Partial Halogenation of Cyclic and Branched Perhydropentasilanes

The perhydropentasilanes (H3Si)4Si and Si5H10 were chlorinated with SnCl4 to give chlorohydropentasilanes without destruction of the Si-Si backbone. Tetrachloroneopentasilane (ClH2Si)4Si (2) was prepd. in high yield from (H3Si)4Si and 3.5 equiv of SnCl4, while Si5H10 and an equimolar amt. of SnCl4 afforded a mixt. of ∼60% of ClSi5H9 (1) with polychlorinated cyclopentasilanes and unreacted starting material, which could not be sepd. by distn. The selective monochlorination of Si5H10 was achieved starting from MesSi5Cl9 ((3); Mes = 2,4,6-trimethylphenyl) or TBDMP-Si5Cl9 ((4); TBDMP = 4-tert-butyl-2,6-dimethylphenyl). 3 Or 4 was successfully hydrogenated with LiAlH4 to give MesSi5H9 (6) or TBDMP-Si5H9 (7), which finally gave 1 along with aryl-H and Si5H10 after treatment with an excess of liq. anhyd. HCl. All compds. were characterized by std. spectroscopic techniques. For Si-H derivs., the coupled 29Si NMR spectra were analyzed in detail to obtain an unequivocal structural assignment. The mol. structures of 2-4 were further confirmed by X-ray crystallog. [on SciFinder(R)]