The industrial reduction of dinitrogen (N-2) to ammonia is an energy-intensive process that consumes a considerable proportion of the global energy supply. As a consequence, species that can bind N-2 and cleave its strong N-N bond under mild conditions have been sought for decades. Until recently, the only species known to support N-2 fixation and functionalization were based on a handful of metals of thesanddblocks of the periodic table. Here we present one-pot binding, cleavage and reduction of N-2 to ammonium by a main-group species. The reaction-a complex multiple reduction-protonation sequence-proceeds at room temperature in a single synthetic step through the use of solid-phase reductant and acid reagents. A simple acid quench of the mixture then provides ammonium, the protonated form of ammonia present in fertilizer. The elementary reaction steps in the process are elucidated, including the crucial N-N bond cleavage process, and all of the intermediates of the reaction are isolated.