Manganese bis(trimethylsilyl)amide Mn[N(Si(CH3)(3))(2)](2) was used as a convenient material precursor to prepare pure manganese nitride nanopowders with reaction-controlled average crystallite sizes. The precursor was first reacted with liquid ammonia under reflux conditions and the resulting by-product was pyrolyzed under an ammonia flow at temperatures in the range 150-900 degrees C. The powder products were characterized mainly by powder X-ray diffraction (XRD) diffraction, SEM/EDX examinations, and FT-IR and micro-Raman spectroscopies. In all cases, a pure phase of nanocrystalline eta-Mn3N2 was detected by XRD as the exclusive manganese nitride product. The compound's nanopowders were extremely reactive toward air. Upon oxidation, they formed either MnO for a relatively better crystallized nitride from higher synthesis temperatures or Mn3O4 after self-ignition of a poorly crystalline nitride from a lower synthesis temperature.