Linear Phenylsilanes with PSi₄P, PSi₅P, and Si₇ Backbones

Abstract

Linear α,ω‐diphosphaoligosilanes were prepared starting from 1,5‐dilithiodecaphenyl‐n‐pentasilane, Li(SiPh2)5Li, and chlorodiorganophosphanes. The compounds 1,5‐bis(diphenylphosphanyl)decaphenyl‐n‐pentasilane, (Ph2P)Si5Ph10(PPh2), 1,5‐bis(di‐iso‐propylphosphanyl)decaphenyl‐n‐pentasilane, (iPr2P)Si5Ph10(PiPr2), and 1,4‐bis(di‐iso‐propylphosphanyl)octaphenyl‐n‐tetrasilane, (iPr2P)Si4Ph8(PiPr2), were obtained in moderate to good yields and characterized with IR‐, Raman‐, UV‐, 31P‐, 29Si‐, and 1H‐NMR spectroscopy. Single crystal structure analyses of these three silanes show all‐transoid conformations of the atoms along the phosphorus‐silicon backbone of the molecules in the solid state. The silicon‐silicon and the silicon‐phosphorus‐bonds are elongated. This is caused by the complete substitution of these molecules by sterically demanding phenyl‐ and i‐propyl‐substituents and effective σ‐conjugation along the main chains. Hexadecaphenyl‐n‐heptasilane, Si7Ph16, was prepared for comparison with the other three compounds. The latter one shows a long wavelength UV‐absorption in the same region as 1,5‐bis(diphenylphosphanyl)decaphenyl‐n‐pentasilane.

Challenges in the Synthesis and Processing of Hydrosilanes as Precursors for Silicon Deposition

“…[106,[125][126][127] Furthermore, it is possible to react the above-mentioned ring opening products with lithiated or halogenated boron or phosphorus compounds to produce linear and cyclic Si/B or Si/P compounds. [128][129][130][131][132][133][134][135] These could serve as precursors for "doped" silicon precursors for the direct deposition of doped silicon layers. However, it may be possible that the Si-B and Si-P bonds are also cleaved when the phenyl groups are removed.…”

“…In this case, the further reaction of the resulting terminally halogenated silicon chains is carried out with lithiated silicon compounds (Scheme 4). [106,125–127] Furthermore, it is possible to react the above‐mentioned ring opening products with lithiated or halogenated boron or phosphorus compounds to produce linear and cyclic Si/B or Si/P compounds [128–135] . These could serve as precursors for “doped” silicon precursors for the direct deposition of doped silicon layers.…”