Synthesis and crystal structure of enantiomeric N-(dimethylfluorosilylmethyl) and N-(dimethylchlorosilylmethyl)-[N-(S)-1-phenylethyl)] acetamides

Synthesis of the first optically active compounds containing asymmetric carbon and pentacoordinated silicon has been carried out. The enantiomeric (O-Si)-chelate N-(dimethylhalogenosilylmethyl) acetamides, MeC(O)N(CH(Ph)Me)CH2SiMe2X (X = F, Cl), obtained are the model compounds in studies of the stereodynamic processes at the trigonal-bipyramidal silicon atom and asymmetric induction. An X-ray structural investigation confirmed a 3 + 2 pentacoordination of the Si atom in the title compounds and an axial arrangement of the oxygen and halogen atoms. The geometrical parameters of hypervalent moieties are in good agreement with relations established earlier. (C) 1997 Elsevier Science S.A.