the butyl C-l was about 20 ppm when the attached tin atom was pentacoordinate, but about 27 ppm when it was hexacoordinate.42... 

In solution, the dibutyltin dialkoxides and alkyltin trialkoxides are dimeric unless the alkoxyl groups are bulky, and the enthalpy of dissociation of the dialkoxide dimers is 60-100 kJ mol C3 25 Dimethyltin dimethoxide shows a sharp 119Sn NMR signal in solution at 8 -162, consistent with five-coordinate tin, and in the crystal it has the structure 14-2.26 Dimethyltin diphenoxide similarly is an oxygen-bridged dimer in the crystal, and in solution is in equilibrium with the monomer.27... 

It has also been found that p-toluenesulfonation reactions can be conducted with catalytic dibutyltin oxide if a stoichiometric amount of base, normally triethylamine, is present. These conditions can also be used for acylation of l-phenyl-l,2-ethanediol with dibutyltin dialkoxides as catalysts and is also effective in the acylation of glycerophosphoryl choline, but only when 2-propanol is the solvent (Scheme 5.1.3). ... 

Monotin alkoxides, tin dialkoxides and cyclic tin alkoxides have been utilized as initiators in the ROP of cyclic esters. The tin alkoxides are known to form cyclic species during synthesis and the dibutyltin alkoxides are known to exist as monomers and dimers [74]. The cyclic tin alkoxides were originally studied because of their resistance towards hydrolysis [75]. The tin alkoxides have been reported to be effective transesterification catalysts initiating polymerization at moderate temperatures [76]. 

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