Synthesis and Properties of Branched Hydrogenated Nonasilanes and Decasilanes

Branched higher silicon hydrides Si n H2n+2 with n > 6 were recently found to be excellent precursors for the liquid phase deposition of silicon films. Herein we report the gram-scale synthesis of the novel nona- and decasilanes (H3Si)3Si­(SiH2) n Si­(SiH3)3 (2: n = 1, 5: n = 2) from (H3Si)3SiLi and Cl­(SiPh2) n Cl by a combined salt elimination/dephenylation/hydrogenation approach. Structure elucidation of the target molecules was performed by NMR spectroscopy and X-ray crystallography. 2 and 5 are nonpyrophoric and exhibit a bathochromically shifted UV absorption compared to neopentasilane and the structurally related octasilane (H3Si)3SiSi­(SiH3)3. TG–MS analysis elucidated increased decomposition temperatures and decreased ceramic yields for branched hydrosilanes relative to cyclopentasilane. Otherwise, very similar thermal properties were observed for hydrosilane oligomers with linear and branched structures.