This invention is directed to novel ammonolysis products including novel silazanes and polysilazanes characterized by repeating units of silicon-nitrogen in a polymeric compound having a reduced amount of Si—H bonds relative to the amount of Si—H bonds in the starting compound. Preparation of these novel ammonolysis products comprises introducing a starting compound containing at least one Si—H bond, such as a halosilane into a stoichiometric excess of anhydrous liquid ammonia wherein an ammonium halide is generated acting as an acid catalyst to provide an ionic and/or acidic environment for preparing the novel ammonolysis compounds. The prepared novel ammonolysis products are retained in a separate liquid-phase layer and distinct from the anhydrous liquid ammonia containing the ionized ammonium halide. Also provided are methods to purify ammonolysis products and to modify ammonolysis products by controllably increasing viscosity from a liquid to a solid and viscosities there between.