Synthesis and Properties of Branched Hydrogenated Nonasilanes and Decasilanes

Abstract

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.

Syntheses and Molecular Structures of Liquid Pyrophoric Hydridosilanes

“…The higher homologues of these compounds are seldom used, since they are difficult to handle and pyrophoric. However, the chemistry of hydridosilanes has received a considerable revival in recent years due to their potential use as precursors for liquid phase deposition of silicon films . This approach promises significant reduction of processing costs in the manufacture of semiconductor devices .…”

“…However, the chemistry of hydridosilanes has received a considerable revival in recent years due to their potential use as precursors for liquid phase deposition of silicon films. [4][5][6][7][8][9][10][11][12][13][14][15][16] This approach promises significant reduction of processing costs in the manufacture of semiconductor devices. [4,17,18,19] Printing techniques have been applied to produce silicon thin-film transistors (TFT).…”

On the Potential of Silicon as a Building Block for Life

“…Boron (e.g., decaborane [12]) forms chains with itself, and in an alternation with carbon, nitrogen, or oxygen (heteroatoms), but forms clusters of atoms rather than smaller isolated molecules (a problem which is opposite to sulfur). Carbon (e.g., decane isomer) and silicon (e.g., decasilane isomer [15]), on the other hand, form chains with themselves, form chains in alternation with various heteroatoms, and can form diverse linear or branched structures. Out of the possible alternative scaffolding elements, silicon appears to be the most promising choice as a substituent for carbon in biochemistry.…”

“…Silanes (silicon analogues of hydrocarbons), both branched and unbranched [15], and diverse cyclosilanes (e.g., cyclohexasilane) are commonly known silicon analogues of hydrocarbons [36]. Polymeric siloxenes (cyclosilane rings with attached -OH groups) have no direct carbon analogue, but are reminiscent of functionalized graphenes [37].…”

“…Such solubility behavior is likely the result of the formation of strong hydrogen-bonded molecular complexes in solution [69,93,94]. Such enhanced hydrogenbonding abilities and increased acidity of silanols, relative to carbon analogues, have potentially Silanols, silanediols, and silatriols (13,14,15) are silicon-containing analogues of alcohols that are characterized by unusual solubility properties, often being similarly soluble both in water and other solvents, like hexane [89][90][91][92]. Such solubility behavior is likely the result of the formation of strong hydrogen-bonded molecular complexes in solution [69,93,94].…”