FORMATION OF ORGANOSILICON COMPOUNDS .3. THE HYDROGENATION OF SI-CHLORINATED, C-SPIRO-LINKED 2,4-DISILACYCLOBUTANES WITH LIALH4 OR IBU2ALH - THE ACCESS TO SI8C3H20

The hydrogenation of Si-chlorinated, C-spiro-linked 2,4-disilacyclobut anes containing C(SiCl3)2 terminal groups with LiAlH4 in Et2O proceeds under complete cleavage of the fourmembered rings and under eliminati on of one SiH3 group. Such, Si8C3Cl20 4 forms (H3Si)2CH-SiH2-CH(SiH3)- SiH2-CH(SiH3)2 4a, and even Si8C3H20 4a with LiAlH, forms 4a. The hydr ogenation of related compounds containing however CH(SiCl3) terminal g roups similarly proceeds under ring cleavage but no SiH3 groups are el iminated. Such, (Cl3Si)CH(SiCl2)2CH(SiCl3) 41 forms (H3Si)2CH-SiH2-CH2 (SiH3) 41 a. However, in reactions with iBu2AlH in pentane neither the disilacyclobutane rings are cleaved nor are SiH, groups eliminated. O nly by this method Si8C3H20 is accessible from 4, Si6C2H16 3a from Si6 C2Cl16 3 and Si4C2H12 41a from 41. C(SiCl3)4 cleanly produces C(SiH3)4 . Based on the knowledge about the different properties of LiAlH4 and iBu2AlH in hydrogenation reactions of disilacyclobutanes it was possib le to elucidate the composition and the structures of the hydrogenated derivatives of the product mixture from the reaction of MeCl2Si-CC12- SiCl3 with Si(Cu) [1] and to trace them back to the initially formed S i chlorinated disilacyclobutanes Si6C2Cl15Me 34, Si6C2Cl14Me2 35, Si8C 3Cl19Me 36 and Si8C3Cl18Me2 37. Compound 4a forms colourless crystals of space group P1BAR with a = 799.7(6), b = 1 263.6(12), c = 1758.7(14 ) pm, alpha = 103.33(7)-degrees, beta = 95.28(6)-degrees, gamma = 105. 57(7)-degrees and Z = 4.