Bildung Siliciumorganischer Verbindungen. 103. Bildung und Struktur von cis- und trans-2,4-Dichloro-2,4-bis(trimethyl-silyl)-1,1,3,3-tetramethyl-1,3-disilacyclobutan

Formation of Organosilicon Compounds. 103. Formation and Structure of cis and trans 2,4-Dichloro-2,4-bis(trimethylsilyl)-1,1,3,3-tetramethyl-1,3-disilacyclobutane The reaction of Me₃Si? CCl₂? SiMe₂Cl with LiBu in THF yields 1,1,3,3-Tetramethyl-2,4-bis(trimethylsilyl) 1,3-disilabicyclo1.1.0]butane. The product of the first reaction stage is Me₃Si? CCl(Li)-SiMe₂Cl. The 1,3-Disilacyclobutane 2 and 3 were isolated, when Me₃Si? CCl₂? SiMe₂Cl was treated with LiBu in Et₂O. This way the proof is given that 2 and 3 are intermediates of the formation of product 1 . The further products are 4 and 5 (CCl in 2 and 3 substituted by CH) and Me₃Si? CH₂? C(SiMeCl)₂SiMe₃. 2 crystallizes orthorhombically in the space group Fdd 2 (no. 43) with a = 2149.1 pm, b = 2229.2 pm, c = 1763.6 pm and Z = 16 molecules per cell. The central ring of disilacyclobutane is slightly folded (17.9°). The configuration of the C-Atoms in this four membered ring gets closer to a sp² configuration built up by three Si? C bonds. The Cl-atoms approximately have orthogonal positions to these CSi₃ arrangements. The extension of the C? Cl bonds (184.6 pm) and the mutual approximations of the Cl-atoms in the cis-position indicate a high reactivity of the molecule.