Azasilaboroles I (R = Me, CMe:CH2) were converted in 2 ways to the title compds. (II). I (R = CMe:CH2) was prepd. in several steps from NaBHEt3. The reactions of II with numerous compds., e.g., Me3P, g-picoline and its N-oxide, PCl5, HOAc, and metal complexes such as (MeCN)3Cr(CO)3, were described, and 17O exchange reactions were monitored by 17O NMR. An x-ray anal. of the MeNH2 adduct of II (R = Me) was carried out.