Stereochemical studies of the addition of hydrogen halides and water to the <i>Z</i> and <i>E</i> isomers of a disilene

The stereochemistry of the addition of H X ( X = Cl, Br, I, and OH) to the Z and E isomers of 1,2-di- tert-butyl-1,2-bis(2,4,6-triisopropylphenyl)disilene (9 Z or 9 E ) is 100% stereospecific. Anti addition of HCl to 9 Z or 9 E gives the chlorodisilane 10a, ( S,R/R,S)-10a, and ( S,S/R,R)-10a, respectively, whereas syn addition of HBr or HI results in the formation of bromodisilane 10b and the iododisilane 10c, ( S,S/R,R)-10b/c, and ( S,R/R,S)-10b/c, respectively. Likewise, stereospecific syn addition of H 2 O to 9 Z or 9 E gives the disilanols 10d, ( S,R/R,S)-10d, and ( S,S/R,R)-10d, respectively. Hydrolysis of the halodisilanes 10a-c occurs with inversion of configuration at the stereogenic silicon centre. Hydrolysis of the related aminodisilane requires acid catalysis and also occurs with inversion of configuration at the silicon centre.