Partial Halogenation Of Cyclic And Branched Perhydropentasilanes

The perhydropentasilanes (H3Si)(4)Si and Si5H10 were chlorinated with SnCl4 to give chlorohydropentasilanes without destruction of the Si-Si backbone. Tetrachloroneopentasilane (ClH2Si)(4)Si (2) was prepared in high yield from (H3Si)(4)Si and 3.5 equiv of SnCl4, while Si5H10 and an equimolar amount of SnCl4 afforded a mixture of similar to 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 MesSi(5)Cl(9) (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 MesSi(5)H(9) (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 Si-29 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.