2. reacting the hydridosilane above with a suitable Periodic Group IA (alkali) or Group IIA (alkaline earth) metal or alloy in an amount of at least 1 equivalent of metal per equivalent of halogen in an inert atmosphere such as argon or nitrogen and in an inert diluent such as tetrahydrofuran or toluene for a period of time sufficient to provide the desired polyhydridosilane.