Cyclopentasilane is a cyclic compound of silicon and hydrogen with the chemical formula Si5H10.

Decachlorocyclopentasilane then has its chlorine replaced by hydrogen using lithium aluminium hydride.

Cyclopentasilane is a liquid at standard conditions, but can be frozen to crystals at 173K.

In gas form, those bond lengths, as measured by electron diffraction, increased to 2.342 Å.

[3] Cyclopentasilane is sensitive, and starts decomposing when heated over 84°C, when it loses hydrogen and polymerizes.