The formation mechanisms of silicon nitride and silicon nitrogen hydrogen films, both produced by chemical vapor deposition (CVD) techniques and widely used in electronic device fabrication, are poorly understood. Identification of gas-phase intermediates formed from starting materials, typically silane, ammonia, and/or nitrogen, is a critical step in assessing the interplay between gas and surface processes in film formation. Two potential intermediates in this process, HSiNSi and H3SiNSi, have now been detected in a molecular beam by means of rotational spectroscopy. Both molecules were produced in electrical discharges of CVD-like gas mixtures and are the most readily observed silicon-nitrogen-containing molecules in the 6-20 GHz frequency range, though neither has been the subject of prior experimental or theoretical studies. HSiNSi and H3SiNSi are likely formed from reactions involving the silanitrile radical (SiN, isoelectronic to CN), implying that similar gas-phase reactions may be involved in film growth.