Method of making aluminum-free neopentasilane

A method of depositing a silicon-containing film on a substrate, the method comprising, introducing neopentasilane produced by contacting perchloroneopentasilane with a reductive effective amount of an alkali metal aluminum hydride in an alkylaluminum compound of formula RxAlCl3-x, where R is alkyl having from at least 5 carbon atoms, x is an integer from 1 to 3, and the alkylaluminum compound has a boiling point of at least 250° C., at conditions sufficient to reduce the perchloroneopentasilane, to form a reaction product mixture comprising the neopentasilane, and separating the neopentasilane from the product mixture to form a neopentasilane isolate, into a reactor with a substrate and, optionally, additional reactants under deposition sufficient conditions to form a silicon-containing film on the substrate, wherein the reductive effective amount is sufficient to reduce more than 98% (w/w) of the perchloroneopentasilane to the neopentasilane.