Try adding Chlorine. 4 NH3 + 3 Cl2 → NCl3 + 3 NH4Cl
Safety:
Moderately toxic by inhalation. An irritant to the eyes, skin, mucous membranes, and a systemic central nervous system irritant. An explosive sensitive to impact, light, and ultrasound. The solid explodes on melting. The liquid explodes above 60°C. Concentrated solutions are also explosive. Explosive decomposition is initiated by contact with: concentrated ammonia, arsenic, dinitrogen tetraoxide, hydrogen sulfide, hydrogen trisulfide, nitrogen oxide, organic matter, ozone, phosphine, phosphorus, potassium cyanide, potassium hydroxide solutions, selenium, hydrogen chloride, hydrogen fluoride, hydrogen bromide, hydrogen iodide. Mixtures with chlorine + hydrogen are potentially explosive. Upon decomposition it emits toxic fumes of Cl− and NOx. See also CHLORIDES.