Investigations on organoantimony compounds VI. Preparation and properties of thermally stable dialkylantimony(v) compounds of the types R2Sb(OR′)3, R2Sb(OAc)3 and R2Sb(O)OH

Abstract

Thermally stable dialkylantimony(V) compounds of the type R2SbX3 (X= OMe, OEt, or OAc) have been prepared in good yields and purity. Hydrolysis of the trialkoxodialkylantimony compounds, R2Sb(OR′)3, results in the quantitative formation of hydroxo(oxo)dialkylantimony compounds, R2Sb(O)OH. These compounds are thermally stable and not sensitive towards oxygen in the air. Therefore, they form suitable starting materials for the synthesis of a variety of dialkylantimony(V) compounds.

Variable-temperature PMR experiments point to the presence of a non-rigid structure for compounds R2SbX3 (R = Me, Et; X = OMe, OAc). At −80° in toluene-d8 dimeric Me2Sb(OMe)3 appears to be rigid within the PMR time scale. The PMR spectrum displays two methoxo group signals in a intensity ratio for the terminal and bridging methoxo groups, respectively. Combined PMR and Raman data indicate a dimeric octahedral structure, in which the methyl groups occupy trans-positions, both in the solid state and in concentrated solutions.

Based on IR and Raman spectroscopic data, a hexacoordinate structure, in which one bidentate and two monodentate acetato ligands occupy equatorial and the two methyl groups occupy axial positions, is proposed for monomeric Me2Sb(OAc)3.