The cyclopentazolate anion, N-5(-), has been researched extensively over the years and detected in the gas phase more than a decade ago, but was only recently measured in solution. The process whereby aryl pentazole reduction leads to the production of N-5(-) is still not fully understood. Here, the production of N-5(-) in solution was investigated using isotopic labeling techniques while implementing changes to the synthesis methodologies. N-15 labeled phenyl pentazole produced appropriately labeled phenyl pentazole radical anions and N5- which, upon collision induced dissociation, produced the expected N-3(-) signals. Changing to higher purity solvent and less coated Na metal allowed for a much more rapid pace, with experiments taking less time. However, the best yields were obtained with heavily coated metal and much longer reaction times. Utilization of a vacuum line and ultrapure solvents led to no products being detected, indicating the importance of a sodium passivation layer in this reaction and the possibility that sodium is too strong a reducer. These findings can lead to better production methods of N-5(-) and also explain past failures in implementing aryl pentazole reduction techniques.