The bacterial catalyst for N2 fixation is a multi-subunit metalloenzyme comprising two electron carrier Fe proteins and the MoFe protein core. This complex catalyzes the reduction of N2 to NH3 and H2, with electrons provided by the Fe protein upon adenosine triphosphate hydrolysis. Our continued investigation of mechanism of nitrogenase activation and N2 binding via quantum chemical studies, combined with biochemical assays from Seefeldt and ENDOR measurements by Hoffman, revealed key features of the nitrogenase catalytic mechanism. Our studies highlighted that the thermodynamics of binding and activation of N2 takes place at the E4 state, which is activated by the accumulation of 4[e-/H+], with the concomitant reductive elimination of H2. We propose to extend our previous combined experimental/computational investigations to further explore the electronic rearrangements upon electron and proton delivery to the catalytic cofactor and upon N2 activation and reduction.