Synthesis, functionalization and properties of incompletely condensed half cube silsesquioxanes as a potential route to nanoscale Janus particles

Article abstract of DOI:10.1016/j.crci.2009.10.007

Multiple literature reports describe the synthesis of [RSiO(OH)]₄ or [RSiO(ONa)]₄ compounds. Surprisingly, in the majority of cases the OH or ONa groups all lie on the same face of the cyclomers or half cubes. Consequently, it appears possible to couple R containing half cubes with R' containing half cubes to form bi-functional (Janus) silsesquioxane cages or cubes. We report here synthesis of [PhSiO(ONa)]₄ and [p-IPhSiO(ONa)]₄ half cubes. We thereafter discuss efforts to react the [PhSiO(ONa)]₄ salt with (R = Me, vinyl, and cyclohexyl) RSiCl3 in MeOH to produce the compounds {PhSiO[OSi(OMe)2R]}₄ species which were characterized using traditional spectroscopic procedures. These compounds were then subjected to acid catalyzed hydrolysis tohydrolytically remove the OMe groups to generate Janus cubes. While it is possible to isolate the target compounds, which were also characterized in detail, the yields were lower than expected perhaps because of competitive hydrolytic cleavage of the Si-O-SiR(OMe)₂ linkage.