ORGANOSUBSTITUTED 1,2-DIHYDRO-1,2,5-DISILABOREPINES

1,2-Di-1-propynyl-tetramethyldisilane (1) reacts with triorganoboranes R3B [R = Et (2a), CH2Ph (2b), Ph (2c), 2-thienyl (2d)], 9-ethyl-9-bor abicyclo[3.3.1]nonane (3), and diethyl(N-pyrrolyl)borane (4) by twofol d 1,1-organoboration to give selectively the respective organo-substit uted 1,2-dihydro-1,2,5-disilaborepines 5a-d, 6, and 7 in high yields. The compounds 5-7 were characterized by H-1-, B-11-, C-13-, and Si-29- NMR spectroscopy in solution. The molecular structures of the disilane 1 and of the heterocycle 5c were determined by X-ray structure analys is.