Polyhedral antimony(III) and bismuth(III) siloxanes: Synthesis, spectral studies, and structural characterization of [Sb(O3SiR)]4 and [Bi12(O3SiR)8(μ3-O)4Cl4(THF)8] (R = (2,6-iPr2C6H3)N(SiMe3))

The antimony(III) and bismuth(III) containing siloxanes [Sb(O3SiR)]4 (2) and [Bi12(O3SiR)8(μ3-O)4Cl4(THF)8] (3) (R = (2,6-iPr2C6H3)N(SiMe3)) have been prepared by the reaction of lipophilic N-bonded silanetriol 1 with the corresponding metal amides M(NMe2)3 (M = Sb, Bi). The composition and molecular structures of 2 and 3 have been fully determined by mass spectrometry, IR, NMR spectroscopy, elemental analysis, and lower temperature X-ray crystal structural analyses. Compound 2 represents the first example of a structurally characterized cubic antimony(III) containing siloxane ligands, whereas compound 3 exhibits a new highly soluble bismuth(III) cluster containing chloride and siloxane ligands. Hydrophobic groups, surrounding the central Si4O12Sb4 and Bi12Cl4O28Si8 cores, play an important role in the high solubility of compounds 2 and 3 in common organic solvents. Several attempts to assemble the analogous bismuth(III) containing chloride free siloxane cluster were not successful. In our hands only the chlorine containing cluster resulted in the formation of single crystals.