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 prepared in high yield from (H3Si)4Si and 3.5 equiv of SnCl4, while Si5H10 and an equimolar amount of SnCl4 afforded a mixture of ∼60% of ClSi5H9 (1) with polychlorinated cyclopentasilanes and unreacted starting material, which could not be separated by distillation. 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 liquid anhydrous HCl. All compounds were characterized by standard spectroscopic techniques. For Si–H derivatives, the coupled 29Si NMR spectra were analyzed in detail to obtain an unequivocal structural assignment. The molecular structures of 2–4 were further confirmed by X-ray crystallography.