| Abstract: | Formation of Organosilicon Compounds. 108 [1]. Thermally Induced Reactions of Amino-Substituted Disilanes Thermally induced reactions of amino-substituted disilanes yield Si rich silanes. At 300°C, Me3Si? SiMe2? NMeH 1 yields Me3Si? NMeH 2 and Me3Si? (SiMe2)2-NMeH 3 in a ratio 1 : 2 : 3 = 1,6 : 1 : 1, whereas Me3Si? SiMe2? N(iPr)H 4 at 350°C yields Me3Si? N(iPr)H 5 , Me3Si? (SiMe2)2-N(iPr)H 6 and Me3Si? (SiMe2)3? N(iPr)H 7 in a ratio of 4 : 6 : 7 = 0.8 : 1.0 : 0.6. Me3Si? SiMe2? NMe2 8 at 300°C (72 h) yields Me3Si? NMe2 9 and Me3Si-(SiMe2)2-NMe2 10 in a ratio of 9 : 8 : 10 = 1 : 0.22 : 0.44 The thermal stability of these disilanes is determined by the sterical requirements of the amino substituents NMeH < NMe2 < N(iPr)H. The introduction of a second NMe2 group decreases the stability and favours the formation of Si rich silanes. Such, Me2N? (SiMe2)2? NMe2 11 already at 250°C (2 h) yields Me2N? SiMe2? NMe2 12 , Me2N? (SiMe2)2? NMe2 13 and Me2N? (SiMe2)4? NMe2 14 in a ratio of 11 : 13 : 14 = 0.3 : 0.9 : 1.0. The reactions can be understood as insertions of thermally produced dimethylsilylene into the Si? N bond of the disilanes. This process is strongly favoured as compared to the trapping reactions with Ph? C?C? Ph or Et3SiH. The mentioned reactions correspond closely to those of the methoxy-disilanes[2]. However (MeN? SiMe2? SiMe2)2 15 , obtained from HMeN? (SiMe2)2? NMeH by condensation [3], at 400°C suffers a ring contraction to octymethyl-1,3-diaza-2,4,5-trisilacyclopentane (69 weight %), and yields also some solid residue, the composition of which corresponds to Si3C7NH21. |
