Linear Phenylsilanes with PSi4P, PSi5P, and Si7 Backbones

Abstract

AbstractLinear 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.