DIFFERENCES IN REACTIVITY OF 1,4-DISILABUTANE AND NORMAL-TETRASILANE TOWARDS SECONDARY-AMINES

1,4-Disilabutane H3SiCH2CH2SiH3 (1) and n-tetrasilane H3SiSiH2SiH2SiH3 were employed as model systems for the preparation of silicon-rich aminosilanes potentially useful for the deposition of silicon nitride Si3N4. 1 reacts with the appropriate equivalents of diethylamine in an alkane solvent and in the presence of the two-phase catalyst NaNH2/18-crown-6 to give the products (Et2N)2SiHCH2CH2SiH3, (Et2N)2SiHCH2CH2SiH2(NEt2), and (Et2N)2SiHCH2CH2SiH(NEt2)2. By contrast, n-Si4H10 undergoes a cleavage reaction under similar conditions to yield H3SiNEt2 and H2Si(NEt2)2 together with a mixture of polysilanes Si(n)H2n+2, the composition of which is depending on the reaction conditions and the nature of the catalyst (NaH and NaNH2). Diethylaminopolysilanes are also formed, but only in trace quantities. Treatment of n-Si4H10 with pyrrole (C4H5N) leads to the formation of trisilane accompanied by the pyrrolylsilanes H2Si(C4H4N)2, HSi(C4H4N)3, and Si(C4H4N)4. The differences in reactivity suggest excellent leaving group properties of silyl anions in the reaction with amines.