HETEROSILSESQUIOXANES - SYNTHESIS AND CHARACTERIZATION OF GROUP-15 CONTAINING POLYHEDRAL OLIGOSILSESQUIOXANES

The reactions of [(c-C6H11)7Si7O9(OH)3] (1) with PCl3, AsCl3, and SbCl3 give high yields of the corresponding pnictite esters, [(c-C6H11)7Si7O12M], M = P (2), As (3), Sb (4). The bismuth congener, [(c-C6H11)7Si7O12Bi] (5), was prepared by the reaction of 1 with (t-BuO)3Bi. A single-crystal X-ray diffraction study of 2 reveals an interesting molecular structure with 1 of the 12 framework oxygen atoms lying inside the cube defined by the Si and P atoms. Phosphite 2 forms a 1:1 adduct with Me3Al and is quantitatively oxidized to phosphate [(c-C6H11)7Si7O12PO] (7) by ozone.